HUMAN ANATOMY by fjhuangjun

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									                        HUMAN ANATOMY
                               ZOO 3733c

                               Table of Contents


Chapter 1: Introduction                            page 2
Chapter 2: The Cell                                page 5
Chapter 4: The Tissues                             page 11
Chapter 5: The Integument                          page 17
Chapter 6: Osteology 1; Skeletal Tissue            page 21
Chapter 7 & 8: Osteology 2; The Skeleton           page 27
Chapter 9: Osteology 3; Arthrology                 page 34
Chapter 10: Myology 1; Muscle Tissue               page 38
Chapter 11: Myology 2; Muscles of the Body         page 44
Chapter 12: Neurology 1; The Fundamentals          page 47
Chapter 13: Neurology 2; The CNS                   page 55
Chapter 14: Neurology 3; The PNS                   page 67
Chapter 15: Neurology 4; The ANS                   page 75
Chapter 16; Neurology 5; The Special Senses        page 81
Chapter 17; Circulation 1; The Blood               page 93
Chapter 18; Circulation 2; The Heart               page 98
Chapter 19; Circulation 3; The Blood Vessels       page 103
Chapter 20: Lymphoid System                        page 108
Chapter 21: Respiration                            Page 112
Chapter 22: Digestion                              page 120
Chapter 23: Urinary System                         page 136
Chapter 24: Reproduction                           page 144
Chapter 25: Endocrine System                       page 156




                                         1
                        HUMAN ANATOMY
                           ZOO 3733c
        CHAPTER 1: THE ORGANIZATION OF THE HUMAN BODY
                              A. Introduction to Anatomy
1. Anatomy is the study of the human body, its structure and organization.
   a) It is a consideration of human morphology.
   b) Anatomy is divided into:
        1) Gross Anatomy - a study of those body structures which are
        visible to the “naked” (unaided) eye.
            a] It involves the use of observation and dissection.
            b] It can be further subdivided into:
                1] Regional Anatomy - all structures in a region of the body
                (ex; the abdomen).
                2] Systemic Anatomy - a study of the organs which make up a
                    system; the organs which serve a particular function.
                3] Surface Anatomy - a study of internal structures and how
                they relate to the integument.
        2) Histology / Microscopic Anatomy - a study of anatomy on the
        cellular level. It is a study of structures which can not be
        viewed with the naked eye.
            a] It involves use of the microscope.
        3) Embryological Anatomy - chronicles the changes which occur as
            the body develops from a zygote to a neonate.
        4) Developmental Anatomy - chronicles the changes which occur in
            the body throughout an individual’s life; from birth to death.
        5) Pathological Anatomy - studies the changes which occur in cells,
            tissues, and organs due to the effects of disease.
        6) Radiographic Anatomy - studies the internal anatomy via
        radiation (ex; MRI, X-rays, CAT Scans).
        7) Functional Morphology - studies the correlation between
        anatomical structures and their functions.

2. The Hierarchy of Structural Organization         {p3, Fig. 1.1}
   a) Organism - the highest level of organization (for our purposes), a
   living being.
   b) System/Organ System - a group of organs working together to
        perform a common action.
   c) Organ - a discrete structure made up of several tissues working
   together to perform a task.
   d) Tissue - a group of related cells working together to perform a task.
        1) There are four classes of tissue: epithelial, connective, muscle, &
   nervous.
   e) Cell - the basic unit of life.
        1) Cells can exist either singly (unicellular life) or in highly
        integrated groups (multicellular life).
        2) A cell can perform all of the functions essential for life to exist.
                                                2
           a] To accomplish this cells have a variety of functional units
           termed “organelles” (ex; nucleus, mitochondrion).
   f) Chemical Level - the atoms which make up an organism and their
   arrangement into molecules and macromolecules.
       1) There are four classes of macromolecules: carbohydrates,
           proteins, lipids, and nucleic acids.

                       B. An Introduction to Gross Anatomy
1. Anatomical Position                {p. 8, Fig. 1.3}
   a) Describe the “anatomical position”.
   b) Note: “right” and “left” refer to that portion of the anatomical
   subject, not to the viewer’s right or left.
2. Directional and Regional Terminology
   a) Directional Terminology {p. 9, table 1.1} -
       Describe the position of a structure relative to another structure to
   explain the terms: superior, inferior, anterior, posterior, medial,
   lateral, intermediate, proximal, distal, deep, superficial,
   cranial/cephalad, & caudal.
   b) Regional Terminology {p. 10, f. 1.4} -
       Regional terms are names for specific areas of the body.
       1) The two most fundamental are:
            a] Axial - the main axis of the body; the head, neck, and trunk.
            b] Appendicular - the appendages; the arms and legs.

3. Sections and Planes of the Body {p. 11, fig.1.5}
   a) Sections are cuts long a plane (i.e.; a flay surface).
       1) The section takes the name of the plane along which the cut was
           made.
           a] Ex; a transverse section is a cut along the transverse plane.
   b) There are three major planes of the body:
       1) Transverse Plane (aka; horizontal plane, cross section) - a plane
           running horizontally (left to right) dividing the body into inferior
       and superior portions.
       2) Sagittal Plane - a vertical plane dividing the body into left and
       right portions.
           a] Midsagittal (or Median Sagittal) Plane - runs along the midline
               of the body.
           b] Parasagittal Plane - runs at other than the midline of the body.
       3) Frontal Plane (aka; Coronal Plane) - a vertical plane which divides
   the body into anterior and posterior portions.
4. The Human Body Plan is consistent with the basic vertebrate body plan.
   a) The human body plan is consistent with the basic vertebrate body
   plan. It consists of:
       1) Bilateral Symmetry - most structures on the left half of the body
   mirror those on the right side.
           a] Most structures lateral to the midline are paired
               (ex; arms,eyes).
           b] Most structures along the midline are unpaired but divided into
           similar halves (ex; the heart).
       2) The Tube-Within-a-Tube Body Plan - The main body is said to be a
   tube and the digestive tube running through it is said to form the
       tube within a tube arrangement.
                                                3
       3) Segmentation - The outer tube of the body displays evidence of
       segmentation.
            a] Segments are repeating units of similar structure.
            b] Ex; ribs, rectus abdominis
       4) Dorsal, Hollow Nerve Cord - in the developing embryo, the CNS
       first appears as a hollow tube on the dorsum which develops into
       the brain and spinal cord.
       5) Notochord - a solid rod of cartilage located just deep to the
       developing CNS. It defines the main axis of the body.
            a] In “higher” vertebrates it is replaced during development by
            the vertebrae.
                1] Although vestiges of it remain as the intervertebral discs.
       6) Pharyngeal Pouches - These structures form clefts between the
       gills in more primitive vertebrates. In tetrapods they have
       become developed into other structures.
5. Abdominal Regions and Quadrants
   a) There are two basic strategies for the division of the abdominal
   region into subregions:
       1) The Four Abdominal Quadrants                         {p. 17, f. 1.12}
            a] Designated by two planes, one midsagittal and one transverse,
                dividing the abdomen into four quadrants: upper right, upper
                left, lower right, lower left.
       2) The Nine Abdominal Regions                   {p. 17, fs. 1.11}
            a] Designated by two equidistant parasagittal and two equidistant
       transverse planes which divide the abdomen into nine
            subregions: right hypochonriac, epigastric, left hypochondriac,
            right lumbar, umbilical, left lumbar, right inguinal/iliac,
       hypogastric/pubic, left iliac/inguinal.
6. Body cavities and Their Membranes                   {p. 14, f. 1.8}
   a) The body’s cavities are broadly divided into two:
       1) Dorsal Body Cavity - houses the CNS and is located within the
       skull and vertebral column.
            a] It is divided into:
                1] Cranial Cavity housing the brain.
                2] Vertebral Cavity housing the spinal cord.
            b] Its membranes are the meninges.
       2) Ventral Body Cavity - houses the viscera.
            a] It is divided into;
                1] Thoracic Cavity housing the heart, lungs, and mediastinum.
                     a} Further divided into the cardiac, pleural, and mediastinal
                         chambers.
                2) Abdominoplevic Cavity housing a variety of organs.
                     a} Separated from the thoracic cavity by the diaphragm.
                     b} It is subdivided further into the pelvic and abdominal
                     cavities.
            b] Its membranes are called serous membranes.




                                              4
                              CHAPTER 2: THE CELL
                                    A. Introduction
1. The cell is the basic unit of life.
   a) Cells were first discovered by Robert Hooke in the late 17th century.
   b) Cells perform all of the functions essential for life and these
   activities are facilitated by organelles.
2. The Cell Membrane (aka; plasmallema, plasma membrane) {p. 29, f. 2.2}
   a) The cell membrane separates the cell from the external environment
       allowing it to maintain its own internal environment.
       1) This is essential for it to conduct metabolism.
   b) Features of Cell Membrane Structure: The Fluid Mosaic Model
        1) The Fluid Mosaic Model, proposed by Singer and Nicholson in 1971,
            describes the cell membrane structurally as a phospholipid
            bilayer interdigitated by proteins and other lipids.
        2) The Phospholipid Bilayer - is the result of the amphipathic nature       of the
        phospholipid molecule.
            a] The phospholipid molecule has a hydrophobic “tail” and a
                hydrophilic “head”. That is what is meant by the term
            “amphipathic”.
                1] This feature causes the phospholipid molecules to
                spontaneously form a bilayer so that the “heads” are facing
                an aqueous environment externally or internally and the
                “tails” are in a water free zone.
                2] As a result of the amphipathic nature of the phospholipid
            molecule, the cell membrane will spontaneously form,
            maintain, and heal itself.
        3) Other lipids (ex; triglycerides, cholesterol) are integrated into
            the phospholipid bilayer and serve a variety of functions.
            a] Cholesterol serves to stabilize the “fluidity” of the cell
            membrane so it is not dependent on the kinetic energy of the
            molecules alone.
        4) Membrane Proteins
            a] Membrane Proteins make up almost 50% of the plasmalemma.
            b] They serve a variety of functions such as: recognition,
            receptors, and the transport of molecules.
            c] There are two classes of membrane proteins:
                1] Peripheral Proteins - are membrane proteins which do not
                extend into the hydrophobic portion of the phospholipid
            bilayer; they are not embedded in the membrane.
                     a} They are found on both the external and internal
                     environment facing surfaces (E face and P face,
                respectively) of the cell membrane.
                2] Integral Proteins - are membrane proteins which do extend
            into the hydrophobic portion of the phospholipid bilayer.
                     a} Transmembrane Proteins - are integral proteins which
                pass through the entire phospholipid bilayer.
   c) Functions of the Cell Membrane
       1) The cell membrane serves to separate the cellular components              from
       the external environment of the cell. This allows it to                maintain its
       own internal environment.
                                                5
   a] The cell membrane can not be a complete barrier however or
   the constituents and results of metabolism could not cross it.
       1] As a result, the cell membrane is described as being
       semipermeable (aka; selectively permeable) allowing some
   substances to cross but serving as a barrier to the
   transport of other substances.
2) Membrane Transport of Small Molecules
   a] Passive Transport - is the movement of substances across the
       cell membrane without the use of cellular energy (i.e.; ATP).
       1] Diffusion - is the net movement of molecules from an area
       of higher concentration to an area of lower concentration.
           a} This process requires no energy on the part of the cell.
               1} The energy comes from the kinetic energy of the
               molecules themselves.
           b} Osmosis - is the net movement of solvent molecules
       from an area of higher concentration to an area of lower
       concentration.
           c} Dialysis - is the net movement of solute molecules from
           an area of higher concentration to an area of lower
           concentration.
       2] Facilitated Diffusion - is the net movement of molecules
       from an area of higher concentration to an area of lower
       concentration but its occurrence is regulated by transport
       proteins.
           a} Again, the energy comes from the kinetic energy of the
           molecules themselves but membrane proteins regulate
       the event to maintain the cell’s metabolism.
   b] Active Transport - is the movement of molecules across the        cell
   membrane requiring cellular energy.
       1] ATP is required for this since:
           a} the molecules are being moved against the diffusion
           gradient
           b} or the molecules are too large to diffuse across the cell
           membrane.
3) Membrane Transport of Large Molecules
   a] Exocytosis(aka; secretion) - is the movement of large
   molecules out of the cell.
       1] The substance is enclosed in a membrane bound structure
       called a vesicle. This vesicle is then transported through
   the cytoplasm to the membrane where it fuses to the
   plasmalemma and extrudes the product into the external
environment.
   b] Endocytosis - is the movement of large molecules into the cell.
           1] Outward extensions of the plasmalemma surround and engulf
           the substance. The membrane then pinches off, into the
       cytosol, forming a vesicle.
       2] There are three types of endocytosis:
           a} Phagocytosis (“cell eating”)
           b} Pinocytosis (“cell drinking”)
           C} Receptor Mediated Endocytosis is similar to phagocytosis
           but uses membrane proteins to recognize the substance.

                                   6
                                   B. Organelles
1.The Nucleus
   a) The nucleus is a large double membraned organelle which contains
   the genetic blue-print of the cell.
       1) It averages 5um in diameter.
       2) Since our cells possess nuclei, we are said to be eucaryotic.
           a] Most of our cells have only one nucleus each and are termed
       uninucleated.
           b] Some of our cells possess more than one nuclei and are termed
           multinucleated (ex; skeletal muscle cells).
           c] Some of our cells lack a nucleus and are termed uninucleated
           (ex; RBCs).
   b) The Nuclear Membrane (aka; nuclear envelope) - is the double
       membraned structure which separates the internal environment of
   the nucleus, the nucleoplasm, from the cytoplasm.
       1) It is made up of two parallel oriented membranes.
       2) The nuclear membrane is even more selectively permeable than is
       the cell membrane so as to protect the DNA.
           a] The nuclear membrane possesses openings called nuclear pores
           which allow for the movement of material across the nuclear
       membrane.
   c) The Genetic Code is held in the nucleus.
       1) The genetic code is found on DNA molecules.
       2) DNA is tightly packed within the nucleus. {p. 37, f. 2.15, 2.16}
           a] The DNA is tightly wound about special proteins called histones
       forming a condensed unit termed the nucleosome.
           b] The nucleosome is further condensed into chromatin.
           c] During cell division the chromatin is even further condensed
       down into the chromosome.
                1] Chromosomes are composed of two chromatids held together
                by a centromere.
                2] Humans have 23 homologous pairs of chromosomes in each
                nucleus.
   d) The Nucleolus
       1) Nucleoli are dark staining structures located within the nucleus.
       2) The nucleolus is the site where the DNA is being read and copied
       to form mRNA (transcription).
           a] The mRNA will leave the nucleus and enter into the cytoplasm
           where protein synthesis will occur.
2. Ribosomes
   a) Ribosomes are very small organelles which are composed of two
   subunits, both being made up of proteins and RNA (rRNA).
       1) The two subunits come together when in contact with an mRNA
   molecule.
           a] They serve in translation where the genetic code is translated
           into an amino acid code in the process of protein synthesis.
       2) Ribosomes can conduct translation either freely in the cytosol or
   in association with another organelle, the endoplasmic reticulum,
   based on the nature of the protein being produced.
3. The Endoplasmic Reticulum {p. 35}
   a) The ER is an extensive, maze-like network of double walled cell
                                           7
   membranes running throughout the cytoplasm.
       1) It serves a variety of purposes but primarily connects the
   organelles and plasmalemma of the cell.
       2) Sometimes the ER will fold back on itself forming blind pockets
   termed cisternae.
   b) There are two classes of Endoplasmic Reticulum:
       1) Rough Endoplasmic Reticulum - this is ER to which ribosomes are
       attached giving it a studded or roughened appearance.
           a] This class of ER is involved in protein synthesis.
       2) Smooth Endoplasmic Reticulum - lacks ribosomes and so has a
       smoother appearance.
           a] This class of ER is involved in lipid metabolism, the storage of
           certain ions (ex; Ca), and poison detoxification.
4. The Golgi {p. 31, 32}
   a) The Golgi is another membranous organelle. It serves primarily in
   packaging the products of the cell.
       1) It has the appearance of stacks of double membraned structures.
   b) Transport vesicles carry the product to the cis surface of the Golgi
   where it enters the Golgi and is packaged and modified if necessary
   (ex; glycoproteins) . The product will then exit the Golgi from the
   trans surface.
5. Lysosomes
   a) Lysosomes are one such cellular product. They are membrane-bound
   organelles containing digestive enzymes.
       1) There are a wide variety of enzymes which have been identified in
   lysosomes.
   b) Functions in:
       1) digestion of foreign invaders and large substances
       2) self digestion during periods of cell starvation
       3) self digestion to remove dead cells.
6. Perioxysomes
   a) Perioxysomes are another class of organelles which are vesicles
   containing active chemical substances.
       1) The most important of these being peroxide forming enzymes
       which remove dangerous free radicals. They convert these free
   radicals into peroxide which can then be converted into water and
   oxygen.
       2) Some of these chemical substances are also used to detoxify
       certain poisons.
7. Mitochondria {p. 33}
   a) The mitochondria serve as the power plants of the cell and are the
   actual site of aerobic cellular respiration.
   b) Structure:
       1) They are peanut-shaped organelles heaving two membranes: an
       outer mitochondrial and inner mitochondrial membrane.
           a] The inner membrane is larger and arranged into folds termed
           crista.
           b] The space between the two mitochondrial membranes is termed
       the intermembrane space.
           c] The space enclosed by the inner mitochondrial membrane is
       termed the matrix.
   c) ATP, adenosine triphosphate, is produced in the mitochondria during
       the stages Kreb’s cycle and oxidative phosphorylation of aerobic
                                               8
   respiration.
   d) Mitochondria also contain their own DNA termed mitochondrial DNA.
       1) Mitochondrial DNA is inherited with the mitochondria from the
       mother.
8. The Cytoskeleton
   a) The cytoskeleton is, in effect, the cell’s skeleton.
       1) It serves to support the cell and assists in the movement both of
   the cell
            (ex; flagella) and of structures within the cell.
   b) In animal cells there are three recognized classes of cytoskeletal
   elements:
       1) Microfilaments - are the smallest of the three classes being
       ~7nm in diameter.
           a] They are solid rods composed of the protein actin.
                1] Actin serves in muscle contraction.
       2) Intermediate Filaments - are intermediate in size being ~8nm in
   diameter.
           a] These are also solid rods of protein.
       3) Microtubules - are the largest of the three classes being ~25nm in
       diameter.
           a] They are hollow tubes made up of dimer units of the protein
       tubulin.
           b] They make up a number of skeletal structure such as: flagella,
           cilia, spindle fibers, centrioles, and centrosomes.
                1] Centrioles are hollow structures made up of nine
                microtubules.
                2] Centrosomes (aka; microtubule organizing centers) are
                structures which produce and breakdown the cytoskeleton.
                    a} They are made up of two centrioles arranged
                    perpendicularly.



                              C. Mitosis and the Cell Cycle
1.The Cell Cycle is the life cycle of the cell. It runs from the birth of a
    cell until the completion of cytokinesis.
    a) It can be divided up into: Interphase, Mitosis, and Cytokinesis.
2. Interphase
    a) This is the longest stage of the cell cycle.
    b) It was once thought to be a period of rest but it is now known to be a
    period of great chemical activity in the cell.
         1) This cellular activity has allowed Interphase to be divided into
         three stages of distinctly different activity:
             a] G1 (the first Gap, or Gap 1, phase)
                 1] This is the last stage for nondividing cells (ex; muscle cells,
             neurons).
                 2] It is a period of protein synthesis producing the proteins
             required for DNA replication.
             b] S (Synthesis phase)
                 1] A period of DNA replication
             c] G2 (the second Gap, or Gap 2, phase)
                 1] This is another period of protein synthesis where the
                                                  9
                proteins required for mitosis are constructed.
3. Mitosis {p. 46 - 47}
    a) During this stage of the cell cycle the replicated DNA is sorted
segregated and divided to ensure that the two new cells produced
by cytokinesis have the right number and types of
chromosomes.
    b) Mitosis is divided into”
        1) Prophase
        2) Metaphase
        3) Anaphase
        4) Telophase
4. Cytokinesis
    a) This stage of the cell cycle is the division of the cytoplasmic
    component of the cell allowing for the production of two new
daughter cells.
        1) It occurs at the end of telophase when two new nuclei have
        been formed.




                                        10
                                CHAPTER 3: TISSUES
                                     A. Introduction
1. A tissue is defined as a group of closely associated cells which are
   similar in structure and perform related functions.
   a) Tissues also include nonliving materials, however.
        1) This acellular matter is termed extracellular material (ex;
   mineral component of bone tissue).
2. There are four classes of tissue: epithelial, connective, muscle, and
   nervous.


                                  B. Epithelial Tissue
1. Introduction to the Epithelia
    a) Epithelial tissues cover the body and lines the body cavities;
    covering all inner and outer body surfaces.
    b) Epithelial Tissues serve a number of functions:
        1) Protection - serve as the first line of defense of the body from
        foreign invaders
        2) Secretion - the release of products from cells (ex; glands)
        3) Absorption - the intake of molecules by the cells
        4) Sensory reception - involved in some of the special senses
            (i.e.; neuroepithelial cells)
        5) Filtration - the filtration of bodily fluids
        6) Ion Transport - the movement of ions throughout the body
    c) Special Features of Epithelium                   {p. 76, f. 4.1}
        1) Epithelium is composed mostly of epithelial cells in very close
        contact with one another.
            a] This close contact helps the epithelia to protect the body.
            b] The close contact is facilitated by intercellular junctions
            including:
                1] Desmosomes - cellular junctions which bind cells to one
                another.
                     a} Made up of protein plaques of the P faces of the opposing
                     cell membranes from which radiate microfilaments
                     anchoring the two cells together.
                     b} Leaves a small space (~5nm) between the two cells.
                2] Tight Junction - is another class of cellular junction binding
                cells together.
                     a} In this case the two cells are so close to one another that
                     their opposing cell membranes fuse in spots.
                         1} leaving no space between the cells
                3] Gap Junction - is a third class of intercellular junction.
                Unlike the other two., it serves to allow for communication
            between cells.
                     a} A specialized transmembrane protein runs through both
                     cell membranes serving as an ion channel.
        2) Epithelium is serparated from underlying tissues by a Basement
    Membrane.
            a] The basement membrane is an acellular structure made up by
                                                   11
           both the epithelium and the underlying c.t.
           b] Functions:
               1] It serves to bind and support the epithelium.
               2] It also allows for the regeneration of epithelia.
               3] It separates the epithelium from the c.t.
               4] It serves as a line of defense
       3) All epithelia has an underlying support of loose c.t.
       4) Epithelia, due to the tight packaging of its cells, lacks blood
       vessels and nerves.
           a] This is why epithelia must be supported by a loose c.t. having a
           good blood supply.
           b] This feature is unique to epithelia.
       5) Epithelia has a high regenerative capability.
           a] This allows it repair itself so as to better protect the body.
           b] C.T. has little regeneration (it decreases as you age) and
           muscle and nerve cells can not be regenerated after birth.
       6) Some epithelial cells have special surface modifications such a
   microvilli and cilia.
2. Epithelial Tissue Classification
   a) Epithelium can be classified based on two features: cell shape and
   number of cell layers.
       1) Classification Based on Cell Shape {p. 77, f. 4.2}
           a] Squamous Cells - are low, flattened cells. They are scale-like
           in appearance.
           b] Cuboidal Cells - are cube shaped cells (in 2D), of an equal
           height and width.
           c] Columnar Cells - are column shaped cells (in 2D). They are
           taller than they are wide.
       2) Classification based on Number of Cell Layers
           a] Simple - composed of one cell layer.
           b] Stratified - composed of more than one cell layer
           c] Pseudostratified - composed of one layer of cells of uneven
       height. Due to the height differences, they appear to be more
       than one cell layer but each cell is in contact with the basement
       membrane.
   b) Types of Epithelia                            {p. 79 - 82, fig. 4.3}
       1) Simple Squamous - composed of one layer of flattened cells.
           (ex; blood vessels, lymphatis vesels, serosa, glomeruli, alveoli)
           a] Mesothelium - epithelium lining the ventral body cavities and
       their associated organs.
           b] Endothelium - epithelium lining all the hollow organs of the
           circulatory system.
       2) Simple Cuboidal - a single layer of cube-shaped cells.
           (ex; small glands, ovary surface, kidney tubules)
       3) Simple Columnar - a single layer of columnar-shaped cells.
           (ex; lining of alimentary canal from stomach to anal canal)
           a] In some cases the cells possess cilia on their apical surfaces.
           These are termed simple ciliated columnar epithelium (ex;
           uterine tube).
       4) Pseudostratified Columnar - a single layer of columnar-shaped
   cells of varying height giving the false impression of being more
   than one cell layer in thickness.
           (ex; ducts of large glands, portions of the male urethra)
                                               12
           a] Includes pseudostratified ciliated columnar epithelium of the
       upper respiratory tract.
       5) Stratified Squamous - more than one layer of flattened cells.
           (ex; skin, linings of vagina, mouth, & esophagus)
           a] Found in areas subject to much abrasion.
           b] There are two types:
               1] Stratified Squamous Keratinized (ex; skin)
               2] Stratified Squamous Nonkeratinized (ex; esophagus)
       6) Stratified Cuboidal - more than one layer (usually 2 - 3) of cube-
       shaped cells.
           a] Rare (ex; portions of large glands such as the mammaries)
       7) Stratified Columnar - more than one layer (usually 2 - 3) of
           column- shaped cells.
           a] Rare (ex; portions of large glands such as the mammaries)
       8) Transitional - a stratified epithelium made up of variably shaped
       cells (ex; lining the urinary bladder).
           a] A unique tissue which allows for some distension/stretching.
3. Glands
   a) Glands are structures composed of epithelial cells which secrete an
   aqueous fluid product.
   b) They can be classified in two ways:
       1) Number of cells making up the gland -
           a] Unicellular Glands are made up of one cell.
           b] Multicellular Glands are made up of more than one cell.
       2) Mode of secretion -
           a] Exocrine Glands secrete their products into ducts.
               1] They can be either multicellular (ex; salivary glands) or
               unicellular (ex; goblet cells of the stomach).
           b] Endocrine Glands do not secrete their products into ducts.
               1] Aka; “the ductless glands”
               2] Their products are actually released into the blood stream
           for delivery to the target organ.
                    a} These products are called hormones.
               3] They can be multicellular (ex; pituitary) or unicellular.


                                C. Connective Tissue
1) Introduction
    a) Connective Tissues are an extremely diverse class of tissues ranging
    from bone to adipose to blood.
        1) C.T. is broadly subdivided into four main classes:
            connective tissues proper, blood, cartilage, and bone.
    b) C.T. serves a variety of functions including: connecting organs and
    cells, forming the skeleton, allow for the transport of gases and
    nutrients, and to protect the body via the immune system.
    c) Some diagnostic features of c.t. are:
        1) an extensive extracellular matrix.
            a] Unlike epithelium, c.t. cells are separated by the matrix.
            b] The nature of this matrix varies from type to type of c.t.
        2) a common origin. All c.t. are derived from an embryonic tissue
    called mesenchyme.
2. Connective Tissues Proper - this is a diverse group (divided further into   the
                                                13
two subclasses of loose and dense c.t.s) and may be best understood                 by
using one type, areolar c.t. as a model and comparing the others to it.
   a) Loose Connective Tissues
       1) Areolar Connective Tissue               {p.90, FIG. 4.14}
           a] It underlies most of the body’s epithelia and surrounds small
       nerves and blood vessels.
           b] The Extracellular Matrix of Areolar C.T.
               1] The Fibers -all three types of c.t. fibers are found in areolar
               c.t. and allow it to play a supportive role in organs.
                    a} Collagen Fibers - are the strongest and most abundant
                    class. they are able to withstand a great deal of tension.
                    b} Reticular Fibers - are branching fibers which can also
                    withstand tension, but to a lesser extent than can
               collagen, but are also more flexible/resilient than is
               collagen.
                    c} Elastic Fibers - are the weakest but most flexible of the
                    three fiber types. They are composed of the protein
               elastin.
               2] The Ground Substance - a material of varying consistency
               which is made up of constituents which are able to soak up
           interstitial fluid.
                    a} Interstitial Fluid is a deriviative of blood.
           c] The Cellular Component of Areolar C.T. - there are a variety of
               cell types found in areolar c.t.
               1] Fibroblasts - are immature c.t. cells which produce the
               fibers of areolar c.t.
                    a} N.B. - the suffix -blast means an immature c.t. cell.
                    typically this cell will be producing part of the c.t.’s
               extracellular matrix.
                    b} The fibroblast may continue to secrete fibers or mature
                    into an inactive cell type called the fibrocyte.
               2] Macrophages - nonspecific phagocytic cells derived from
               WBCs that range throughout the c.t.s.
               3] Mast Cells - inflammation fighting cells.
               4] Plasma Cells - antibody secreting B lymphocytes.
               5] Other WBC types such as neutrophils, eosinophils, &
               lymphocytes.
       2) Reticular Connective Tissue - {p.93}
           a} Reticular c.t. is much like areolar c.t. except that it has only
           one fiber type, the reticular fiber.
           b] Found in areas where some degree of stretch and strength is
           required (ex; spleen, bone marrow, lymph nodes).
       3) Adipose Tissue -                      {p.93}
           a] Adipose tissue serves to store nutrients, insulate the body, and
       protect the body from trauma.
           b} The cells of adipose tissue are called “adipocytes”.
   b) Dense Connective Tissues - have a much higher fiber content and a
       resulting lower cellular content than does loose c.t. It is a stronger,
   more resilient tissue than is loose c.t.             {p.94}
       1) Dense Irregular Connective Tissue - has its fibers (primarily
       collagen) running in a random or irregular pattern.
           a] Found in the dermis and the fibrous capsules of some organs
           such as the kidneys.
                                                  14
        2) Dense Regular Connective Tissue - has its fibers (again, primarily
   collagen) arranged into a regular repeating pattern.
            a] The collagen fibers are running parallel to one another.
                1] This gives it a great deal of tensile strength along one axis.
            b] ex; ligaments, tendons
        3) Elastic Connective Tissue - is a dense regular c.t. where the fiber
        type is the elastic fiber.
            a] It is found in areas requiring strength and flexibility (ex; vocal
        cords).
3. Blood                 {p. 97}
   a) The extracellular matrix of blood is very fluid and termed “plasma”.
   b) It has three classes of cells: wbcs, rbcs, and platelets.
   c) Blood serves in the transport of materials throughout the body and in
   the defense of the body.
4. Cartilage          {p. 95. 96}
   a) Cartilage is a firm but resilient c.t.
        1) Cartilage is found in the embryonic skeleton. most of it is
   replaced during development but some will remain (ex; tracheal
   rings, costal cartilages).
        2) It also forms the framework for areas of the body needing support
   but also flexibility (ex; nose, ears).
   b) The main cell of cartilage is termed the chondrocyte.
        1) Chondrocytes mature from chondroblasts which secrete the
        extracellular matrix of the tissue.
        2) The matrix however is too dense for the chondrocytes to exist in
   it directly. Instead they reside in fluid-filled cavities in the
   matrix termed “lacunae”.
   c) There are three classes of cartilage: hyaline, elastic, and
   fibrocartilage.
5. Bone              {p. 98}
   a) Bone is the densest of the c.t. due to minerals in its extracellular
   matrix.
   b) Bone serves to support and protect the body. It allows for movement
   and stores mineral ions.
   c) The main cell type of bone is the osteocyte.
        1) Osteocytes mature from osteoblasts which secrete the matrix of
   bone.
        2) As is the case with cartilage, the matrix of bone is too dense to
   allow osteocytes to reside in it directly and so they are located
   in lacunae.




                                    D. Muscle Tissue
1. Muscle tissue allows for the movement of the body and of structures              within
the body.
   a) To do this muscle cells, called myofibers, must be able to contract.
       1) This is facilitated by the cytoskeletal structures actin and
   myosin.
2. There are three classes of muscle tissue:
   a) Skeletal Muscle -       {p. 101}
                                              15
       1) Characteristics: striated, multinuceated, voluntary, associated
   with the skeleton
   b) Cardiac Muscle -       {p. 101}
       1) Characteristics: striated, 1 -2 nuclei, involuntary, branching
       cells, found only in the heart
   c) Smooth Muscle -        {p. 102}
       1) Characteristics: nonstriated, uninuceated, involuntary, associated
   with the hollow organs (ex; stomach) and glands



                                 E. Nervous Tissue
1. Nervous tissue serves to regulate and control bodily functions. {p. 103}
2. It contains two classes of cells:
    a) Neurons - the nerve cells which are modified to conduct information.
    b) Supporting Cells - a variety of cells which support and assist the
    neurons.
3. Nerve tissue makes up the nerves, spinal cord, and brain.




                                           16
              CHAPTER FIVE: THE INTEGUMENTARY SYSTEM
                                      A. Introduction
1. The integumentary system is composed of the epidermis, dermis,
    hypodermis, and associated organs such as hair, nails, sweat glands,           and oil
glands.
2. It comprises approximately 7% of our total weight and covers the body.
3. The skin is the epidermis and dermis.
    a) That is why the hypodermis is referred to as the “subcutaneous
    layer”.
    b) The skin varies in thickness throughout the varying regions of the
    body.
        1) It ranges from 1.5 to 4.0 mm.
        2) It is thickest on the soles and palms, forming what is called
        “thick skin”.
            a] All other skin is called “thin skin”. It is thicker on the dorsum
        than on the ventral surface.


                              B.The Skin and Hypodermis
1.The Epidermis               {p. 112, f. 5.1; p. 113, f. 5.2}
   a) The epidermis is a stratified squamous epithelium.
       1) To increase its protective functioning, this tissue is keratinized.
   b) The epidermis is composed of four cell types:
       1) Keratinocytes - are the principle cells of the epidermis.
           a] These epithelial cells arise from the deepest layers of the
           epidermis and mature as they move superficially.
               1] As they mature, their living portion is replaced by the
               protein keratin.
       2) Melanocytes - are the pigment producing cells of the epidermis.
           a] They produce the pigment melanin to protect from u.v. rays.
       3) Merkel Cells - are sensory cells believed to be involved in touch
   reception.
       4) Langerhans Cells - are macrophages which phagocytize foreign
   invaders of the skin.
           a] One of the few macrophages found outside of our c.t.s.
   c) The epidermis is arranged into layers based on the life stage of the
   keratinocytes present. There are 4 layers in thin skin and 5 layers in
   thick skin:
       1) Stratum Basale (aka; stratum germinativum)
           a] This is the deepest layer of the epidermis and rests on the
           basement membrane.
           b] It is composed of one layer of keratinocytes undergoing a great
           deal of mitosis to produce more cells.
               1] All of these keratinocytes are in contact with melanocytes
           which are transferring melanin to them.
           c] All four types of epidermal cells are found here.
       2) Stratum Spinosum
           a] This layer is named for an artifact. In early slides the cells of
       this layer had spine-like extensions due to over dehydration of
                                                17
       the tissue.
           b] This is several cell layers thick.
                1] Its keratinocytes are undergoing some mitosis but not to the
                extent of the stratum basale.
                2] Three of the four types of epidermal cells are present; only
                the Merkel cells are absent.
       3) Stratum Granulosum
           a] This layer consists of 3 to 5 layers of flattened keratinocytes
       beginning to undergo keratinization.
                1] The more superficial the layer, the greater the extent of
           keratinization.
                2] The more superficial layers are also too far removed from
           the underlying dermis to receive nourishment from the
           blood and so the keratinocytes are dead.
           b] The keratinocytes become invested with keratohyaline and
           lammellated granules of keratin.
                1] These granules give this layer its name.
                2] These granules will produce more keratin so that the cells
           become increasingly filled with it.
       4) Stratum Lucidum
           a] This layer is found only in thick skin.
           b] It is a translucent layer of flattened, dead, keratin rich cells.
                1] It has only keratinocytes.
       5) Stratum Corneum
           a] This is the most superficial layer of the epidermis.
           b] This is layer is called the “horny layer” because it is made up
       by many layers of flattened, dead, keratin rich cells.
                1] These cells are said to be “cornified”.
                2] Thee cells are being continuously shed (exfoliation) and
                replaced.
2.The Dermis                   {p. 112, f. 5.1}
   a) The dermis is the second, deepest, layer of the skin.
       1) It is deep to the epidermis.
       2) The dermis is a connective tissue layer.
           a] So it contains fibroblasts, fibrocytes, macrophages, mast cells
           and other c.t. type cells.
           b] Since it is a c.t., the dermis is well vascularized and
           innervated.
                1] The blood vessels of this layer exert control over body
                temperature through vasodilation and vasoconstriction.
       3) The dermis is said to bind the entire body together.
   b) The dermis is composed of two layers.
       1) The Papillary Layer
           a] This layer comprises the superficial 20% of the dermis.
           b] It is an areolar connective tissue.
           c] The papillary layer gets its name from its dermal papillae.
                1] Dermal papillae are finger-like extensions of the dermis
                which interdigitate with the epidermis and help to hold the
           two layers together.
       2) The Reticular Layer
           a] This layer comprises the deeper 80% of the dermis.
           b] It is a dense irregular c.t.
                1] The maze, or retinaculumn, of its collagen fibers give it its
                                                18
           name.
           c] The dermis varies in thickness from area to area causing the
       formation of tension lines (aka; lines of cleavage, Langerhans
       lines) in the skin.
1.The Hypodermis                  {p. 112, f. 5.1}
   a) The hypodermis is not, technically, considered to be part of the skin.
       1) It is found just deep to the skin.
           a] So it is also called the “subcutaneous layer” or “superficial
           fascia”.
   b) In humans the hypodermis is composed primarily of adipose tissue.
       1) It functions to:
           a] store fat
           b] anchor the skin to underlying structures
           c] allows for some degree of skin mobility
           d] insulation of the body.


                            B.The Structures of The Skin
1.Glands of the Skin - These are epidermal invaginations into the deeper
   layers of the integument.
   a) Sudoriferous Glands (aka; sweat glands)
       1) Sudoriferous glands are located on all body surfaces excepting the
   nipples and external genitalia.
       2) Functions:
           a] removal of nitrogenous wastes [slight]
           b] regulation of body temperature by cooling the body
       3) There are two types of sudoriferous glands:
           a] Eccrine Glands         {p. 120, f. 5.7b}
               1] These are the most numerous and widely distributed sweat
               glands.
               2] They are coiled, tubular glands which secrete their products
               onto the surface of the skin by a duct.
               3] They are active throughout your life time.
           b] Apocrine Glands
               1] These glands are much less numerous and distributed.
                    a} They are located in the anal, genital, and axillary regions
                    primarily.
               2] Their glandular openings are found at the base of hair
               follicles.
               3] They become active with the onset of puberty.
       4) Modified Sudoriferous Glands
           a] Mammary Glands
           b] Ceruminous Glands - apocrine glands modified to produce
               ceruminen, ear wax.
   b) Sebaceous Glands (aka; oil glands)                  {p. 120, f. 5.7a}
       1) Sebaceous glands are found throughout the skin in all areas except
       for the soles and palms.
       2) These glands produce sebum, oil and become active at puberty.
       3) Their glandular openings are found connected to hair follicles.
2. Hair            {p. 118, f. 5.4}
   a) Hair is a flexible strand made up of keratinized cells.
                                            19
       1) Unlike epidermal cells, the cells of hair have hard keratin.
   b) Functions:
       1) insulation from the cold
       2) protection from the effects of direct sunlight on the head
       3) protection from particulate matter entering the eyes/nose
       4) detection of insect pests.
   c) Structure:
       1)The hair can be divided into the shaft (the exposed portion) and the
   root (the portion embedded in the skin.
       2) Cross sectionally, hair can be divided into three concentric rings
   of slightly dissimilar cells: medulla, cortex, and cuticle.
       3) Hair Follicles are tubular invaginations of the epidermis from
       which the hair proper grows.
           a] Hair follicles extend from the epidermis into the dermis or
           even the hypodermis (in the scalp).
           b] Hair follicles have associated structures which aid the hair in
       performing its functions:
               1] Root Hair Plexus - a cluster of sensory nerve endings at the
               base of the follicle which allows for touch reception.
               2] Arrector Pili Muscle - a smooth muscle found at the base of
               the follicle which serves to erect the hair in response to a
           decrease in ambient air temperatures.
3. Nails            {p. 122, f.5.8}
   a) Both fingernails and toenails are modified extensions of the
   epidermis, rich in hard keratin, found at the distal edge of the digits.
   b) Parts:
       1) Free Edge - extends beyond the digit tip.
       2) Body - is the attached part.
       3) Root - the portion embedded within the skin of the digit.
       4) Nail Matrix - the site of nail growth.
       5) Nail Bed - a layer of epidermis upon which the nail sits.
           a] It gives rise to the nail matrix.
           b} It lacks the outer, keratinized layers of the epidermis.




                                           20
              CHAPTER 6: OSTEOLOGY 1 - SKELETAL TISSUE
                                        A. Cartilage
1. Introduction
    a) The early embryonic skeleton is composed mostly of cartilage.
         1) In more advanced vertebrates the cartilage is largely replaced by
         bone.
             a] In humans cartilage is found in the adult in:               {p.131}
                 1] the costal cartilages which connect the ribs to the sternum
                 2] the articular cartilages which cover the ends of most bones
                 and movable joints
                 3] the intervertebral cartilages located between the vertebrae
                 4] cartilages supporting the respiratory tubes (ex; tracheal
             rings)
                 5) cartilages of, and associated with, the larynx
                 6) cartilages of the pinna
                 7) cartilages of the nose.
2. The Nature Of Cartilage As A Tissue
    a) Cartilage is a firm but resilient tissue which is able to respond to
    pressure and to give support.
         1) This is due to its extracellular matrix which is firm due to its
         fiber and mineral content.
             a] Due to the firmness of the matrix, cartilage tissue is devoid of
         nerves and blood vessels.
                 1] Nutrients reach the chondrocytes (the mature cartilage
                 cells) by diffusion.
             b] Also due to the firmness of the matrix, the chondrocytes reside
         in lacunae, fluid filled chambers within the matrix.
             c] Chondroblasts, the immature cartilage cells, secrete the
             matrix.
    b) The cartilage organ will be surrounded by a layer of dense, fibrous
    c.t. called the perichondrium.
         1) The inner layer of the perichondrium contains chondroblasts
         which assist in the growth and repair of the organ.
         2) The fibrous outer layer of the perichondrium helps the cartilage
    organ to maintain its shape under pressure.
3. The Growth of Cartilage
    a) Cartilage displays two patterns of growth:
         1) Appositional Growth (“growth from without”) - chondroblasts in
    the surrounding perichondrium produce new cartilage tissue.
         2) Interstitial Growth (“growth from within”) - chondrocytes within
    the cartilage undergo mitosis and the resulting chondroblasts
    begin secreting new cartilage tissue.
    b) Cartilage growth, as is the case of all skeletal growth, ceases
    with maturity (middle to late teens).
         1) At this time the chondrocytes lose their ability to divide.
             a] Due to this, cartilage possesses little regenerative capability
         and so heals poorly.
                 1] Some healing is possible due to the chondrocytes ability to
                                                 21
               secrete new matrix.
4. There Are Three Classes of Cartilage:
   a) Hyaline Cartilage
       1) This is the most abundant and widely distributed type of cartilage
       2) It provides support with some flexibility and resiliency.
       3) Its matrix has only collagen fibers and these are arranged into
   thin strands giving a clear look to it.
       4) ex; costal cartilage, articular cartilage
   b) Elastic cartilage:
       1) Less widely distributed it is found in areas requiring support but
   also a good deal of flexibility.
           a] ex; epiglottis, pinna
           b] This flexibility is possible due to the presence of elastic fibers
   (in addition to collagen fibers) in the matrix.
   c) Fibrocartilage:
       1) Fibrocartilage often serves as a structural intermediate between
       hyaline cartilage and dense regular c.t.
           a] ex; where hyaline cartilage meets a tendon (eg; knee joint)
           b] Its microscopic appearance is also intermediate between
           hyaline cartilage and dense regular c.t. being composed of rows
           of chondrocytes arranged between prominent bundles of
       collagen.
       2) Fibrocartilage is found where both the ability to withstand
   pressure and tensile strength are required.


                                          B. Bone
1. Introduction
    a) Bone Tissue vs. Bone Organs
        1) Bone tissue is the dominant tissue of bones organs but bone
        organs contain more than simply bone tissue.
            a] It also contains blood vessels, lymph vessels, nerves, marrows,
            and other c.t.s.
    b) The endoskeleton serves a number of purposes:
        1) support (ex; pelvis supports the abdominal organs)
        2) protection (ex; skull protects the brain)
        3) movement (the bones act as the levers acted upon by skeletal
    muscles to produce movement)
        4) blood cell formation ( which occurs in red marrow housed within
    bone)
        5) mineral storage (for minerals such as calcium and phosphorus)
    c) Bones are classified based on their shape:        {p. 133, f. 6.2}
        1) Long Bones - length>width
            a] ex; femur, humerus
            b] long bones have a “shaft”
        2) Short Bones - length<width
            a] Short bones are generally cuboidal in shape (ex; carpals).
            b] A subdivision of the short bones are sesamoid bones.
                1] Sesamoid bones are short bones which are encased in
                tendons and ligaments. They do not articulate with the
                skeleton directly.
                2] ex; patella
                                               22
        3) Flat Bones -flattened, thin bones
            a] ex; ribs, many skull bones, ilium
        4) Irregular Bones - bones with an irregular shape
            a] ex; vertebrae, ethmoid, sphenoid
2. Types of Bone Cells
   a) Osteoblasts - are the immature bone cells they will produce the
   organic portion of bone matrix and mature into osteocytes.
        10 They are bone matrix depositing cells.
   b) Osteocytes - are the mature bone cells.
   c) Osteoclasts - are bone degrading cells.
        1) They will break down the matrix to release stored minerals (i.e.;
        calcium) back into the blood stream.
3. The Gross Anatomy of Bone
   a) All bone organs have two types of bone tissue; a thick, dense outer
   layer termed compact bone and an inner layer of sponge-like bone
   full of small openings termed spongy bone/cancellous bone.
        1) Compact Bone                {p.138}
            a] Although it may appear to be completely solid, compact bone is
            actually perforated with blood vessels, lymph vessels, and
            nerves.
                1] These vessels are a portion of a subunit called the Osteon or
            Haversian System.
                    a} An osteon appears as a group of concentric tubes
                    arranged in a cylinder along the long axis of the bone.
                        1} They act as weight bearing pillars within the bone.
                    b} Each of these concentric tubes has its collagen fibers
                    arranged parallel to one another within the tube.
                        1} Such an arrangement is called a lamella.
                        2} The collagen fibers of adjacent lamellae however are
                        arranged in alternating patterns (relative to each
                        other) so as to give more strength to the organ.
                    c} In the center of each osteon is the Haversian Canal.
                        1}The Haversian canal is also known as the Central Canal.
                        2} This canal allows a nutrient artery and vein to enter
                        into the bone tissue.
                            (a) The osteocytes are arranged into concentric rings,
                            the lamellae, around the Haversian canal so as to
                        receive nutrients and oxygen from the blood.
                        3} At right angles to the Haversian canals are
                        Volksmann’s Canals (aka; Perforating Canals) which
                    connect Haversian canals in neighboring osteons.
            b] The osteocytes reside in lacunae within the matrix due to its
            density.
                1] Unlike cartilage tissue, the matrix of bone is too dense to
            allow for the diffusion of materials to and from the cells.
                    a} That is why we see the perforation of blood vessels into
                    bone tissue.
                    b} It is also why we see radiating processes extending from
                    the lacunae called canaliculi.
                        1} These structures act as little irrigation canals
                        carrying materials between the Haversian canal and
                    the osteocytes.
        2) Spongy Bone (aka; diploe bone, cancellous bone) {p. 135, f. 6.3d}
                                                23
           a] Due to its numerous perforations, spongy bone does not require
           the osteon organization of compact bone.
               1] These perforations are crossed by tiny bridges of bone
               tissue called trabeculae.
               2] The spaces between the trabeculae are called
               intertrabecular spaces. They are not open spaces but filled
           with blood vessels and red marrow.
   b) The Structure of Bone Organs
       1) Long Bones            {p. 135, f. 6.3}
           a] Long bones have a distinct shaft with heads on either side.
               1] Epiphysis - the heads of long bones; these are expanded
               regions which allow for better articulation.
                   a} At the border between the epiphysis and the shaft is the
                   epiphyseal line.
                       1} It is the remains of a cartilagenous structure called
                   the epiphyseal growth plate from which long bones
                       grow in youth.
                            (a) The epiphyseal plate is composed of hyaline
                            cartilage.
               2] Diaphysis - is the term for the shaft of a long bone.
               3] Medullary Cavity (aka; marrow cavity) - is an area within
               the diaphysis devoid of bone tissue and filled with marrow.
                   a} There are two classes of marrow:
                       1} Red Marrow - found in the intertrabecular spaces it is
                       hemopoeitic tissue.
                       2} Yellow Marrow - found in the medullary cavity of
                       children and adults it is actually stored fat.
           b] Blood Vessels
               1] The two main blood vessels of the long bone are the nutrient
           artery and nutrient vein.
                   a} They enter the bone through the nutrient foramen on the
                   shaft of the bone.
           c] Membranes of the Bone Organ
               1] Periosteum - is a layer of dense, fibrous c.t. covering the
           outer surfaces of bone organs except at the articular
           cartilage.
                   a} It has an inner layer of osteoblasts and osteoclasts to
               allow for the remodeling and repair of the bone.
                   b} It is richly vascularized and innervated.
                   c} The periosteum is attached to the bone surface by thick
                   bundles of collagen called Sharpey’s Fibers or
                   Perforating Fibers.
               2] Endosteum - is the c.t covering the inner surfaces of the
               bone organ.
                   a} It lines the trabeculae, Haversian canals, and
                   Volksmann’s canals.
       2) The Structure of Short, Flat, and Irregular Bones {p. 136, f. 6.4}
           a] These three bone classes closely resemble long bone structure
           in that there is an outer layer of compact bone and an inner
       layer of spongy bone.
           b} However, structurally they differ from long bones in that they
       lack the epiphyses, diaphysis, and medullary cavity.
4. The Chemical Composition of Bone
                                                 24
   a) The organic component of bone matrix is called the Osteoid.
       1) The osteoid makes up ~ 35% of the mass of bone tissue.
       2) It serves to add tensile strength and some flexibility to the bone.
       3) The osteoid has a high collagen fiber content.
   b) The inorganic component of bone is termed the hydroxyapitate.
       1) It is made up of mineral salts, primarily calcium salts.
       2) It makes up the remaining ~ 65& of bone mass.
       3) It gives bone its hardness.
5. Bone Development (aka; Osteogenesis, Ossification)
   a) Osteogenesis begins at about the eight week of development in the
   embryo. It is when the cartilagenous skeleton precursor is replace
   with bone. There are two processes:
       1) Intramembranous Ossification - where the bones develop directly
       from mesenchyme.
           a] So these bones do not develop from a hyaline cartilage
           precursor.
           b] Bones that develop in this way are termed “membrane bones”.
                1] ex; many of the skull bones and clavicle
       2) Endochondral Ossification - where the bones replace a
       cartilagenous precursor.
           a] These bones are termed “endochondral bones”.
                1] ex; femur, humerus
       b) The Process of Intramembranous Ossification               {p. 140, f. 6.8}
       1) Unlike endochondral bones, membrane bones do not develop from a
       cartilage model but directly from the mesenchyme.
           a]This process applies to most of the skull bones and the clavicle.
       2) Procedure
           a] During the eighth week of development a group of mesenchymal
           cells differentiate into osteoblasts.
           b] The osteoblasts begin to secrete the osteoid.
           c] the newly forming tissue becomes mineralized (adding the
           inorganic component).
           d] The osteoblasts will then become osteocytes existing within
           their self-created matrix.
   c) The Process of Endochondral Ossification                      {p. 141, f. 6.9}
       1) This process applies to all of the other bones, the endochondral
       bones.
           a] These bones are first modeled by hyaline cartilage which will
       gradually be replaced by bone tissue.
       2) Procedure
           a] A bone collar forms about the diaphysis of the cartilage model.
                1] The perichondrium which surrounds the cartilage becomes a
                periosteum.
                2] This periosteum then lays down a collar of bone tissue.
           b] The calcification of cartilage begins at the diaphysis of the
           cartilage model.
                1] Chondrocytes at the center of the diaphysis enlarge and
                signal for the calcification of the cartilage matrix.
                2] However, as the matrix calcifies the diffusion of nutrients
                to the chondrocytes becomes impossible and the cells begin
                    to die.
                3] As a result, the cartilage in this central area begins to
                deteriorate.
                                                 25
c] A Periosteal Bud invades the diaphysis.
     1] As the cartilage deteriorates a cavity forms in the diaphysis
     which is invaded by the periosteal bud.
          a} The periosteal bus consists of a nutrient artery, a
          nutrient vein, osteoclasts and immature osteoblasts.
     2] The osteoblasts begin to secrete the osteoid around the
remaining fragments of calcified cartilage forming the
first of the bone trabeculae (the beginning of spongy bone
formation).
     3] By the third month the bone tissue has begun to appear both
     within and around the diaphysis forming the Primary
Ossification Center.
d] Formation of the medullary cavity
     1] So far during this process the epiphysis has kept its
     cartilage healthy so as to allow for rapid growth which
(allows the bone to lengthen).
          a} As the cartilage grows outwards, the cartilage which is
     left behind begins to calcify and deteriorate forming the
     trabeculae.
     2] Meanwhile the center of the diaphysis continues to
disintegrate forming the medullary cavity.
e] Ossification at the epiphysis
     1] Shortly prior to or after birth the epiphyses begin to ossify.
          a} Cartilage in the center begins to calcify and die.
          b} An Osteogenic Bud enters the epiphysis.
             1} An osteogenic bud is much like a periosteal bud being
             an artery, vein, osteoblasts, and osteoclasts.
          c} Spongy bone begins to form in the epiphysis.
          d} These areas are called the Secondary Ossification
          Centers.
     2] This leaves cartilage only at the epiphyseal plates and on
the articular surfaces.
          a] Further growth will occur at the epiphyseal plate.




                                  26
             CHAPTER 7 & 8; OSTEOLOGY 2; THE SKELETON

                               A. The Axial Skeleton
1. The axial skeleton includes the skull, vertebral column, and rib cage.
   a) It is composed of 80 named bones, most of these being in the skull.
   b) It serves to protect the CNS and thoracic organs and to support the
   head, neck, and trunk.
2. The Skull            {p.155 -167, p.168-9 Table 7-2}
   a) The skull is a complex structure composed of two sets of bones: the
   facial and cranial bones.
        1) For the most part these bones are flat bones.
        2) They are joined by interlocking joints called sutures.
   b) The Cranium/Cranial Bones
        1) Frontal Bone - a single, broad, flat bone which forms the forehead.
            a] The frontal bone also contributes to the anterior cranial fossa
        which holds the frontal lobes of the cerebrum.
        2) Parietal Bones - a pair of bones that form the bulk of the cranial
   vault.
            a] Where the parietal bones articulate with other cranial bones
        the coronal, squamosal, sagittal and lambdoidal sutures are
        found.
        3) Sutural Bones (aka; Wormian ossicles) - are small, unnamed bones
        found within sutures.
        4) Occipital Bone - a single bone which makes up the cranial base
        and the posterior cranium.
        5) Temporal Bones - a pair of bones found on the sides of the
        cranium.
        6) Sphenoid Bones - a singular, irregular shaped bone which makes up
   a significant portion of the cranial floor.
        7) Ethmoid Bone - an irregular bone located between the sphenoid
   and nasal bones.
   c) The Facial Bones
        1) Mandible - the singular bone of the lower jaw.
        2) Maxillary Bones - these paired bones form the upper jaw and the
        central portion of the face.
        3) Zygomatic Bones - the cheek bones, they join the temporal bones
        to form the zygomatic arch.
        4) Nasal Bones - form the bridge of the nose.
        5) Lacrimal Bones - form a portion of the medial orbital wall.
        6) Palatine Bones - form part of the roof of the mouth.
        7) Vomer - a singular, medial bone of the face.
        8) Inferior Nasal Conchae - paired bones locate in the nasal cavity.
3. Hyoid Bone           {p. 167, f. 7.12}
   a) The hyoid bone is located anterior to the cervical region and below
   the mandible.
        1) It is held in place by ligaments connecting it to the larynx and the
        attachment of certain tongue and neck muscles.
4. The Vertebral Column {p. 170, f. 7.13}
   a) The vertebral column is composed of 33 irregularly shaped bones
   called the vertebrae.
                                               27
        1) The vertebrae actually appear as 26 bones, 2 being composites of
        5 fused bones in the case of the sacrum and 4 fused bones in the
    case of the coccyx.
.       2) The vertebral column is able to maintain its position through the
    support of muscles and ligaments.
             a] The muscles include the erector spinae group and the
        iliocostalis.
             b] The ligaments are divided into two groups: the anterior and
             posterior longitudinal ligaments.
        3) Between the vertebrae are cartilagenous discs which serve to
        cushion and protect the spine called the intervertebral discs.
             a] The intervertebral discs are composed of:            {p. 171, f. 7.14}
                 1] a central nucleus pulposus
                 2] surrounded by the annulus fibrosis, twelve concentric rings
                 of fibrocartilage.
    b) The vertebral column has five major divisions:
        1) Cervical Vertebrae - the 7 vertebrae of the neck.
        2) Thoracic Vertebrae - the 12 vertebrae of the upper torso/thorax.
        3) Lumbar Vertebrae - the 5 vertebrae of the lower
        torso/back/abdominal area.
        4) Sacral Vertebrae or Sacrum - the 5 fused vertebrae which
        articulate with the pelvis.
        5) Coccageal Vertebrae or Coccyx - the 4 fused vertebrae of the
    vestigal tail.
    c) The Gross Anatomy of a Vertebra                {p. 172, f. 7.15}
        1) Centrum (or body) - the weight bearing portion of the vertebra.
        2) Vertebral Arch - the bony structure, posterior to the centrum,
    which encases and protects the spinal cord.
             a] The spinal cord passes through the Vertebral Foramen.
             b] The vertebral arch is actually a composite of 2 vertebral
             pedicles and 2 vertebral laminae.
             c] The vertebral arch has 7 processes radiating off from it:
                 1] (Dorsal) Spinous Process - the single posterior projection
             formed at the junction of the two laminae.
                 2] Transverse Process - Two lateral projections of the
             vertebral arch.
                      a} Both the spinous and transverse processes serve for
                 muscle and ligament attachment.
                 3] Superior Articular Process - a pair of processes which
                 extend superior to the vertebra so as to articulate with the
             vertebra above it.
                 4] Inferior Articular Process - a pair of processes which
                 extend inferior to the vertebra so as to articulate with the
             vertebra below it.
                      a} The points of articulation between the articulating
                      processes of two vertebrae are smooth surfaces called
                 articulating surfaces or facets.
             d] The space between the pedicles of two successive vertebrae
        are the intervertebral foramen which allow for the passage of
        the spinal nerves to and from the spinal cords.
    d) Regional Specializations in the Vertebrae {p. 174}
        1) Cervical Vertebrae
             a] These 7 vertebrae are designed to support and to move the head
                                                  28
           (as well as to protect the spinal cord).
           b] Due to their functional role the cervical vertebrae differ from
           the typical pattern:
               1] C3 -> C7 -
                    a} bifid spinous process
                    b} transverse foramen for the passage of blood vessels
               servicing the brain (i.e.; the vertebral arteries).
               2] C1 ; the Atlas -
                    a} Lacks a centrum and spinous process
                    b} It is basically a vertebral arch with two lateral masses
                    designed to support the skull.
               3] C2 ; the Axis -
                    a} It looks like a typical vertebra except that it has a
                    superiorly projecting process called the Dens or Odontoid
                    process.
                        1} The dens is designed to act as a pivot for the rotation
                        of the head.
                        2} Actually, the dens is the centrum of the atlas. It
                        separated from the atlas and migrated to, and fused to,
                    the axis during development.
       2) Thoracic Vertebrae
           a] These 12 vertebrae articulate with the ribs and so will be
           modified for this purpose.
               1] Each will have articulating surfaces, either Facets or
               Demifacets, for the attachment of the head of the ribs.
               2] Their transverse processes will also have facets to
           articulate with the rib tubercle.
                    a} Often the transverse process is elongated to allow for
               better articulation.
           b] Thoracic vertebrae will generally also have long, inferiorly
           pointing spinous processes which overlap to help stabilize
               our bipedal stance.
       3) Lumbar Vertebrae
           a] These 5 vertebrae are found in the region of the back exposed to
       the greatest amount of stress due to weight bearing. As a
   result they are thicker and have shorter, broader processes.
       4) Sacral Vertebrae          {p. 177, f. 7.18}
           a] These 5 vertebrae are fused together to form the Sacrum.
               1] The sacrum articulates with the pelvis and helps to support
               the weight of the trunk.
       5) Coccygeal Vertebrae           {p. 177, f. 7.18}
           a] Tese 4 vertebrae are fused together to form the Coccyx, the
           vestigial remnants of the vertebrate tail.
5. The Rib Cage and Sternum                     {p. 178}
   a) The Sternum
       1) The sternum is a composite of six bones and serves as the
       anterior point of attachment for the ribs via their costal
   cartilages.
       2) The sternum is made up of:
           a] Manubrium - a singular bone,it is the most superior portion of
       the sternum.
               1] It articulates with the first and second ribs as well as the
           clavicles.
                                                  29
           b] Body/ Blade/ Gladius - four fused bones making up the bulk of
           the sternum.
               1] It articulates with the second through the seventh ribs.
           c] Xiphoid Process - the inferiormost portion of the sternum.
               1] It is actually composed of cartilage until it ossifies at
               about the age of 40.
               2] It articulates with the body at the xiphisternal joint.
   b) The Ribs                                       {p. 167}
       1) The twelve pairs of ribs serve to protect the thoracic organs.
           a] The ribs are flattened, curved bones.
       2) The categories of ribs:
           a] True Ribs: R1-R7
               1] They are also called the Vertebrosternal Ribs since they
           attach directly to the sternum by their own costalcartilage.
           b] False Ribs: R8-R12
               1] These ribs attach to the sternum either indirectly or not at
           all. They can be further subdivided:
                    a} Vertebrochondral Ribs: R8-R10
                        1} They attach to the sternum indirectly by having their
                        costal cartilages attaching to the costal cartilage of R7.
                    b} Vertebral Ribs: R11-R12
                        1} These ribs do not attach to the sternum at all. They
                        are attached only at the vertebral column.


                            B. The Appendicular Skeleton
1. The appendicular skeleton is composed of the bones of the limbs and                 their
associated girdles.
   a) It serves primarily for movement.
2. The Upper Limb and Its Girdle
   a) The Pectoral Girdle (the clavicle and scapula)              {p. 187, f. 8.1 a}
        1) The Clavicle - is a slender, slightly curving flat bone which
        articulates anteriorly with the manubrium (the sternal
   extremity) and posteriorly with the scapula (the acromial
   extremity).
        2) The Scapula - is a flat, thin, triangular shaped bone found posterior
        to the rib cage (R2-R7) and the two scapula are separated by the
   vertebral column.            {p. 188, f. 8.2}
            a] Each scapula has three borders: superior, medial/vertebral, and
                lateral/axillary.
            b] The scapula articulates with the humerus at the Glenoid Cavity.
            c] The scapula has two hook-like processes, the Acromion and
        Coracoid Process, which are attached to the clavicle by
        ligaments.
   b) The Arm (the humerus)                                       {p. 189, f. 8.3}
        1) The arm, commonly called the “upper arm”, has only one bone, a
        long bone called the humerus.
            a] The proximal epiphysis of the humerus has a spherical head
        which articulates with the scapula at the glenoid.
                1] Due to its morphology this allows for rotational movement.
            b] The distal epiphysis has two points if articulation termed
            condyles.
                                                 30
               1] On the lateral condyle is the trochlea which articulates with
           the ulna.
               2] On the medial condyle is the capitulum which articulates
               with the radius.
   c) The Forearm (the ulna and radius)                            {p. 191, f. 8.4}
   1) This portion of the limb is composed of two parallel bones, the
   radius and ulna.
           a] they are in contact -
               1] at both epiphyses by the Radioulnar Joints.
               2] and along their lengths by the Interosseous membrane, a
           ligament.
       2) The Ulna
           a] The ulna is the larger of the two forearm bones and does the
       bulk of articulation with the humerus.
               1] To facilitate this it has two prominent projections on the
           proximal epiphysis which form a hinge joint:
                    a} The Coronoid Process
                    b} The Olecranon Process.
       3) The Radius
           a] The distal epiphysis is much wider than is the proximal (the
           opposite of the ulna) to better articulate with the carpal
       bones.
           b] The proximal epiphysis is shaped to allow for some rotation of
           the forearm.
   d) The Bones of the Hand             {p. 193, f. 8.6}
       1) The Carpus - the anatomical wrist
           a] The carpus is composed of eight bones loosely arranged into
       two rows of four bones each:
               1] proximal row - scaphoid, lunate, triquetral, pisiform
               2] distal row - trapezium, trapezoid, capitate, hamate.
       2) The Metacarpus - the “palm”
           a) The metacarpus is composed of five metacarpal bones, one to
           articulate with each finger.
       3) The Phalanges - the digits or fingers
           a] Each finger is termed a phalange.
               1] It is composed of three phalanx bones: distal, intermediate,
               and proximal phalanx.
                    a} The exception to this is the Pollex, the thumb which has
                    only two phalanx bones in it.
3. The Lower Limb and Its Girdle                                   {p. 195}
   a) The Pelvic Girdle (ilium, Ischium, and Pubis)                {p. 197, f. 8.7}
       1) Unlike the pectoral girdle which served to articulate and support
   the limb, the pelvic girdle must also support the weight of the
   superior body, especially the viscera.
           a] Due to this role, the pair of hip bones form a bowl-shaped
           structure called the Pelvis.
       2) The “hip bone” is anatomically known as the Innominate, os coxa,
       or Coxal Bone. It is made up of three bones which are fused
       together: ilium, ischium, and pubis.
           a] Ilium - is the superiormost bone of the innominate.
               1] The ilium consists of a “body” and the broad, flat “ala”.
                    a} Many muscles attach at the ala at its thickened superior
                    edge, the iliac crest.
                                                  31
            2] The ilium articulates with the sacrum via the sacroiliac
            joint at the auricular surface.
        b] Ischium - is inferior to the ilium and posterior to the pubis.
            1] The ischium is an “L”-shaped bone which can be divided into
            a thickened “body”, containing the ischial tuberosity, and
        the thin ramus, which articulates with the pubis.
        c] Pubis - the anterior portion of the innominate.
            1] It is a “V”-shaped bone having two rami; the superior ramus
            which articulates with the ilium and the inferior ramus
        which articulates with the ischium.
b) The Thigh         {p. 201, f. 8.9}
    1) The thigh is composed of only one bone, the Femur.
        a] In some ways the femur is comparable to the humerus:
            1] ball-like head at the proximal epiphysis to articulate with
        the girdle at the acetabulum
            2] a long bone
            3] distal epiphysis has two articular surfaces, the lateral and
        medial condyles, for articulation with the bones of the
        lower limb
        b] The femur also has a patellar surface for articulation with the
    patella.
c) The Patella (the knee cap)
    1) The patella is a triangular bone with one broad articular region
    divided into two articular surfaces for the lateral and medial
condyles of the femur.
d) The Leg           {p. 203, f. 8.10}
    1) The leg is composed of two parallel bones, the Tibia and Fibula.
        a] they are in contact -
            1] at both epiphyses by the Tibiofibular Joints.
            2] and along their lengths by the Interosseous membrane, a
        ligament.
    2) Tibia
        a] The tibia is much more massive than is the fibula.
        b] It articulates with both condyles of the femur proximally and
    with the talus of the ankle inferiorly.
    3) Fibula
        a] The fibula is a slender long bone which articulates with the
        tibia at both epiphyses and with the talus.
            1] The portion of the fibula articulating with the talus is the
                 lateral malleolus.
        b] The fibula does not bear any significant weight.
e) The Foot          {p. 204}
    1) The Tarsus (the posterior foot)
        a] The tarsus contains seven bones called the Tarsals which are
        designed to support the weight of the body and to allow for
    motion.
        b] The tarsal bones are:
            1] Talus - articulates with the lower leg and calcaneus.
            2] Calcaneus - the heel, the sight of attachment for the calf
        muscles.
            3] Cuboid
            4) Navicular
            5) Cuneiforms - there are three; medial, intermediate, and
                                             32
        lateral or first, second, and third cuneiform respectively.
2) The Metatarsus
    a] The metatarsus is made up of five small, long bones called the
        metatarsal bones.
3) The Phalanges - the digits or toes
    a] Each toe is termed a phalange.
        1] It is composed of three phalanx bones: distal, intermediate,
        and proximal phalanx.
             a} The exception to this is the Hallux, the big toe which has
             only two phalanx bones in it.




                                      33
                 CHAPTER 9: OSTEOLOGY 3; ARTHROLOGY
                                     A. Introduction

1. Arthrology is the study of joints.
   a) Joints are places where the components of the skeleton meet.
       1) Often it is bone to bone (ex; humerus to scapula) but it can also be
       bone to cartilage (ex; ribs to costal cartilage) or tooth to tooth
   socket.
   b) Joints are classified by two criteria: structure and function.
       1) Structural Classification:
           a] Fibrous Joints - the bones are connected by fibrous c.t., lack a
           joint cavity, have little or no movement.
           b] Cartilagenous Joints - the bones are connected by cartilage,
       lack a joint cavity, have little to no movement.
           c] Synovial Joints - the bones meet at a fluid filled joint cavity,
       highly mobile.
       2) Functional Classification:
           a] Synarthroses - immovable joints
           b] Amphiarthroses - slightly movable joints
           c] Diarthroses - highly movable joints (typically synovial in
           structure).



                                    B. Fibrous Joints
1. In fibrous joints the two bones are connected by fibrous c.t.
    a) They lack a joint cavity.
    b) In fibrous joints movement is either very limited (amphiarthritic) or
    nonexistant (synarthritic) due to the fibrous c.t. connection.
        1) There is one exception.
2. There are three types of fibrous joints:                 {p. 213, f. 9.1}
    a) Sutures:
        1) Sutures are fibrous joints having little fibrous c.t. The bones
        articulating at sutures are tightly bound together.
             a] The amount of fibrous c.t. will decrease as a process of aging.
                 1] At middle age the suture’s fibrous c.t. becomes ossified
             fusing the bones together. The fused suture is termed a
        Synostosis.
                 b] The tight binding of the bones is possible, even with little
             fibrous c.t., since the bones have wavy, interlocking edges.
             2) They are found only in the skull.
    b) Syndesmoses:
        1) Syndesmotic joints are fibrous joints where the fibrous c.t. is
        actually a ligament.
             a] The length of the ligament will determine the degree of
             mobility in a syndesmotic joint.
                 1] Ex; The greater length of the interosseous membrane
                 between the radius and ulna makes it a diarthritic joint
                 whereas the interosseous membrane between the tibia and
                                                34
             fibula are a amphiarthritic joint.
   c) Gomphoses:
       1) The gomphosis is a “peg-in-socket” joint exemplified only by the
   tooth and socket of the maxilla and mandible.

                                C. Cartilagenous Joints
1. In cartilagenous joints the two bones are connected by cartilage.
    a) They lack a joint cavity and show little to no movement.
2. There are two types:           {p. 214, f. 9.2}
    a) Symphysis:
        1) The symphysis is a cartilagenous joint where fibrocartilage is
        joining the two bones.
            a] Ex; intervertebral discs,pubic symphysis
        2) Note: hyaline cartilage is present on the articulating surfaces of
    the bones but it is the fibrocartilage which is binding them
    together.
    b) Synchondrosis:
        1) The synchondrosis is a cartilagenous joint where the bones are
    joined by hyaline cartilage.
            a]Ex; costal cartilage between R1 & manubrium, epiphyseal plates
        2) Synchondritic joints are synarthritic.

                                    D. Synovial Joints
1. In synovial joints a joint cavity is present. The overall structure makes         these
joints very diarthritic:                        {p. 215, f. 9.3}
    a) Articular Cartilage - hyaline cartilage encasing the ends of the bones
    which absorb compression.
    b) Synovial/Joint Cavity - a space between the two articulating bones.
        1) It holds a lubricant.
    c) Articular Capsule - it encloses the synovial cavity. It is composed of
    two layers:
        1) Fibrous Capsule - forms the outer layer of the articular capsule.
            a] It is composed of dense irregular c.t. and is an outgrowth of the
        periosteum from both bones.
            b] It serves to reinforce the joint.
        2) Synovial Membrane - forms the inner layer of the articular
    capsule.
            a] It is a layer of loose c.t. lining the inner surface of the capsule
            as well as all internal joint surfaces not covered by articular
        cartilage.
            b] It produces the lubricant of the joint.
    d) Synovial Fluid - the lubricant of the synovial joint.
        1) It is located within the articular capsule as well as within the
        articular cartilages (which it nourishes).
        2) Synovial fluid is a plasma filtrate produced by the blood vessels
    of the synovial membrane.
            a] It also includes glycoproteins secreted by the fibroblasts of
        the synovial membrane.
    e) Reinforcing Ligaments - they are either extensions of the fibrous
    capsule or distinct ligaments.
        1) There are two classes: intracapsular and extracapsular.
                                                   35
   f) Nerves and Blood Vessels
2. Based on the shapes of their articulating surfaces and type of motion
   there are six types of synovial joints:          {p. 224-5, f. 9.7}}
   a) Plane Joints - the articular surfaces are flat planes allowing for
   only short, gliding movements.
       1) ex; the carpals
   b) Condyloid Joints - a rounded articular surface of one bone fits into
   an oval concavity on another allowing for abduction-adduction and
   flexion-extension movements (ex; phalanx-metacarpal).
       c) Hinge Joints - a cylindrical articular process fits into a trough
       shaped surface allowing for only unidirectional angular
       movements.
           1) ex; humerus - ulna
       d) Saddle Joints - both articular surfaces are saddle shaped being
   both concave and convex. These joints are biaxial allowing for
   both abduction-adduction and flexion-extension movements.
           1) ex; carpal - metacarpal of the pollex
       e) Pivot Joints - the rounded end of one bone fits into a ring formed
       by another bone plus an encircling ligament. Allows for uniaxial
   rotational movement.
           1) ex; dens (of axis) and atlas
       f) Ball and Socket Joints - the spherical head of one bone fits into a
       spherical socket of another allowing for multiaxial motion.
           1) ex; humerus - scapula



                            E. Motions Allowed By Joints
1. There are three basic types of movements: angular, gliding, and rotation.
{p. 220-3
    a) Gliding - the simplest
    b) Angular Movements - increase or decrease the angle between bones.
          1) Flexion - a movement decreasing the angle between the bones{b,c}
          2) Extension - a movement increasing the angle between the bones.
          3) Dorsiflexion and Plantar Flexion of the Foot                       }
          a] Dorsiflexion - the toes point up
              b] Plantar Flexion - the toes point down
          4) Abduction - moving the limb away from the body midline.
          5) Adduction - moving the limb towards the body midline.
          6) Circumduction - moving a structure in a cone-like pattern.
    c) Rotational Movements - turning movements of a bone along its long
    axis.
          1) Medial Rotation - the limb’s anterior surface moves towards the
    body midline.
          2) Lateral Rotation - the limb’s anterior surface moves away from
    the body midline.
2. There are also “special movements” which are movements which do not
    fit into the aforementioned categories:
    a) Supination - turning the hand palm up
    b) Pronation - turning the hand palm down
    c) Inversion - turning the sole of the foot medially
    d) Eversion - turning the sole of the foot laterally
                                                36
e) Elevation - lifting the body part superiorly
f) Depression - lowering the body part inferiorly
g) Protraction - a nonangular movement of the jaw anteriorly
h) Retraction - a nonangular movement of the jaw posteriorly
i) Opposition - sequential movement of the thumb to touch each finger
tip with the tip of the thumb on the same hand.




                                       37
                CHAPTER 10: MYOLOGY 1; MUSCLE TISSUE
                   A. The Classification and Function of Muscle
1. Functions
   a) Muscle performs a number of functions such as movement,
   maintaining posture, joint stabilization, and heat generation.
   b) To perform its functions muscle tissue has some special (functional)
   features:
        1) Contractibility/Contractility - the ability for muscle to shorten
   its length. This ability allows muscle to act.
        2) Extensibility - the ability of muscle to be stretched back to its
   normal resting length after having been contracted.
        3) Elasticity - the ability of muscle to recoil and resume its resting
   length after having been stretched.
        4) Excitability - the ability of muscle to receive nervous stimulation
            (to cause contraction).
2. The Three Classes of Muscle
   a) Skeletal Muscle - attached to the skeleton, voluntary, striated,
   multinucleated.
   b) Cardiac Muscle - found only in the heart, involuntary, striated, have
        1 -2 nuclei per cell, branched cells.
   c) Smooth Muscle - found in the hollow organs, involuntary, nonstriated,
   uninucleated.
        1) NB1-> since both cardiac and smooth muscle are found in the
        hollow organs they are sometimes both referred to as “visceral
        muscle”.
        2) NB2-> since both cardiac and skeletal muscle are striated both
   are sometimes referred to as “striated muscle”.
3. Basic Muscle Structure
   a) Muscle cells are called “fibers” or “myofibers” due to their
   elongated appearance.
   b) The contractibility of muscle is facilitated by myofilaments, in
   particular actin and myosin, of the cytoskeleton.
   c) In muscle cells the plasmallema is called the Sarcolemma, the
   endoplasmic reticulum is called the Sarcoplasmic Reticulum, and the
   cytoplasm is called the Sarcoplasm.

                                   B. Skeletal Muscle
1. Skeletal muscle organs can truly be called organs since they are made           up of
more than one tissue type.
   a) Of course skeletal muscle tissue is predominant but there is also
   c.t.s, blood vessels, lymph vessels, and nerves.
   b) The c.t. component encases the myofibers, groups of myofibers, and
   the entire organ as well as having outgrowths which become tendons.
        1) Organization:                                        {p. 46, f. 10.1}
            a] Endomysium - a c.t. sheath surrounding each muscle cell or
            myofiber.
            b] Perimysium - a c.t. sheath surrounding groups of myofibers
        termed a Fascicle.
            c] Epimysium - a c.t. sheath surrounding the entire muscle.
                                             38
               1] The muscle is a group of fascicles.
               2] The epimysium will have extensions forming tendons.
   c) Each skeletal muscle is supplied by: one nerve, one artery, one or
   more vein; which will branch out to service the entire organ.
       1) In skeletal muscle, each myofiber is in direct contact with a
       nerve ending. This is termed the Neuromuscular Junction.
       2) Since the muscle will require a rich supply of oxygen and
       nutrients it will be well vascularized.
2. Muscle Attachment to Bone
   a) Origin and Insertion
       1) The majority of skeletal muscles run from one bone to another and
       when they contract one bone stays steady while the other moves.
           a] These points of attachment are called Origin and Insertion.
               1] The origin is on the bone which stays steady. }
               2] The insertion is on the bone which moves.
       2) Muscle can attach to bone either directly or indirectly.
           a] Direct Attachment - the muscle is close to the bone and its
       epimysium fuses directly to the periosteum of the bone.
           b] Indirect Attachment - the muscle is attached to the bone by
       extensions of the epimysium;
               1] such as in the case of tendons which is the most common
               2] or in the case of Aponeuroses which are broad tendon-like
               sheets used for the indirect attachment of muscle and bone.
3. Fiber Patterns and Muscle Shape                                     {p.69, f 11.3}
   a) Fascicles are visible to the naked eye and give the characteristic
   “fiber pattern” of skeletal muscle organs.
       1) Note: fiber pattern does not refer to myofibers but to groups of
   myofibers, fascicles.
   b) Different arrangements of fascicles are classified and reflected in
   muscle shapes and functions:
       1) Parallel - the long axis of the fascicles run parallel to the long
       axis of the muscle (ex; biceps brachii).
       2) Pennate - the fascicles are short and attach obliquely to a tendon
       which runs the length of the muscle. There are three types:
           a] Unipennate - the fascicles only attach to one side of the tendon.
               (ex; extensor digitorum longus)
           b] Bipennate - the fascicles attach to two sides of the tendon.
               (ex; biceps femoris)
           c] Multipennate - the fascicles attach to more than two sides of
       the tendon (ex; deltoid).
       3) Convergent - the origin of the muscle is broad and the muscle
       narrows as it approaches the insertion (ex; pectoralis major).
       4) Circular/Sphincter - the fascicles are arranged in concentric
       rings (ex; anal sphincter, orbicularis oculi).
4. Microscopic Anatomy of the Muscle Fiber                         {p. 249, f. 10.4}
   a) The skeletal muscle cell is an elongated, multinucleated cell having
   prominent dark bands called “striations”.
       1) These striations are due to myofibrils, the protein based
   contractile organelles of the myofiber.
           a] Myofibrils are groups of myofilaments which are composed of
           actin and myosin.
           b] Myofibrils are arranged into long rows of regular repeating
               segments called Sarcomeres.
                                               39
               1] In the sarcomere actin and myosin are arranged into
               partially overlapping sequences (when the cell is at rest).
   b) The sarcomere is the basic unit of contraction in the muscle cell.
       1) The boundaries at the two ends of the sarcomere are the Z lines or
       Z discs.
           a] The Z lines are the anchoring points of the actin filaments in
       the sarcomere.
               1] Actin filaments extend from the Z line towards the center of
               the sarcomere. They do not reach the center when the cell
           is at rest.
       2) In the center of the sarcomere extending towards the Z lines are
   the myosin, or thick, filaments.
           a] They do not reach the Z lines when the cell is at rest.
       3) The result is that, when at rest, we see areas of overlap and areas
       without overlap of the two types of myofilaments.
           a] The A band runs the entire length of the myosin filaments.
               1] It will have points which are actin free and points where the
               myosin and actin overlap.
           b] The H zone is found in the middle of the sarcomere and so in the
           middle of the A band.
               1] It is the portion of the A band which lacks actin, when the
           muscle is at rest.
           c] The M line is found in the center of the H zone. It is an area of
               the H zone where tiny extensions of the myosin filaments can
               be seen.
               1] These extensions connect adjacent myosin filaments to one
               another.
           d] The I bands are found at either end of the A band.
               1] I bands are actin pure - myosin free zones, when the cell is
               at rest.
               2] One I band actually overlaps over two adjacent sarcomeres
               and has the Z line in its center.
5. Muscle Contraction
   a) This striated arrangement of myofilaments allows for muscle
   contraction to occur according to the “Sliding Filament” or
   “Ratcheting Theory”.
       1) At the ends of the myosin filaments are knob-like extensions
       called myosin heads.
       2) During contraction the myosin heads, at both ends of the
   sarcomere, attach to the actin filaments and pull them towards
   the center.
       3) The myosin heads then release the actin and reattach to it further
       along its length pulling it further towards the center.
           a] This is done again and again, pulling the two Z lines closer
           together and shortening muscle length.
           b] When done, there is maximum overlap of the myofilaments and
           the muscle is contracted.
       4) Contraction requires calcium which is brought into the sarcomere
       by the sarcoplasmic reticulum.
   b) Muscle Extension occurs when the antagonistic muscle contracts
   stretching it out.
   c) Muscle contraction requires the organelles T-tubules and
       sarcoplasmic reticulum.
                                               40
       1) SER surround each myofibril and run the length of the muscle.
           a] They store and transport calcium.
               1] Calcium triggers the sliding of the filaments
       2) T-tubules are indentations of the sarcolemma running deep into
   the sarcoplasm.
           a] They carry nerve impulses towards the sarcomeres.
       3) The Triad      {p. 252, f. 10.8}
           a] The t-tubule is found at the A-I band junctions and is flanked
       on either side by perpendicular extensions of the SER called
       Terminal Cisternae. These three structures, the T-tubule and
       the two terminal cisternae, make up the triad of skeletal muscle.
           b] The terminal cisternae store calcium.
           c] When a nerve signals for the muscle to contract the impulse is
           carried by the T-tubules deep into the muscle cell.
               1] As the wave of depolarization travels down the T-tubule it
           forces calcium to flood out of the terminal cisternae into
       the sarcoplasmic reticuli.
               2] The calcium then binds to actin, freeing up the sites on actin
               where the myosin heads can attach, and allow contraction to
               occur.
6. There are Three Muscle Fiber Types              {p. 253, f. 10.9}
   a) Slow Twitch or Red Fibers - contract slowly/with little power but
   are high in stamina.
       1) They are red due to their high myoglobin content.
           a] Myoglobin is an oxygen storing compound.
       2) Slow twitch fibers depend on aerobic respiration.
   b) Fast Twitch or White Fibers - contract quickly/with much power but
   are low in stamina.
       1) They are white due to their low myoglobin content.
       2) Fast twitch fibers depend on anaerobic respiration.
   c) Intermediate Fast Twitch Fibers - contract quickly/with much power           Like
fast twitch fibers but are aerobic like slow twitch fibers.
       1) They are intermediate in strength and endurance.

                                  C. Cardiac Muscle
1. Cardiac muscle is found only in the heart where it forms the bulk of the        heart
wall in a layer called the Myocardium.               {p. 256, f. 10.10}
   a) It functions to pump blood throughout the circulatory system.
        1) It also contracts by the sliding filament mechanism.
2. Cardiac Muscle Fiber
   a) A diagnostic feature of cardiac muscle fiber is that these cells
   branch.
        1) These branches contact adjacent fibers through intercalated
        discs.
            a] Intercalated discs are composite intercellular junctions.
                1] They hold the cells together.
                2] And, through the use of modified gap junctions, they allow
                for an electrical impulse to be transmitted from one fiber
            to the next.
                    a} This allows for the coordination of the heart beat.
                    b} It also eliminates the need for the neuromuscular
                    junction (found only in skeletal muscles).
                                                41
       2) The spaces between adjacent muscle fibers is filled with
       endomysium.
   b) Each cardiac myofiber, as is the case with skeletal myofibers, are
   striated.
       1) Their myofilaments are also organized into myofibrils and
   sarcomeres.
           a] Cardiac sarcomeres are identical to skeletal sarcomeres.
   c) Unlike skeletal myofibers, cardiac myofibers show:
       1) instead of being arranged into simple cylinders, the cells branch
   and vary in diameter from place to place due to the higher density
   of mitochondria in these cells.
       2) Cardiac myofibers have a greater density of mitochondria due to
   their greater need for ATP to maintain the heart beat.
       3) Cardiac myofibers have a Diad instead of a triad.
           a] The diad is composed of one T-tubule and one terminal cisterna.
               1] The second terminal cisterna would be superfluous since
           calcium is also being supplied by the extracellular fluid.



                                   D. Smooth Muscle
1. Introduction             {p. 258, f. 10.11; p. 259, f. 10.12}
    a) Smooth muscle is found in the walls if the visceral organs.
    b) Its cells lack sarcomeres but it is also believed to contract by the
    Sliding Filament Mechanism. This has yet to be proven however.
2. The Smooth Muscle Fiber
    a) Smooth muscle cells are also termed “fibers” since they are also
    elongated.
         1) Unlike the other two classes, cardiac myofibers lack the striations.
            a] They do possess actin and myosin however they are not
            arranged into sarcomeres.
                1] Also the ratio of myosin to actin is lower in smooth muscle
                than in skeletal muscle.
                2] The interdigitating thick and thin myofilaments, instead,     are
                arranged so as to lay nearly parallel to the long axis of the
            myofiber.
                    a} Also running along the length of the myofiber are
                    intermediate filaments.
                        1} These intermediate filaments have short, globular
                        segments called dense bodies along their length
                            (a) The thin filaments anchor into these dense bodies so
                            they serve as Z discs.
                        2} Also along the length of the intermediate filaments are
                        structures called dense plaques.
                            (a) Dense plaques also anchor the actin filaments (so
                            they also act as Z discs) but in addition anchor on to
                            the collagen of the surrounding endomysium.
                        3} It is believed that this arrangement serves to anchor a
                        functional sarcomere and to allow for contraction by a
                    sliding filament-like mechanism.
    b) As in the other two classes, smooth muscle is signaled to contract
    by calcium.
                                                  42
        1) Calcium enters the smooth myofiber by the extracellular fluid and
        by the SER.
            a] However, the SER lacks terminal cisternae and is not
            associated with T-tubules.
                1] Both are lacking in smooth muscle.
                2] Instead the SER contacts the sarcolemma directly.
3. Smooth Muscle Tissue
    a) Smooth muscle tissue has many closely packed fibers interconnected
    by gap junctions.
        1) Between the fibers is endomysium.
            a] This endomysium is actually partially produced by the smooth
            muscle cells themselves since these cells secrete the matrix
        of their tissue.
            b] Smooth muscle fibers are not broken up into fascicles and so
        lack some of the c.t. sheaths of skeletal muscle.
    b) Smooth muscle is arranged into sheets, which is best since they line
        the hollow organs.
        1) Usually smooth muscle will be arranged into two perpendicular
        sheets one running the length of the organ (the longitudinal layer)
    and one running the circumference of the organ (the circular
    layer).
            a] These two opposing sheets may contract in alternating waves
            called peristalsis, pushing and squeezing the object through
        the organ.
4. Innervation of Smooth Muscle
    a) Single Unit Innervation - typically, a smooth muscle has the entire
    sheet innervated as a single unit.
        1) Only a few myofibers receive direct stimulation from a nerve
        ending. The impulse is sent through the entire sheet via gap
        junctions between fibers.
            a] This causes the entire sheet to contract as a single unit.
        2) On some occasions smooth muscle sheets may contract due to
    hormonal influences or even due to too much stretch on the fibers.
    b) Multi-Unit Innervation - in rare cases, each smooth muscle fiber is
    independently innervated.
        1) ex; arector pili muscle, ciliary muscle of the iris.




                                           43
 CHAPTER 11 MYOLOGY 2; SKELETAL MUSCLE DISTRIBUTION AND
    FUNCTION WITH SOME CONSIDERATION OF SMOOTH AND
                    CARDIAC MUSCLE
                    A. The Lever System of Skeletal Muscles
               - Students are responsible for reading over on their own -


                         B. Skeletal Muscular Interactions
1. Muscle can either work together (Synergistic) or against one another
   (Antagonistic) to perform a task.
2. Antagonistic Muscle Interactions
   a) An antagonistic muscle interaction requires two (or more) muscles
   producing opposite movements on a structure.
        1) The Agonist or Prime Mover produces a particular movement.
            a] Ex; the biceps brachii causes flexion of the forearm.
        2) The Antagonist opposes or reverses the movement of the agonist.
            a] Ex; the triceps brachii causes extension of the forearm.
            b] When the agonist is acting the antagonist is either at rest or
        nly slightly contracted so as to control the extent of motion
        produced by the agonist.
   b) The antagonist can also be the agonist for another motion and in that
   case it is the previous agonist which acts as the antagonist.
        1) ex; instead of forearm flexion, if we are discussing forearm
        extension the triceps brachii is the agonist and the biceps brachii
   is the antagonist.
3. Synergistic Muscle Interactions
   a) Most movements will also involve one or more muscles which assist
   the prime mover. These muscles are termed “synergists”.
        1) Synergists work either by adding force to a movement or by
        reducing undesirable extra movements.
   b) Ex; the quadriceps group (vastus lateralis, vastus medialis, vastus
   intermedius, and rectus femoris) work together to extend the lower
   leg.

                C. Development and Basic Muscle Organization
1. Muscle can be broadly divided into four classes based on embryological
   origin. (Note: all are derivatives of mesoderm)            {p. 271, f 11.4}
   a) Visceral Organ Musculature
       1) Visceral organ musculature refers to the muscles in the walls
       of the visceral organs.
       2) All visceral organ musculature arises from the splanchnic
   mesoderm.
           a] Splanchnic mesoderm then gives rise to both smooth and
           cardiac muscle.
   b) Trunk Musculature
       1) Trunk muscles are the muscles of the thorax, abdomen, and pelvis
       as well as some muscles of the head and most of the muscles of
   the neck.
                                             44
           a] All are skeletal muscles.
       2) Trunk muscles arise from Myotomes
           a] Myotomes are 30 to 40 segments of mesoderm found on either
           side of the notochord in the early embryo.
               1] The dorsal portions of the myotomes become the deep
               muscles of the back.
               2] The ventral portions of the myotomes become the muscles of
           the lateral and anterior trunk.
               3] The trunk muscles present in the head arise from three
               “head myotomes” which produce the muscles moving the
           eyes and tongue.
   c) Pharyngeal Musculature
       1) The skeletal muscle tissue surrounding the embryonic pharynx is
       termed “pharyngeal arch musculature”.
           a] Some of it will migrate to the head and neck becoming the
           muscles of facial expression and of mastication.
           b] Some of it will remain in the pharyngeal region as the skeletal
           muscle of the superior third of the esophagus.
   d) Limb Musculature
       1) Both the upper and lower limbs form from limb buds composed of
       somatic mesoderm.
           a] Some of the somatic mesoderm will form the limb’s bones and
           some will form the limb’s muscles.
               1] Extensor muscles arise from the mesoderm dorsal to the
                   limb bones.
               2] Flexor muscles arise from the mesoderm ventral to the limb
               bones.



                           D,. Naming Skeletal Muscles
1. There are several criteria used in the naming of skeletal muscles:
   a) Location - some names describe the location of the muscle.
       1) ex; intercostals
   b) Shape - some names describe the shape of the muscle.
       1) ex; deltoid, trapezius, rhomboideus
   c) Size - some names describe the size of the muscle.
       1) ex; major, minor, maximus, minimus, longus, brevis
   d) Direction - some names describe the direction in which the muscle’s
   fibers run. Such as:
       1) Rectus (“straight”) - the fibers are running parallel to the body
   midline.
       2) Oblique - the fibers run obliquely to the body midline.
       3) Transverse - the fibers are running at a right angle/perpendicular
       to the body midline.
   e) Location of Origin and/or Insertion - the muscle is named for the
   bone or bones which it is attached to.
       1) When both the origin and the insertion are present in the name of
       a muscle, the origin name comes first (ex.; brachioradialis).
   f) Action - the muscles are named for the action which the ellicit.
       1) ex; flexor, extensor, adductor, abductor, pronator, supinator.
2. Sometimes more than one of these criteria will be used to name the
                                              45
  muscle.
  a) ex; extensor carpi radialis longus.



                      E. The Skeletal Muscles of the Body
- The students are responsible for the muscles in the muscle tables on pages 276
through 331 -




                                           46
           CHAPTER 12: NEUROLOGY 1; THE FUNDAMENTALS

                     A. Basic Divisions of the Nervous System
1. The nervous system has three interrelated functions:
   a) Sensory Input - using millions of sensory receptors to monitor
   stimuli in both the external and internal environments.
   b) Integration - the processing and interpretation of the sensory
   input.
   c) Motor Output - the activation of “effector organs” to respond to
   stimuli.
       1) The effector organs include our muscles and glands.
2. The nervous system can be initially broken up into two major divisions
   which can be further subdivided:                         {p. 336, f. 12.1}
   a) Central Nervous System (CNS)
       1) The CNS consists of the brain and spinal cord.
           a] It is located in the cranium and the vertebral canal.
       2) The CNS is the integrating and command center of the body.
           a] It interprets the sensory input, integrates it, and determines a
       motor response.
   b) Peripheral Nervous System (PNS)                       {p. 337, f. 12.3}
       1) The PNS carries information to and from the CNS.
       2) The PNS can be divided into:
           a] The Sensory or Afferent Division - carries sensory information
           to the CNS from the sense receptors. It can be further divided:
               1] Somatic Sensory - sensory innervation of the outer portions
               of the soma (the body). It can be subdivided into:
                     a} General Somatic Senses - senses whose receptors are
                     spread widely throughout the “outer” body.
                        1} It receives information about pain, temperature,
                        pressure, touch, vibration, and proprioception (the
                     amount of stretch on muscles, joints, and tendons).
                     b} Special Somatic Senses - senses whose receptors are
                        concentrated in a small, specialized area.
                        1} They are the senses of vision, olfaction, audition, and
                        equilibrium.
               2] Visceral Sensory - sensory innervation of the inner body, the
           viscera, the heart, lungs, G.I. tract, etc. It can be subdivided:
                     a} General Visceral Senses - senses whose receptors are
                        widely distributed throughout inner body, the viscera.
                        1} It receives information about pain, temperature,
                        stretch, nausea, irritation, hunger, & chemical changes.
                     b} Special Visceral Senses - senses whose receptors are
                        concentrated in a small, specialized area.
                        1} There is only one sense considered in this category,
                        taste.
           b] The Motor or Efferent Division - carries motor information
           from the CNS from the sense receptors. It can be further
           divided:
               1] Somatic Motor - motor innervation of most of the skeletal
           muscles (excepting the pharyngeal arch muscles). It is also
                                                 47
          known as the Voluntary Nervous System. It can not be
          subdivided.
              2] Visceral Motor - motor innervation of the inner body, the
          viscera.. It can be subdivided:
                  a} General Visceral Motor - controls the cardiac and smooth
                  muscles. It is also known as the Autonomic Nervous
                  System (ANS) or Involuntary Nervous System.
                  b} Special Visceral Motor - it controls the pharyngeal arch
                      musculature, a special group of skeletal muscles.

                                   B. Nervous Tissue
1. Nervous Tissue, the main component of the nervous system, has a high
   cellular content.
   a) Over 80% of the tissue mass is cellular.
   b) There are two classes of cells in nervous tissue:
       1) Neurons - the cells which send the nerve impulses.
       2) Neuroglia - the supporting cells of the nervous system.
2. Neurons
   a) Neurons are the nerve cells proper.
       1) They are highly specialized cells which conduct the nerve impulse.

       2) Other characteristics of neurons include:
           a] nondividing - all neurons are produced prior to birth and are not
       replaced.
           b] long living - since they can not be replaced, neurons must last
           us for our entire lifetimes. (Note: there may be a possible
       exception in the cerebral cortex)
           c] very high metabolic rate - neuronal metabolism is very high so
           these cells require much glucose and oxygen.
   b) The Neuron and Its Anatomy                                        {p. 339, f. 12.4}
       1) The Cell Body (aka; nucleosome, perikaryon)
           a] uninucleated
           b] It contains the typical organelles of human cells as well as:
               1] Nissl or Chromatophilic Bodies - large clusters of RER and
               free ribosomes.
                   a} Nissl bodies serve to produce proteins to replace those
                   lost from the nucleoplasm and to repair the nucleolemma.
               2] Neurofibrils or Neurofilaments - bundles of intermediate
               filaments running between the Nissl bodies.
                   a} They serve to resist stress on the neuron.
           c] Most perikarya are located in the CNS where they can be
               protected by the vertebrae and skull.
               1] Those perikarya located outside of the CNS, in the PNS, are
               grouped together and surrounded by c.t. forming Ganglia.
       2) Dendrites
           a] Dendrites are one of the two classes of processes radiating out
           from the perikaryon.
           b] Dendrites typically serve as receptive sites, receiving the
           impulse and conducting it toward its perikaryon.
           c] Typically, dendrites are more numerous and show a greater
       degree of branching than does the second class.
           d] Dendrites contain most of the organelles found in the cell body
                                               48
        including extensions of the Nissl bodies.
    3) Axons
        a] Axons are the second class of cellular processes radiating out
        from the perikaryon.
        b] Typically, axons serve as impulse distributors sending the
        impulse from the perikaryon out to another cell.
        c] Each neuron, generally, has only one axon.
            1] The axon arises from a swollen region on the cell body
            called the Axon Hillock.
        d] Along with the other cytoplasmic organelles, the axon has a
    high component of neurofibrils, microtubules, and actin
    filaments.
            1] These cytoskeletal components add support to the axon
        (which can be of great length) and also aid in the transport
        of substances (through axonal transport).
        e] Axons branch to a much, much lesser extent than do dendrites
        but they may have some branches present:
            1] Axon Collaterals - rare branches which branch off at 90o
        angles to the axon.
            2] Telodendria - many branches occurring at the terminal end
            of the axon.
            3] Axon Terminals (aka; end bulbs, axonal boutons) - these are
            knob-like endings of the telodendria.
                a} These axon terminals synapse with the dendrites of other
            neurons, usually.
                    1} As a result, the contain Neurotransmitters.
c) Synapses                                             {p. 342, f. 12.8}
    1) Neurons communicate with other neurons and cells via synapses.
        a] Synapse - a junction, typically between neurons, which allows
        for the transfer of information.
            1] Information transfer is unidirectional across the synapse.
                a} This helps to control the direction of information flow.
        b] Some terminology:
            1] Presynaptic Neuron - the neuron sending the impulse to the
            synapse.
            2] Postsynaptic Neuron - the neuron receiving the impulse at
                the synapse.
                a} One neuron can serve as both at either of its ends.
    2) Types of Synapses
        a] Axodendritic Synapse - a synapse between the axon of the
        presynaptic neuron and the dendrite of the postsynaptic neuron.
            1] This is the most common type of synapse.
        b] Axosomatic Synapse - a synapse between the axon of the
        presynaptic neuron and the cell body of the postsynaptic neuron.
            1] Also fairly common, but much less so than is the above.
        c] Axoaxonic Synapse - a synapse between the axon of the
        presynaptic neuron and the axon of the postsynaptic neuron.
            1] rare
        d] Dendrodendritic Synapse - a synapse between the dendrite of
        the presynaptic neuron and the dendrite of the postsynaptic
            neuron.
            1] rare
        e] Dendrosomatic Synapse - a synapse between the dendrite of
                                            49
        the presynaptic neuron and the cell body of the postsynaptic
    neuron.
            1] rare
    3) Functional Structure of Synapses
        - Using the axoaxonic synapse as the model -
        a] The nucleolemma of the presynaptic and postsynaptic neurons
        are not actually in contact but are separated by the Synaptic
    Cleft.
        b] On the presynaptic neuron’s axon terminals are Synaptic
        vesicles containing neurotransmitters.
        c] On the postsynaptic neurolemma are receptor proteins which
    will recognize and bind to neurotransmitters.
            1] Typically, these receptor proteins will be attached to
            proteins serving as ion channels.
    4) The Synaptic Event
        - Using the axoaxonic synapse as the model -
        a] The Chemical Synapse
            1] The electrical impulse travels down the presynaptic axon.
            2] When it reaches the axon terminals the impulse triggers the
            exocytosis of the synaptic vesicles.
                a} So the synaptic vesicles fuse to the neurolemma and
                release neurotransmitter into the synaptic cleft.
            3] The neurotransmitters diffuse across the synaptic cleft and
            bind to receptor proteins on the postsynaptic neurolemma.
                a} Thee are a variety of neurotransmitters such as:
                acetylcholine, monoamines, neuropeptides, and certain
            amino acids.
            4] When the neurotransmitter binds to the receptor protein the
            ion channel attached to the receptor opens initiating the
        depolarization of the postsynaptic neurolemma.
            5] The neurotransmitters then are either broken down by
            membrane enzymes or return to the presynaptic axon.
        b] The Electrical Synapse
            1] The electrical synapse is much less involved then is the
            chemical synapse since the impulse itself is electrical to
        begin with.
                a} The impulse simply “jumps” the synaptic cleft and
                continues down the postsynaptic neuron.
            2] Electrical synapses are rarer than are chemical synapses.
d) Classifying Neurons - Neurons can be classified by either structure
or function.
    1) The Structural Classification of Neurons - is based on the number
    of processes radiating out from the neuron cell body.
        {p. 344, f. 12.10}
        a] Multipolar Neurons - these are neurons having three or more
    radiating processes.
            1] Usually only one of the processes is an axon and the rest are
            dendrites.
            2] By far the most common type of neuron accounting for about
            99% of all neurons.
        b] Bipolar Neurons - these are neurons having two radiating
        processes, one axon and one dendrite.
            1] These are rare neurons being found in association only with
                                           50
               some of the special senses.
           c] Unipolar Neurons - these are neurons having only one radiating
           process which serves as both an axon and a dendrite.
               1] These are also rare neurons making up the typical sensory
               nerves.
               2] Sometimes the unipolar neuron is also known as the
               Pseudounipolar Neuron.
                   a} They may actually originate from bipolar neurons whose
                   processes fused during development.
       2) The Functional Classification of Neurons - is based on the direction
       of information flow relative to the CNS. {p. 344, F. 12.11}
           a] Sensory Neurons (aka; Afferent Neurons) - send the impulse
       towards the CNS from sensory receptors of the PNS.
               1] Most afferent neurons are unipolar with their perikarya
               located in ganglia in the PNS.
                   a} The central process ,of their single process, serves as an
                   axon and carries the information towards the CNS.
                   b} The peripheral process ,of their single process, serves as
                   an dendrite and extends to the receptors to pick up the
               impulse..
           b] Motor Neurons (aka; Efferent Neurons) - carry the impulse away
       from the CNS out to the effector organ.
               1] Most motor neurons are multipolar and have their cell bodies
               located in the CNS.
           c] Interneurons (aka; Association Neurons) - lie between the
           sensory and motor neurons.
               1] Located only in the CNS.
               2] Most interneurons are motor neurons
3. The Neuroglia or Supporting Cells                             {p. 346, f. 12.13}
   a) The neuroglia are able to reproduce throughout our lifetimes.
   b) The neuroglia of the CNS are often called Glial Cells:
       1) Astrocytes
           a] Astrocytes are the most abundant of the glia.
           b] They have many radiating processes which are attached to
           neurons and blood vessels.
               1] These processes give the cells their name.
               2] These processes may serve to transfer nutrients from blood
               vessels to neurons.
           c] Astrocytes may also:
               1] help to regulate the ionic balance of the environment around
               the neurons.
               2] recycle neurotransmitters.
       2) Microglia
           a] These are the least abundant of the glial cells.
           b] They are also the smallest type of glial cell.
           c] Microglia are phagocytic cells which defend the CNS from
           foreign invaders and will also consume dead neurons.
       3) Ependymal Cells
           a] These glial cells are actually a simple, cuboidal, ciliated
           epithelium.
           b] The ependymal cells form a lining in the hollow spaces of the
       brain and spinal cord.
               1] ex.: ventricles, central canal
                                               51
           2] They allow for the circulation of cerebrospinal fluid
       throughput these hollow spaces and its diffusion into the
   tissues of the CNS.

    4) Oligodendrocytes
       a] These cells have processes which wrap around and insulate CNS
       neurons.
           1] The insulating material is termed Myelin.
           2] The processes of one oligodendrocyte can insulate several
           CNS axons.
c) The Neuroglia of the PNS is made up of two, fairly similar cell types.
    1) Satellite Cells
       a] These cells surround and support the perikarya of PNS neurons
       within the ganglia.
    2) Schwann Cells                                                  {p. 349, f. 12.15}
       a] These neuroglial cells surround the axons of PNS neurons
       forming the PNS’s myelin sheath.
           1] Myelin is a lipoprotein and is actually a modification of the
       Schwann cell membrane.
       b] Based on the interaction of the Schwann cells and the PNS
       neurons there are two classes of PNS axons recognized:
           1] Myelinated Axons - these are quickly firing neurons
       (120m/s) due to the fact that the Schwann cell membranes
           are wrapped in thick layers about the axon, insulating it.
                a} The Schwann cells insulating myelinated axons are
                wrapped around only that one axon but that axon will
                have many Schwann cells forming its myelin sheath.
                   1} The cell membrane of the Schwann cell grows around
                   the axon during development and continues too add
                layer after layer of myelin until both cells are mature.
                b} The myelin sheath of these axons is segmented in
                appearance and each segment is a separate Schwann cell
                membrane.
                   1} The space between adjacent segments/Schwann cells
                   is termed the Nodes of Ranvier.
                       (a) Nodes of Ranvier are regularly spaced at about
                           1 mm intervals.
                           (1) The reason that these are quick firing neurons
                           is that the impulse can jump from one node to
                       the next instead of having to depolarize the
                       neurolemma of the entire axon.
                                [a] This is called Saltatory Conduction.
           2] Unmyelinated Axons - these are slow firing neurons (0.5m/s)
           because large segments of the axon lack a myelin coating and
           the myelin coating of these axons is much thinner. Both
       decrease the amount of insulation afforded.
                a} Here one Schwann cell will service several axons.
                   1} Instead of wrapping around one axon the Schwann cell
                       has several axons invaginate into its cell membrane.
                       (a) So the myelin sheath is not nearly as thick
                       (b) Also in many places there are lengths of axon
                       which are not fully invaginated into the cell
                   membrane and so are uninsulated in that region.
                                              52
          c] Oligodendrocytes of the CNS have the same functional role as
          do the Schwann cells of the PNS.
4. Nerves
   a) A nerve is defined as many PNS axons arranged into parallel bundles.
       1) Nerves are organs.
       2) Most nerves contain both myelinated and unmyelinated axons.
       3) In the CNS many axons arranged into parallel bundles is termed a
       fiber or tract.
   b) The Organization of a Nerve                                      {p. 351, f. 12.17}
       1) Typically each axon is wrapped in its myelin sheath produced by
   its Schwann cells.
       2) Around the myelin sheath is a delicate layer of areolar c.t. called
   the Endoneurium.
       3) Groups of endoneurium ensheathed axons form bundles called
       Nerve Fascicles. Each nerve fascicle is wrapped up in its own c.t.
   sheath termed the Perineurium.
       4) Groups of fascicles are surrounded by a tough fibrous c.t. sheath
       called the Epineurium.
       5) There will also be blood and lymph vessels within the nerve organ
       to service its cells.

                                 C. The Nerve Impulse

1. The Impulse Event                                              {p. 343, f. 12.9}
   a) An unstimulated neuron is said to be in the Resting State.
       1) Its neurolemma is said to be Polarized meaning that the internal
   environment of the nerve is negatively charged relative to its
   external environment.
           a] Also, sodium cation concentrations are higher in the external
       environment and potassium cation concentrations are higher in
       the internal environment.
   b) When the nerve has become stimulated it leaves the resting state.
       1) Typically, the neuron become Depolarized (although some will
       become hyperpolarized instead).
           a] Depolarization is due to ion channels on the neurolemma opening
           up and unevenly exchanging sodium for potassium (3 for 2).
               1] This can occur either because an ion channel near the one in
               question has been opened or because the ion channel has a
               receptor protein attached to it which has bound to a
           neurotransmitter.
               2] Due to the uneven transport of cations, the polarity of the
           neurolemma has been reversed.
                   a} The internal environment is positively charged and the
               external environment is negatively charged relative to
           one another.
           b] This will trigger the Action Potential also referred to as the
           impulse.
   c) The impulse will travel rapidly down the axon at a constant strength.
   d) As the action potential passes a segment of the axon it will
   repolarize itself so as to return to the resting potential.

                                             53
                    CHAPTER 13: NEUROLOGY 2; THE CNS
                                       A. The Brain
1. Regions and Organization of the Brain
   a) The brain is organized into four regions:                   {p. 362, f. 13.4}
       1) Cerebral Hemispheres
       2) Diencephalon
       3) Brain Stem
       4) Cerebellum
   b) The arrangement of gray and white matter varies from one region of
   the brain to the next.
       1) Gray Matter vs. White Matter                            {p. 362, f. 13.5}
           a] Gray matter contains primarily unmyelinated structures such
       as cell bodies, unmyelinated axons, and dendrites.
           b] White matter contains primarily myelinated structures such as
           myelinated neuron processes.
       2) The brain does show the typical CNS pattern in the arrangement of
   gray matter and white matter but it also has some
   specializations.
           a] Typically in the CNS there is a central core of gray matter
           surrounded by white matter.
               1] This is the case in the spinal cord.
           b] During development, however, some of the neurons in the gray
           matter migrate into the white matter forming Brain Nuclei or
       Ganglia.
               1] This is the pattern throughout the brain.
           c] Also during development some of the neurons migrate out of the
           central core of gray matter, through the white matter, and
       relocate on to the external surface of the brain forming the
   Cortex.
               1] This occurs in the more highly evolved portions of the brain
               such as the cerebrum and cerebellum.
       3) The increased amount of gray matter in the brain helps the brain
   to perform its many functions.
           a] Since the gray matter contains many interneurons for
       processing information the brain can perform various complex
       neural functions.
   c) The Ventricle of the Brain                                  {p. 363, f. 13.6}
       1) Introduction
           a] Ventricles are cavities within the brain.
           b] Ventricles are lined with ependymal cells and are filled with
           cerebrospinal fluid.
           c] There are four ventricles in the brain. All are in continuous
       with one another and are in contact with the central canal of the
       spinal cord.
       2) The Four Ventricles
           a] The Lateral Ventricles (aka; first and second ventricles)
               1] These are a pair of C-shaped ventricles located within the
           cerebral hemispheres.
                   a} Due to their shape they have three “horns”: anterior horn,
                   posterior horn,and inferior horn.
                                               54
                2] The anterior portion of the lateral ventricles are quite close
                and are separated only by a thin median membrane called
           the Septum Pellucidum.
           b] The Third Ventricle
                1] The third ventricle is located in the diencephalon.
                2] It is connected to the lateral ventricles by the two
           Interventricular Foramen.
                3] The third ventricle narrows in diameter posteriorly (in the
           mesencephalon) forming the Cerebral Aqueduct which
           communicates with the fourth ventricle.
           c] The Fourth Ventricle
                1] The fourth ventricle is located in the “hind” brain between
           the cerebellum and the brain stem.
                2] It connects inferiorly to the central canal of the spinal cord
           (and medulla oblongata).
                3] The fourth ventricle has three apertures, or openings, which
                connect it to the subarachnoid space.
                     a} The subarachnoid space is a fluid filled space surrounding
                the entire CNS.
                     b} They allow the CSF of the ventricles to enter the
                     subarachnoid space.
                     c} They are: the two Lateral Aperatures and the Median
                     Aperature.
2. The Cerebrum                                                             {p. 364, f. 13.7}
   a) The cerebrum is composed of two cerebral hemispheres and makes up
   the bulk of the brain accounting for 83% of its mass.
       1) It is the superiormost portion of the brain.
       2) The cerebrum has a convoluted surface.
           a] Gyri - ridges of brain tissue, elevations.
           b] Sulci - shallow grooves or depressions in the surface of brain
       tissue.
           c] Fissures - deep grooves in the surface of the brain tissue.
                1] Transverse Fissure - separates the two cerebral
                hemispheres from the cerebellum.
                2] Longitudinal Fissure - separates the two cerebral
                hemispheres from one another.
       3) The cerebral hemispheres can each be divided into five major
       lobes:
           a] Frontal Lobe
           b] Parietal Lobe - separated from the frontal lobe by the central
       sulcus.
           c] Occipital Lobe - separated from the parietal lobe by the
           parieto-occipital sulcus.
           d] Temporal Lobe - separated from the frontal and parietal lobes
           by the lateral sulcus.
           e] Insula - buried deep within the lateral sulcus.
       4) In terms of gray matter vs. white matter the cerebrum can be
   divided into:                                      {p. 365 f. 13.8}
           a] Cerebral Cortex of gray matter
           b] Cerebral White Matter deep to the cortex
           c] Basal Nuclei (aka; basal ganglia, cerebral nuclei, cerebral ganglia)
           distributed throughout the cerebral white matter.
   b) The Cerebral Cortex                                            {p. 367, f. 13.10}
                                                 55
1) Introduction
    a] The cerebral cortex is the center of our consciousness.
    b] It is a layer of gray matter covering the exterior of the
cerebrum.
        1] It is only 2 to 4 mm thick but due to its numerous
        convolutions it accounts for 40% of the brain’s total mass.
    c] The cortex has Domains of specific cortical functioning.
        1] The domains, however, are not necessarily isolated and may
        overlap with one another.
2) The Motor Areas of the Cortex - are located in the posterior
    portion of the frontal lobe. There are four motor domains:
    a] Primary Motor Cortex (or Somatic Motor Area)
        1] It is located along the precentral gyrus (anterior to the
        central sulcus) of the frontal lobe.
        2] It controls the voluntary and skill requiring actions of the
    limbs, trunk, etc.
             a} So it initiates most skeletal muscle activity.
        3] The axons of the primary motor cortex run Contralateral
    meaning that the left hemisphere’s primary motor cortex
controls the muscular activity of the right body.
             a} These axons are the processes of large cerebral neurons
             called Pyramidal Cells.
             b} The axons extend throughout the brain as they carry
             motor information towards the spinal; cord and are
             called the Pyramidal Tract or Corticospinal tract.
        4] The human body is spatially represented on the primary
        motor cortex.                                {p. 368, f. 13.11}
             a} The term for this “body mapping” is Somatotropy.
    b] Premotor Cortex
        1] The premotor cortex is located immediately anterior to the
        primary motor cortex.
        2] It serves as a “memory bank” for learned or skill requiring
    motor activities.
    c] Frontal Eye Field
        1] The frontal eye field is located anterior to the premotor
    cortex.
        2] It controls the skeletal muscles producing movements of the
    eyes.
    d] Brocca’s Area
        1] Brocca’s area is located anterior to the inferior extension of
        the premotor cortex.
        2] Its purpose is not clear . . .
             a} It was once believed to control only the motor aspects of
             speech. That is now considered to be incorrect.
             b] Now it is believed to be the means that our brain uses to
                 preplan all of our voluntary motor activities.
                 1] Studies have shown it to become stimulated prior to
                    all motor activities.
3) The Sensory Areas of the Cortex - are located on the occipital,
    parietal, and temporal lobes. Each major sense has its own domain:
   a] Primary Somatosensory Cortex
       1] It is located posterior to the central sulcus on the
                                        56
    postcentral gyrus of the parietal lobe.
    2] It is involved in our conscious awareness of somatosensory
    input.
         a} The somatosenses are those of the outer body,
         particularly the skin, such as pain, pressure, touch,
         vibration, temperature and proprioception.
         b} It has the ability to determine precisely where on the
         body the stimulation was perceived.
             1} This is termed Spatial Discrimination.
    3} Like the primary motor area, the primary somatosensory
area displays:
         a} somatotropy
         b} contralateral
b] Somatosensory Association Area
    1] This domain is located immediately posterior to the
         primary somatosensory area.
    2] It serves to integrate different somatosensory inputs into a
    comprehensive evaluation of what is producing those
stimuli.
         a} This is possible due to heavy integration between the
         somatosensory association area and primary
         somatosensory area.
         b} In effect it serves as a memory bank allowing us to
         evaluate somatosensory input based on past experiences.
c] Visual Area
    1] The visual area is divided into the primary visual cortex and
    the visual association area.
    2] The Primary Visual Cortex - receives visual stimuli from
    the eyes.
         a} It is located on the extreme posterior and medial aspects
    of the occipital lobe.
    3] The Visual Association Area - interprets and evaluates the
    visual input received by the primary visual cortex based on
past experiences.
             a} Located over most of the occipital lobe.
d] Auditory Area
    1] The auditory area is also divided into the primary auditory
cortex and the auditory association area.
    2] The Primary Auditory Complex - receives auditory stimuli
from the ears.
         a} It is located on the superior edge of the temporal lobe
    mainly within the lateral sulcus.
    3] The Auditory Association Area - interprets and evaluates
the auditory input received based on past experiences.
         a} It is located posterior to the primary auditory complex.
e] Gustatory Complex
    1] The gustatory complex is located on the roof of the lateral
sulcus.
    2] It is responsible for our conscious awareness and
    interpretation of taste.
f] Olfactory Cortex
    1] It is located in the Piriform Lobe of the medial cerebral
    aspect.
                                      57
            2] The olfactory cortex is responsible for our conscious
            awareness and interpretation of smell.
    4) Association Areas of the Cortex - association areas make up the
remainder of the cortex. They integrate different senses and
experiences with past ones.
        a] We have already seen three: somatosensory association area,
        visual association area, and auditory association area.
        b] Prefrontal Cortex
            1] It is located anterior to the motor areas on the frontal lobe.
            2] The prefrontal cortex is responsible for personality and
            cognition (our ability to learn).
        c] General Interpretation Area (or Gnostic Area)
            1] It is ill defined and located on large areas the temporal,
            parietal, and occipital lobes.
                 a} However, usually it is only found on one hemisphere and
                 generally that is the left one.
            2] It serves to integrate all of our sensory input to give a
            comprehensive understanding of the situation.
                 a} It signals the prefrontal cortex which can allow for an
            emotional response as well.
        d] Language Comprehension Area - allows us to understand
            language.
        e} Visceral Association Area - allows for our conscious
        perception of visceral sensory information.
    5) The Hemispheres and Cortical Functioning
        a] It is currently believed that there is a division of labor
    between the two hemispheres.
            1] Remember that the two hemispheres are contralateral
            controlling opposite sides of the body.
            2] They specialize, to an extent, on the cognitive functions:
                 a} Left Hemisphere - responsible for logic, math, & language
                 b} Right Hemisphere - responsible for emotion, intuition,
            artistic skills and visual-spatial skills (in most).
c) Cerebral White Matter                                         {p. 374, f. 13.13}
    1) The cerebral white matter is composed of primarily of myelinated
    axons carrying information to and from the cortex as well as
between regions of the cortex.
    2) The axons are myelinated and bundled into large tracts. there
are three classes:
        a] Commissures
            1] The commissures are tracts of axons, called commisural
        fibers, running between the two hemispheres.
            2] ex; the corpus callosum (the largest) and the anterior
            commissure.
        b] Association Fibers
            1] These are tracts of axons connect regions within the same
            cerebral hemisphere.
                 a} Their lengths are determined by the distance between the
            two regions being connected.
        c] Projection Fibers
            1] These are tracts of axons serving to connect the cerebral
        cortex to other regions of the CNS.
            2] ex; pyramidal tract
                                              58
   d) Basal Nuclei                                                 {p. 375, f. 13.14}
       1) The basal nuclei are located within the cerberal white matter.
       2) They cooperate with the cerebra cortex to initiate and terminate
       movement and to control the intensity of a movement.
3. The Diencephalon                                         {p. 376, f. 13.15, 13.16}}
   a) The diencephalon is the central core of the forebrain and is
   surrounded by the cerebral hemispheres.
       1) It is (mostly) composed of three paired structures: thalamus,
       hypothalamus, and epithalamus.
       2) It borders the third ventricle.
       3) It is made up primarily of gray matter.
   b) The Thalamus
       1) The thalamus makes up 80% of the diencephalon.
       2) There are two thalamic hemispheres separated by the third
       ventricle and connected by the Intermediate Mass, a commissure.
       3) The thalamus serves as a relay center between the cerebrum and
       the rest of the nervous system.
           a] It both relays and processes information.
           b] The thalamus has 12 major nuclei, collectively termed Relay
       Nuclei, which allow it to perform this function.
   c) The Hypothalamus                                                     {p. 379, f. 13.18}
       1) The hypothalamus forms the inferior diencephalon.
       2) It is the main visceral control center of the body.
           a] This is also facilitated by 12 major nuclei.
           b] The hypothalamic functions include:
                1] control of the ANS
                2] center of emotional response
                3] regulation of body temperature
                4] has centers monitoring hunger and thirst
                5] circadian rhythms
                6] control of the endocrine system.
   d) The Epithalamus
       1)The epithalamus forms the dorsalmost portion of the diencephalon.
       2) It is composed of a tiny group of nuclei and the unpaired Pineal
       Gland.
           a] The pineal gland, or epiphysis cerebrei, is an endocrine organ.
                1] It secrete seratonin and melatonin which is also involved in
                our circadian rhythms.
4. The Brain Stem                         {p. 382-3, f. 13.20; p. 384, f. 13.21}
   a) Introduction
       1) The brain stem is composed of three regions; midbrain, pons, and
       medulla oblongata.
       2) The brain stem serves several general functions:
           a] It produces rigidly programmed, automatic behaviors necessary
       for survival.
           b] It serves as a passageway for nerve fibers running between the
           cerebrum and the spinal cord.
           c] It innervates the face and head being the point of origin for ten
           of the twelve pairs of cranial nerves.
       3) The brain stem is the least developed region of the brain and this
       is reflected in the organization of its white and gray matter.
           a] It has an arrangement which is very similar to that of the
           spinal cord having a central core of gray matter surrounded by
                                               59
    white matter.
        b] But it also has some nuclei embedded within that white matter.
b) The Midbrain
    1) The midbrain is located between the diencephalon and the pons.
    2) The Organization of the Midbrain
        a] The midbrain is divided into a “roof” and a “floor” by the
        cerebral aqueduct.
            1] The floor is made up of the Cerebral Peduncles which
            contains the fibers of the pyramidal tract.
            2] The roof is called the Tectum.
                 a} It has four clusters of nuclei embedded in its white
                 matter called the Corpora Quadrigemina. This can be
            divided into two groups of nuclei:
                     1} Superior Colliculi (or visual tectum) - responsible for
                     the visual reflexes.
                     2} Inferior Colliculi (or auditory tectum) - responsible
                     for the auditory reflexes.
        b] Surrounding the cerebal aqueduct is gray matter forming the
    Periaqueductal Gray Matter.
            1] The periaqueductal gray matter contains the cell bodies of
            cranial nerve 3 (oculomotor) and cranial nerve 4 (trochlear).
c) The Pons
    1) The pons is located between the midbrain and the medulla,
    anterior to the cerebellum and fourth ventricle.
    2) The pons contains:
        a] The nuclei of some of the cranial nerves close to the fourth
    ventricle. These cranial nerves are cn 5 (trigeminal), cn 6
    (abducens), and cn 7 ( facial).
        b] Pons Respiratory Centers which help to control breathing.
        c] The pyramidal tract, from the cortex, passes through the pons
        on its way to the spinal cord.
d) The Medulla Oblongata
    1)The medulla oblongata is the caudalmost portion of the brain stem.
        a] It connects directly to the spinal cord at the foramen magnum.
    2) Anatomy and Functions
        a] Pyramids
            1] The pyramids are located along the ventral midline.
            2] It contains the pyramidal tract (from the cortex).
                 a} The pyramidal tracts cross over in the medulla at the
            point known as the Decussation of the Pyramids.
        b] Inferior Cerebellar Peduncles
            1] These are fiber tracts connecting the cerebellum to the
            medulla oblongata.
            2] They are located along the lateral-dorsal portion of the
            medulla.
        c] Olives
            1] The olives are located immediately lateral to the pyramids.
            2] Each olive contains a wavy structure of gray matter termed
                 the inferior olivary nucleus.
                 a} It serves as a relay station for sensory information
                 traveling towards the cerebellum.
                     1} Especially for proprioceptive information.
        d] The medulla also contains the nuclei for the five inferiormost
                                               60
           pairs of cranial nerves.
                1] cn 8 -> vestibulocochlear - hearing and balance
                2] cn 9 -> glosopharyngeal - innervation of tongue and pharynx
                3] cn 10 -> vagus - innervates many organs in many areas
                4] cn 11 -> accessory - innervates some of the neck muscles
                5] cn 12 -> hypoglossal - innervates the tongue muscles
           e] It also houses much of the Reticular Formation which exerts
           autonomic control of:
                1] Cardiac Center - adjusts the force and rate of the heart beat
                2] Vasomotor Center - regulates blood pressure
                3] Medullary Respiratory Centers - regulates respiratory rate.
                4] It also has centers controlling other responses such as:
                sneezing, vomiting, hiccuping, swallowing, and coughing.
                5] These functions are also controlled by the hypothalamus
                which sends information to the reticular formation.
5. The Cerebellum                                                 {p. 386, f. 13.22}
   a) Introduction
       1) The cerebellum makes up 11% of the brain’s mass.
       2) It is located posterio-inferior to the cerebrum and dorsal to the
   pons and medulla oblongata.
   b) Structure and Function
       1) The cerebellum has two hemispheres.
           a] The two cerebellar hemispheres are connected by the vermis.
           b] Each hemisphere has three lobes:
                1] Anterior Lobe - coordinates body movements.
                2] Posterior Lobe - coordinates body movements.
                3] Flocculonodular Lobe - adjusts posture to maintain
           equilibrium.
       2) The cerebellum has three layers to it (as does the cerebrum).
           a] Cerebellar Cortex - an outer layer of gray matter.
                1] As in the case of the cerebral cortex, the cerebellar cortex
           is arranged into folds. These folds are called Folia.
                2] The cortex determines how smooth our body’s movements
                are.
           b] Cerebellar White Matter - the middle layer, it contains axons
           carrying information to and from the cerebellar cortex.
                1] The white matter has a branching, tree-like appearance to it
           termed the “arbor vitae”.
           c] Deep Cerebellar Nuclei - the inner layer, it contains the cell
           bodies belonging to the axons carrying information to and from
       the cerebellar cortex.
       3) The cerebellum communicates with other portions of the brain
       through the Cerebellar Peduncles.
           a] Superior Cerebellar Peduncles - connect the cerebellum to the
           midbrain and carry instructions from the cerebellum to the
       cerebral cortex.
           b] Middle Cerebellar Peduncles - connect the cerebellum to the
       pons and carry instructions from the cerebral cortex (motor) to
       the nuclei of the pons.
           c] Inferior Cerebellar Peduncles - connect the cerebellum to the
       medulla oblongata and spinal cord and carry information on
       balance and equilibrium.
   c) The cerebellum serves to receive and preview intended movements
                                                61
   ordered by the cerebral motor cortex.
       1) It coordinates the movements of the body.
       2) Unlike the cerebrum, the cerebellum is ipsilateral.
6. Protection of the Brain - comes from the bones of the skull, the
   meninges, cerebrospinal fluid, and the blood-brain barrier.
   a) Meninges
       1) The meninges are three c.t. membranes which serve to:
           a] cover and protect the brain
           b] enclose and protect the blood vessels of the brain
           c] contain the CSF.
       2) The Three Meninges                                          {p. 389, f. 13.25}
           a] Dura Mater
               1] The dura mater is the outermost and toughest of the three
               meningeal layers.
                    a} It is a tough, fibrous c.t.
               2] The dura actually folds back on itself forming two layers.
                    a} The two layers are:
                        1} The Periosteal Layer - it is actually part of the
                        periosteum of the cranial bones and so attaches to the
                        bones of the skull and is the more external of the two
                    layers.
                        2} The Meningeal Layer - the deeper layer, it is the true
                        external covering of the brain.
                    b} In most places, these two layers are fused together.
                        1} Where they are separate we find spaces between them
                        called the Dural Sinuses.
                            {a} The dural sinuses collect blood from the brain and
                            drain it into the internal jugular veins.
           b] Arachnoid Mater
               1] The arachnoid mater is the second layer of the meninges and
               is located deep to the dura mater.
                    a} Typically it is separated from the dura by a thin space
               called the Subdural Space.
                    1} The subdural space is filled with CSF.
               2] Also, it is separated from the third and deepest meninge,
           the pia mater, by another CSF filled space called the
           Subarachnoid Space.
                    a} The arachnoid mater is attached to the pia mater by
                    “web-like” extensions of the arachnoid.
                    b} This space holds the largest of the blood vessels
                    servicing the brain.
               3] The arachnoid mater also has superior extensions termed the
               Arachnoid Villi which enter into the dural sinuses.
                    a} The arachnoid villi allow CSF to enter into the dural
                    sinuses.
           c] Pia Mater
               1] The pia mater is the innermost meningeal layer and is in
               direct contact with the brain.
                    a} It actually clings to the surface of the brain.
               2] It is a delicate layer of c.t. richly vascularized by
               arterioles, venules, and capillaries.
   b) Cerebrospinal Fluid (CSF)                                       {p. 392, f. 13.28}
       1) CSF is located in and around the CNS.
                                                   62
       2) Functions:
           a] It helps to cushion the CNS.
               1] The brain actually floats in CSF.
           b] It nourishes the brain and removes wastes.
       3) CSF is actually a plasma filtrate.
           a] It is produced by special capillary beds in the brain called the
       Choroid Plexuses.
           b] Blood is filtered from the capillaries, of the choroid plexuses,
       and diffuses across the ependymal cells into the ventricles.
   c) Blood-Brain Barrier
       1) Blood borne toxins (such as urea, bacterial toxins, and mild toxins
       from food) are prevented from entering brain tissue by the blood-
   brain barrier.
       2) The blood-brain barrier refers to its capillaries which are very
       selectively permeable preventing many dangerous substances
       from reaching the brain cells.
           a] Primarily it is due to specializations of the endothelial walls
           in these capillaries.
               1] They have a more extensive tight junction component
               between adjacent endothelial cells making them the least
           permeable of the capillaries.
           b] The blood-brain barrier is not totally impermeable.
               1] Nutrients, gases, and wastes must be able to cross.
               2] Fat soluble molecules will also be able to diffuse across the
           endothelial plasmallema.
                    a} So substances such as nicotine, alcohol, and anesthetics
                    can enter the brain.

                                   B. The Spinal Cord
1. Introduction
    a) The spinal cord extends from the medulla oblongata, inferior to the
    foramen magnum, caudally to the level of L 1 or L2.
         1) It is located in the vertebral canal.
    b) It serves to connect the brain and PNS.
         1) So it is involved in all sensory and motor innervation inferior to
    the head.
         2) It is a two way conduction system, sending information to and
         from the brain.
2. Protection and External Structure
    a) Protection - the spinal cord has many of the same protective
    measures as does the brain. It is also protected by bone (the
    vertebrae), the meninges, and CSF.

       1) The Meninges of the Spinal Cord                        {p. 393, f. 13.29}
           a] Spinal Dura Mater
               1] The spinal dura mater is the outer layer of the meninges.
               2] Unlike the dura mater of the brain, it does not attach to the
               overlying bones.
                   a} As a result, there is a space between the dura and the
                   vertebrae called the Epidural Space.
                      1} The epidural space contains a network of blood vessels
                      and a layer of protective, cushioning fat.
                                               63
              b] Spinal Arachnoid Mater - very similar to that of the brain.
              c] Spinal Pia Mater - very similar to that of the brain.
         2) Cerebrospinal Fluid - the same fluid found in and around the brain.
    a] It is located in the central canal and around the spinal cord in
    the meninges.
              b] It is also produced by the choroid plexuses.
    b) The spinal cord does not extend the full length of the vertebral
    column.
         1) On average it ends at the level of L1 or L2.
         2) The pia mater and arachnoid mater end at S 2.
         3) At its inferior end the spinal cord tapers into the Conus
         Medullaris.
              a] The conus medullaris also tapers into a long filament of c.t.
         called the Filum Terminale.
                  1] The filum terminale anchors to the coccyx.
                  2] The filum terminale is covered with the pia mater.
    c) Thirty one pairs of Spinal Nerves radiate out from the spinal cord
    allowing for communication to and from the spinal cord.
         1) They pass through the intervertebral foramina.
         2) This is also manifest in those regions of the spinal cord serving
    the limbs:
              a] The Cervical Enlargement services the arms.
              b] The Lumbar Enlargement services the legs.
         3) A number of the spinal nerves radiate out from the conus
    medullaris into the inferior portion of the vertebral canal.
              a] They are collectively referred to as the Cauda Equina.
3. The Arrangement of Gray Matter and White Matter in the Spinal Cord
{p. 394, f. 13.30}
    a) Gray Matter
         1) The gray matter is primarily composed of unmyelinated axons,
    dendrites, and perikarya.
         2) The gray matter is surrounded by white matter in the spinal cord
    and in turn encloses the central canal.
         3) Spinal cord gray matter has an “H”-like shape.
              a] The Gray Commissure connects the two halves of gray matter.
                  1] It is like the bar on an H.
                  2] It has the central canal inside it.
              b] There are a pair of posterior arms called the Posterior or
                  Dorsal Horns.
                  1] These horns are composed of interneurons receiving sensory
                  information from the PNS.
                       a} These sensory neurons have their perikarya in the PNS in
                       a ganglion called the Dorsal Root Ganglion.
                       b} So the dorsal horns process sensory information.
                           1} This sensory information is divided into somatic and
                           visceral sensory.
              c] There are a pair of anterior arms called the Anterior or
         Ventral Horns.
                  1] These horns have the cell bodies of motor neurons whose
                  axons are extending out towards the effector organs.
                       a} So the ventral horns process motor information.
              d] In the thoracic and superior lumbar portions of the spinal cord
              the gray matter also has small Lateral Horns.
                                                  64
                1] As is the case for the ventral horns, the lateral horns
                contain the cell bodies of motor neurons.
    b) White Matter
        1) Spinal cord white matter is primarily composed of myelinated
        axons.
            a] These axons are carrying information between the brain and
        spinal cord and between different portions of the spinal cord.
                There are three classes of axon tracts in the spinal cord:
                1] Ascending Tracts
                    a} Most carry sensory information from the receptors to the
                brain.
                2] Descending Tracts
                    a} Most carry motor information from the brain to the
                    effector organs.
                3] Commissural Tracts
                    a} These tracts carry information from one side of the
                    spinal cord to the other.
3. Informational Pathways; The Spinal Tracts                       {p. 398, f. 13.33}
    a) General Information
        1) Most spinal tracts decussate at some point along their course.
        2) Most consist of a chain of 2 or 3 neurons which contribute to
        successive tracts along the pathway.
        3) Most tracts display some degree of somatotropy in that they have
            specific regions/specific tracts to deal with specific regions of
        the body.
    b) Ascending Pathways                                          {p. 398, f. 13.33}
        1) These are sensory pathways conducting impulses cranially by
        means of 2 or 3 neuron long chains.
            a] The neurons are termed: First Order, Second Order, and Third
            Order Neurons in sequence.
        2) There are four main ascending tracts carrying general somatic
        sensory information:
            a] Dorsal Column Pathway - conveys information about pressure,
            fine touch, and proprioception; what are termed discriminative
        senses since we can locate precisely on the body where the
    sensation occurred.
                1] Sequence of Events
                    a} Axons of sensory neurons enter into the spinal cord, at
                    the dorsal horns, and send information up the dorsal
                    white column.
                    b} These first order neurons travel up to the medulla where
                    they synapse with second order neurons.
                        1} The synaptic event occurs either at the nucleus
                        cuneatus or the nucleus gracilis.
                        2} The axons from these nuclei form the medial
                        lemniscus where the fibers decussate and ascend to
                the thalamus.
                    c} Third order neurons synapse with these axons in the
                    thalamus and travel to the primary somatosensory
                    cortex.
            b] Spinothalamic Pathway - conveys information on coarser touch,
            pain, deep pressure, and temperature: the less discriminating
        senses.
                                                65
            1] Sequence of Events
                a} Axons of sensory neurons enter the spinal cord.
                b} These first order neurons synapse with interneurons in
                the dorsal horns.
                c} These second order neurons decussate and enter into
                either the lateral or anterior spinothalamic tracts.
                d} The second order neurons then synapse with third order
                neurons in the cerebrum.
                e} The third order neurons carry the information to the
                primary somatosensory cortex.
        c] Posterior Spinocerebellar Pathways - conveys information on
    proprioception to the cerebellum.
            1] Either decussates twice or not at all.
        d] Anterior Spinocerebellar Pathways - conveys information on
        proprioception to the cerebellum.
            1] Either decussates twice or not at all.
c) Descending Pathways                                           {p. 400, f. 13.34
    1) These tracts transmit motor information from the cerebrum
    towards the effector organs.
    2) There are two classes of somatic motor tracts:
        a] Pyramidal or Corticospinal Tracts - control precise and skill
    requiring voluntary movements.
            1] The Events
                a} Pyramidal cells, in the primary motor cortex, send axons
                to the spinal cord gray matter.
                    1} They will decussate along the way.
                b} In the spinal gray matter these first order neurons
                synapse with very short interneurons.
                c} These second order neurons will then synapse with the
                spinal motor nerves in the ventral horn which will send
            axons to the effector organs.
        b] Extrapyramidal Tracts - these are all of the other motor tracts.
            1] The extrapyramidal tracts include:
                a} Tectospinal Tract - originating from the visual tectum
             (or superior colliculus) it is involved in our visual reflexes.
                b} Vestibulospinal Tract - originating from the vestibular
            nuclei.
                c} Reticulospinal Tract - originating from the reticular
                formation.
            2] The extrapyramidal tracts allow the cerebellum to
            effectively control and coordinate the body movements.




                                            66
                    CHAPTER 14: NEUROLOGY 3; THE PNS
                                      A. Introduction
1. The PNS is the nervous structures outside of the CNS
2. The PNS can be divided into:                                   {p. 410, f. 14.1}
   a) The Sensory or Afferent Division - carries sensory information
   to the CNS from the sense receptors. It can be further divided:
       1) Somatic Sensory - sensory innervation of the outer portions
       of the soma (the body). It can be subdivided into:
           a] General Somatic Senses - senses whose receptors are
           spread widely throughout the “outer” body.
               1] It receives information about pain, temperature,
               pressure, touch, vibration, and proprioception (the amount of
               stretch on muscles, joints, and tendons).
           b] Special Somatic Senses - senses whose receptors are
           concentrated in a small, specialized area.
               1] They are the senses of vision, olfaction, audition, and
               equilibrium.
       2) Visceral Sensory - sensory innervation of the inner body, the
       viscera, the heart, lungs, G.I. tract, etc. It can be subdivided:
           a] General Visceral Senses - senses whose receptors are
           widely distributed throughout inner body, the viscera.
               1] It receives information about pain, temperature,
               stretch, nausea, irritation, hunger, and chemical changes.
           b] Special Visceral Senses - senses whose receptors are
           concentrated in a small, specialized area.
               1] There is only one sense considered in this category, taste.
   b) The Motor or Efferent Division - carries motor information from the
   CNS from the sense receptors. It can be further divided:
       1) Somatic Motor - motor innervation of most of the skeletal
   muscles (excepting the pharyngeal arch muscles). It is also
   known as the Voluntary Nervous System. It can not be subdivided.
       2) Visceral Motor - motor innervation of the inner body, theviscera..
   It can be subdivided:
           a] General Visceral Motor - controls the cardiac and smooth
           muscles. It is also known as the ANS.
           b] Special Visceral Motor - it controls the pharyngeal muscles.

                          B. Peripheral Sensory Receptors
1. Peripheral sensory receptors pick up sensory stimuli and transmit
   signals up sensory axons.
   a) The various types of peripheral sensory receptors fit into two
   classes:
       1) Dendritic Endings (of sensory neurons)
           a] They monitor most types of general sensory information such
           as pain and touch.
       2) (complete cell) Receptor Cells - either small neurons or
       specialized epithelial cells which will transmit the impulse to a
       sensory neuron.
           a] They monitor most of the special senses.
                                              67
2. Peripheral sensory receptors can be classified in a number of ways:
   a) Classification Based on the Type of Stimuli Detected - the type of
   stimulus detected is used to name the receptor. Some examples are:
       1) Mechanoreceptors - respond to mechanical forces such as stretch,
       vibration, pressure, and touch.
       2) Thermoreceptors - respond to changes in temperature.
       3) Photoreceptors - respond to light.
       4) Chemoreceptors - respond to chemicals.
           a] These chemicals must be in solution to be detected.
           b] ex; taste, smell, blood pH.
       5) Nociceptors - respond to harmful stimuli involving pain.
   b) Classification Based on Location
       1) Exteroceptors - respond to stimuli outside of the body.
       2) Interoceptors - respond to stimuli inside of the body.
       3) Proprioceptors - measure the degree of stretch in skeletal
   muscles and their joints.
   c) Classification Based on Structure
       1) Special Sensory Receptors - these are complete cell receptor
       cells. We will discuss them later under “Special Senses”.
       2) General Sensory receptors - widely distributed, they take the
       form of dendritic endings. They monitor touch, pressure, stretch,
       pain, proprioception, vibration, and temperature.
           a] There are two types:                         {p. 412-13, T. 14.1}
               1] Free Dendritic Endings
                   a} They invade most of our tissues during development.
                   b} They respond to pain and temperature.
                      1} ex; Merkel discs, root hair plexus
               2] Encapsulated Dendritic Endings
                   a} They are enclosed in a c.t. capsule.
                   b} Most are mechanoreceptors. Some are:
                      1} Krause End Bulbs - monitor fine touch in the mucus
                      membranes of the eyes and mouth.
                      2} Meissner’s Corpuscles - monitor fine touch in the
                          dermal papillae of the integument.
                      3} Ruffini’s Corpuscles- monitor continuous pressure on
                      the skin. They are located in the dermis.
                      4} Pacinian Corpuscles - widely distributed throughout
                      our deep c.t.s, they monitor vibrations.
                      5} Proprioceptors - respond to stretch in the locomotory
                      muscles and their joints.
                          (a) There are three classes:
                              (1) neuromuscular spindles
                              (2) Golgi tendon organs
                              (3) joint kinesthetic receptors



                            C. Peripheral Motor Endings
1. Innervation of Skeletal Muscles                  {p. 416, f.14.5; p. 417, f. 14.6}
    a) Neuromuscular Junctions or Motor End Plates are points where a
    motor neuron innervates skeletal muscle fibers.
        1) A single NMJ is associated with each skeletal muscle cell.
                                            68
        2) Comparing the NMJ and Nerve Synapse
            a] The NMJ structurally shares many features with nerve
        synapses:
                1] A synaptic cleft separates the axon and the myofiber.
                2] The axon terminals contain synaptic vesicles which will
                release neurotransmitters when stimulated.
                    a} The neurotransmitter is acetylcholine.
                    b} This will cause an impulse to travel along the
                    sarcolemma, down the T-tubule, causing the release of
                calcium and muscle contraction.
            b] There are, however, some differences:
                1] The axon terminals lie in a depression in the sarcolemma
            called the motor plate.
                    a} The motor plate is convoluted and lined with a basal
                    lamina.
                    b} It has acetylcholine receptor proteins.
                2] On the motor plate we also have the enzyme
                acetylcholinesterase which will break down acetylcholine
            after each contraction.
        3) A Motor Unit is a motor neuron and all of the myofiberrs its
            axonal processes innervate (via NMJs).
            a] The number of muscle cells in a motor unit and the number of
                motor units in a muscle organ varies.
                1] Remember: muscle contracts at 1005 (the “all or none”
            hypothesis). The fewer the number of myofibers per unit,
            the more motor units per muscle, the more precise is the
        control over the amount of force exerted.
2. Innervation of Smooth Muscle and Glands
    a) Near the smooth muscle or gland which it innervates an axon
    terminal swells into rows of knoblike structures called Varicosities.
        1) These varicosities are presynaptic terminals filled with synaptic
    vesicles.
    b) The synaptic cleft in these innervations is of a greater width which
    may help to explain the slower response of smooth muscle compared
    to skeletal muscle.
3. Innervation of Cardiac Muscle
    a) The innervation of cardiac muscle only occurs at one point in the
    heart muscle mass (the myocardium).
        1) This place is the sinoatrial node.
        2) The structure of this point of innervation is very similar to that
        for smooth muscle.

                                C. The Cranial Nerves
1. Introduction                                                        {p. 418, f. 14.7}
    a) There are twelve pairs of cranial nerves which extend from the brain,
    through the foramen of the skull, directly into the PNS.
        1) Most innervate the head and neck.
           a] CN 10 innervates other areas as well.
        2) Most attach at the brain stem.
           a] Excepting CN 1 and 2.
2. The Twelve Pairs of Cranial Nerves                      {p. 419-26, T. 14.2}
    a) CN 1, the Olfactory Nerve - Sensory; located at the forebrain.
                                              69
   b) CN 2, the Optic Nerve -Sensory; it is actually an outgrowth of the
   forebrain.
   c) CN 3, the Oculomotor Nerve - Motor; control four of the extrinsic
   muscles of the eye.
   d) CN 4, the Trochlear Nerve - Motor; innervates one of the other
   extrinsic ocular muscles.
   e) CN 5, the Trigeminal Nerve - Both; sensory for the face and motor for
   the muscles of mastication.
   f) CN 6, the Abducens Nerve- Motor; innervates the extrinsic ocular
   muscle that abducts the eye.
   g) CN 7, the Facial Nerve - Both;sensory for proprioception and some of
   taste, motor for the muscles of facial expression and facial glands
   (i.e.; salivary, lacrimal).
   h) CN 8, the Vestibulocochlear Nerve - Sensory; hearing and equilibrium.
   i) CN 9, the Glossopharyngeal Nerve - Both; sensory for taste and
   general senses of the tongue and pharynx, motor control of tongue
   and pharynx.
   j) CN 10, the Vagus Nerve - Both; innervates various structures
   throughout the body.
   k) CN 11, the Accessory Nerve - Motor; acts as an accessory to the
   vagus in the head and neck.
   l) CN 12, the Hypoglossal Nerve - Motor; innervates muscles of the
   tongue.


                                  D. The Spinal Nerves
1. Introduction
    a) There are thirty one pairs of spinal nerves.               {p. 426, f. 14.8}
        1) They are divided into:
            a] Cervical Nerves - There are 8 pairs designated C1-C8.
            b] Thoracic Nerves - There are 12 pairs designated T1-T12.
            c] Lumbar Nerves - There are 5 pairs designated L1-L5.
            d] Sacral Nerves - There are 5 pairs designated S1-S5.
            e] Coccygeal Nerves - There is 1 pair designated C0.
        2) All spinal nerves lay inferior to the correspondingly numbered
        vertebra (ex; L5 is inferior to vertebra L5) except for the cervical
    spinal nerves.
            a] Instead the cervical spinal nerves are superior to the
            correspondingly numbered cervical vertebrae.
                1] ex; C5 is above cervical vertebra C5.
                2] This is because the first pair exit between the skull and the
                atlas.
    b) The spinal nerves innervate most of the body inferior to the head.
    c) The spinal nerve attaches to the spinal cord by a pair of roots.
{p. 427, f. 14.9}
        1) The two roots are the dorsal and ventral roots:
            a] The Dorsal Root contains sensory fibers and so carries afferent
            information towards the spinal cord.
                1] The perikarya of these sensory neurons are located in the
                Dorsal Root Ganglion.
            b] The Ventral Root contains motor fibers and so carries efferent
            information towards the effector organs.
                                                70
                1] The perikarya of these motor neurons are located in the
            ventral horns, and sometimes the lateral horns, of the
            spinal cord gray matter.
        2) The spinal nerve forms from the joining of the dorsal and ventral
   roots.
            a] So the spinal nerve carries both sensory and motor information.
            b] It passes through the intervertebral foramen as it exits the
        vertebral canal.
            c] Once it exits the intervertebral foramen it branches into the
        two rami.
                1] The Dorsal Ramus extends to the dorsum of the body trunk.
                    a} So it carries motor information to and sensory
                    information from the back.
                2] The Ventral Ramus extends to the anterior and lateral
                regions of the body trunk and to the limbs.
                    a} So it carries motor information to and sensory
                    information from the anterior body, the lateral body, and
                the limbs.
2. Specific Innervation of Body Regions
   a) The Back
        1) Each dorsal ramus will give rise to three or four branches which
   will innervate a horizontal band of skin and muscle along an orderly,
   segmental plan.
   b) The Anterior Abdominal and Thoracic Walls
        1) Only in the thorax do the ventral rami display the orderly,
   segmental pattern shown by the dorsal rami.
            a] Each ventral ramus runs along each rib as the Intercostal Nerve.
                1] The intercostal nerve innervates the intercostal muscles
            and then descends inferiorly to supply the abdominal wall.
        2) There are exceptions to this:
            a] Spinal nerve T1 sends most of its fibers into the brachial
            plexus.
            b] Spinal nerve T12 is actually subcostal, being below R12.
   c) The Cervical Plexus                                          {p. 428, f. 14.10}
        1) General Comments About Nerve Plexuses
            a] Excepting for spinal nerves T1 through T12, all spinal nerve
        ventral rami branch and these branches join at a position
        lateral to the vertebral column forming nerve plexuses.
            b] These plexuses generally service the limbs.
            c] The fibers traveling within a plexus will “criss-cross” and so:
                1] Fibers from each ventral ramus are redistributed, traveling
                to different regions of the body and traveling by different
            routes.
                2] Each terminal branch of a nerve plexus contains the fibers of
                more than one spinal nerve.
        2) The Cervical Plexus
            a] The cervical plexus is formed by the ventral rami of spinal
            nerves C1 through C4.
                1] They are located deep to the sternocleidomastoid muscle.
            b] The branches have various functions:
                1] Most are cutaneous branches.
                    a} They supply the skin of the face, neck, posterior head, and
                superiormost shoulder.
                                                71
              2] The rest are motor nerves.
                   a} They supply muscles of the anterior neck.
                       1} Especially noteworthy is the Phrenic Nerve which
                       innervates the diaphragm.
d) The Brachial Plexus                                            {p. 431, 14.11}
    1) The brachial plexus contains most of the nerves innervating the
arm.
         a] It is located in the axillary region and the neck.
    2) It is composed of the ventral rami of spinal nerves C5 through T1.
         a] These rami (called “roots”) anastomize to form three trunks:
    the upper, middle, and lower trunks.
         b] Each trunk will branch into a posterior and anterior division.
         c] The anterior and posterior division, in turn, will form the
         lateral, medial, and posterior cords.
         d] The brachial plexus ends in the axilla where it gives rise to the
    five major nerves of the arm:
              1] Axillary Nerve
              2] Musculocutaneous Nerve
              3] Median Nerve
              4] Ulnar Nerve
              5] Radial Nerve
e) The Lumbar Plexus                                              {p. 433, f. 14.12}
    1) The lumbar plexus is formed from spinal nerves L 1 through L4 and
    is located within the posterior abdominal wall.
    2) The lumbar plexus serves mainly to innervate the anterior thigh.
    3) The lumbar plexus gives rise to six nerves plus a seventh nerve,
    the lumbosacral trunk, which actually arises from both the
    lumbar and sacral plexi.
         a] The six nerves are:
              1] Iliohypogastric Nerve
              2] Ilioinguinal Nerve
              3] Genitofemoral Nerve
              4] Lateral Femoral Cutaneous Nerve
              5] Obturator Nerve - which passes through the obturator
                   foramen.
              6] Femoral Nerve - the largest of the nerves arising from the
              lumbar plexus.
                   a} It innervates all of the anterior thigh musculature.
f) The Sacral Plexus                                                     {p. 434, f. 14.13}
    1) The sacral plexus is formed from spinal nerves L 4 through S4 and
         is located caudal to the lumbar plexus.
         a] L4 is involved in both the lumbar and sacral plexuses.
              1] So it is also called the Lumbosacral Trunk.
              2] And the lumbar and sacral plexuses are often combined into
              one plexus called the Lumbosacral Plexus.
    2) The sacral plexus has twelve named branches going to the
    buttocks, lower limb, posterior thigh, perineum, and pelvis. They
         include:
         a] Superior Gluteal Nerve - innervates the gluteal region.
         b] Inferior Gluteal Nerve - innervates the gluteal region.
         c] Sciatic Nerve
              1] The sciatic nerve is actually made up of two nerves.
                   a} The two nerves are:
                                                72
                   1} Tibial Nerve - which will extend into the foot
                   becoming the plantar nerves.
                   2} Common Peroneal Nerve - which will innervate the
                   peroneal muscles and some of the muscles of the foot.
            2] Together these two nerves make the sciatic the largest
            nerve of the body being both the longest and the thickest
        nerve.
g) Joint Innervation
    1) Joint innervation has been shown to follow Hilton’s Law for the
    most part.
        a] Hilton’s Law states: “Any nerve which innervates a muscle
        producing movement at the joint innervates that joint as well
    as the skin above the joint.”
            1] Ex; The musculocutaneous, radial, median, and ulnar nerves
            innervate the elbow joint since they innervate the muscles
        producing movement at the elbow.
h) Skin Innervation                                           {p. 436, f. 14.14}
    1) A dermatome is an area of skin innervated by the cutaneous
        branches of a single spinal nerve.
        a] Dermatomes show a segmental pattern over the body, as do the
        spinal nerves.
        b] All spinal nerves are involved with dermatomes except for
        spinal nerve C1.




                                          73
                    CHAPTER 15: NEUROLOGY 4; THE ANS
                                      A. Introduction
1. The ANS, or autonomic nervous system, represents the general visceral
   sensory and general visceral motor divisions of the PNS.
   a) The ANS is a system of motor neurons which innervate the glands,
   smooth muscles, and cardiac muscle.
       1) The ANS controls the various visceral functions.
2. Structural Organization                       {p. 446, f. 15.3; p. 447, f. 15.4}
   a) The typical motor unit of the ANS consists of two neurons:
       1) Preganglionic Neuron
           a] Its cell body lies in the spinal cord or brain.
           b] It sends an axon, termed the Preganglionic Axon, into the PNS.
       2) Postganglionic Neuron
           a] Its cell body lies within an Autonomic Ganglion in the PNS.
               1] Since the autonomic ganglia contain the cell bodies of motor
               neurons they are referred to as “motor ganglia”.
                   a} The autonomic ganglia also contain short neurons called
                   Intrinsic Ganglionic Cells.
                       1} Intrinsic ganglionic cells are much like interneurons.
                       2} Intrinsic ganglionic cells regulate the actions of
                       postganglionic neurons by turning them off after they
                   have fired.
           b] It sends an axon, termed the Postganglionic Axon, to the
           effector organ.
       3) There are two divisions of the ANS:The Sympathetic and
   Parasympathetic Divisions.
           a] The two divisions often innervate the same organs but produce
           opposite reactions.


                             B. The Sympathetic Division
1. Basic Structure and Function                                   {p. 453, f. 15.7}
   a) The sympathetic division serves for “flight, fight, and fright”.
       1) The sympathetic division stimulates the body to respond to
       situations such as excitement, heavy exercise, and emergencies.
       2) At the same time, the sympathetic division inhibits processes
       such as digestion and urine production which are not required in
   an emergency.
   b) The sympathetic division arises from spinal nerves T 1 through L2,
   what is termed the Thoracolumbar Division.
       1) The cell bodies of the sympathetic division’s preganglionic
       neurons are located in the lateral horns of spinal cord gray matter.
       2) The sympathetic division supplies all of the internal visceral
       organs, superficial visceral organs (e.g.; sweat glands), and the
   walls of all blood vessels.
   c) The sympathetic division uses a variety of neurotransmitters:
       1) The neurotransmitter acetylcholine is used for communication
   between the preganglionic and postganglionc neurons.
       2) The neurotransmitters epinepherine and/or norepinepherine are
                                             74
   used for communication between the postganglionc neurons and
           the effector organs.
   d) The sympathetic division has two classes of ganglia:
       1) Chain Ganglia ( aka; Paravertebral Ganglia)
           a] The chain ganglia are paired ganglia located parallel to the
           spinal cord (anteriolateral to the vertebral column).
               1] Superior and inferior chain ganglia are connected by short
               nerves.
                   a} This forms the Sympathetic Chain or Sympathetic Trunk.
           b] There are approximately one pair of chain ganglia per pair of
           spinal nerves.
               1] Since some adjacent ganglia will fuse during embryogenesis,
           in actuality the ratio is not quite one to one.
                   a} Ex; The neck has 8 pairs of spinal nerves but only 3 pairs
                   of chain ganglia.
                   b} On average there are 22 to 24 pairs of chain ganglia:
                       1} 3 pairs of cervical chain ganglia
                       2} 11 pairs of thoracic chain ganglia.
                       3} 4 pairs of lumbar chain ganglia
                       4} 4 pairs of sacral chain ganglia
                       5} 1 pair of coccygeal chain ganglia.
       2) Prevertebral Ganglia (aka; Collateral Ganglia)
           a] The prevertebral ganglia differ from the chain ganglia in:
               1] They are not segmentally arranged
               2] they are not paired
               3] they are found only in the abdominopelvic cavity
               4] they are located anterior to the vertebral column.
           b] The prevertebral ganglia lay within the nerve plexuses for
           which they are named. Such as the:
               1] Celiac Ganglion
               2] Superior Mesenteric Ganglion
               3] Inferior Mesenteric Ganglion
               4] Inferior Hypogastric Ganglion
2. Sympathetic Pathways               {p. 455-7, f. 15.9-14}
   a) Basic Pathway Information
       1) The preganglionic axons extend through the ventral root and enter
       into the spinal nerve as the first part of the ventral ramus.
           a] Their cell bodies, of course, are located in the lateral horns of
           spinal cord gray matter.
           b] From the ventral ramus, of the spinal nerve, the axons enter
       into the nearest chain ganglion via the White Ramus
       Communicans.
               1] The white ramus communicans contains all of the
               preganglionic fibers traveling to the chain ganglia.
                   a} It is white because preganglionic fibers are myelinated.
                   b} The white ramus communicans occur only in association
                       with chain ganglia between T1 and L2 where sympathetic
               outflow occurs.
               2] From the nearest chain ganglion the preganglionic fibers can:
                   a} Synapse with a postganglionic neuron in that (the nearest)
                   chain ganglion.
                   b} Pass through that ganglion without synapsing and extend
                   out to a prevertebral ganglion where the synaptic event
                                                75
             will occur.
                  c} Pass through that chain ganglion without synapsing and
                  ascend or descend the sympathetic chain to synapse with
                  a postganglionic neuron in another chain ganglion.
        c] If synapsis does occur in a chain ganglion then the
             postganglionic neuron will extend its axons back towards the
             ventral ramus on their way to the effector organ.
             1] To get from the chain ganglion to the ventral ramus the
             axons must travel across the Gray Ramus Communicans.
                  a} The gray ramus communicans contains the postganglionic
                  fibers traveling to the peripheral body.
                      1} The gray ramus communicans occurs at all chain
                      ganglia.
                      2} The gray ramus communicans is gray since the
                      postganglionic axons are unmyelinated.
b) Pathways to the Peripheral Body - to innervate sweat glands,
arrector pili, and peripheral blood vessels.
    1) Preganglionic fibers enter the nearest chain ganglion and
immediately synapse with postganglionic neurons.
    2) The postganglionic axons travel from the sympathetic chain into
the gray ramus communicans and then into the ventral ramus.
    3) The axons travel through the ventral ramus and out to their
    effector organs.
c) Pathways to the Head - to sympathetically innervate the head.
    1) Preganglionic neurons arise from T1 through T4.
    2) They enter the nearest chain ganglion and travel up the
    sympathetic chain to the superior cervical ganglia.
    3) The preganglionic axons synapse with the postganglionic neurons
    in the superior cervical chain.
    4) The postganglionic axons exit the chain ganglion, via the gray
    ramus communicans, and extend to their effector organs of the
head.
        a] These are the glands, blood vessels, and smooth muscles of the
        head.
d) Pathways to the Thorax - to innervate the organs of the thoracic
cavity (ex; increase heart rate, increase respiration rate).
    1) Preganglionic neurons arise from T1 through T6.
    2) Some fibers will synapse in the nearest chain ganglion and the
postganglionic neurons will travel directly to the effector organ
(ex; lungs, esophagus).
    3) Other fibers (mostly those servicing the heart) enter the chain
ganglion and then ascend the sympathetic chain to synapse in a
cervical ganglion. the postganglionic fibers travel from the
cervical ganglion to the heart (or other effector organ).
e) Pathways to the Abdomen - to innervate the abdominal organs.
    1) Preganglionic fibers originate from T5 through L2.
    2} The preganglionic fibers enter the nearest chain ganglion and exit
    without synapsing. They travel as the splanchnic nerves to the
prevertebral ganglia.
    3) Synapsis occurs in the prevertebral ganglion and the
    postganglionic nerve fibers extend to the effector organ.
f) Pathways to the Pelvic Region - to innervate the pelvic organs.
    1) The preganglionic fibers originate from T 10 through L2.
                                              76
   2) The preganglionic fibers enter the nearest chain ganglion and
       travel down the sympathetic trunk to the lumbar and sacral chain
   ganglia.
       3) Some of the preganglionic fibers will synapse in the lumbar and
   sacral chain ganglia and travel to the effector organs as the
   splanchnic, lumbar, and sacral nerves.
       4) Others will pass directly to autonomic plexi and synapse in
       prevertebral ganglia in that area. The postganglionic fibers will
   then travel to the effector organs.
3. The Adrenal Medulla of the Adrenal Gland                     {p. 457 f. 15.14}
   a) The adrenal medulla is the central portion of the adrenal gland.
       1) The adrenal gland is an endocrine organ located immediately
       superior to the kidneys on the posterior abdominal wall.
       2) Both the adrenal medulla and the adrenal cortex are considered to
       be endocrine organs.
           a] Although they are portions of the same organ, in many ways
       they are two dissimilar organs.
                1] The adrenal cortex is purely endocrine and of mesodermal
                origin.
                2] The adrenal medulla is also an endocrine structure but its
           secretions mimic the postganglionic neurotransmitters of
       the sympathetic division.
                    a} It produces epinepherine and norepinepherine.
                    b} It derives from the embryonic germ layer the ectoderm.
   b) In many ways, then, the adrenal medulla can be considered as a very
   specialized sympathetic ganglion.
       1) It is composed of supporting cells postganglionic neurons which
   lack processes.
           a] Instead of innervating an effector organ, they secrete their
       neurotransmitter into the blood stream producing a wide range
       of excitatory responses.
           b] The postganglionic neurons are stimulated to release their
                products by preganglionic neurons arising T 6 through T11.


                          C The Parasympathetic Division
1. The parasympathetic division stimulates the body to relax.
{p. 449, f. 15.5}
    a) It allows the body to conserve energy and to perform basic
    maintenance functions such as digestion and excretion.
    b) It innervates most of the same effector organs as does the
    sympathetic division but it ellicts opposite behaviors.
         1) This is because its postganglionic neurons (and preganglionic
         neurons for that matter) use the neurotransmitter acetylcholine.
         2) The sympathetic and parasympathetic divisions balance each
         other out when one is not needed over the other.
2) The parasympathetic division arises from both the head and sacral
    spinal cord, from what is termed the Craniosacral Division.
    a) The cell bodies of its preganglionic neurons are located in the CNS.
         1) Their axons are myelinated and quite long since parasympathetic
         ganglia are located very close to or on the effector organs.
             a] The postganglionic axons are unmyelinated and relatively
                                               77
           shorter.
   b) The cranial portion of the parasympathetic division innervates the
   head, neck, thorax, and much of the abdominopelvic cavity.
       1) The preganglionic fibers will run with some of the cranial nerves:
           a] Oculomotor Nerve (CN 3) - innervates the smooth muscles of
           the eye causing the pupil to constrict and the eye to bulge.
           b] Facial Nerve (CN 7) - innervate the glands of the head and
           stimulates their secretion.
               1] i.e.; certain of the salivary glands and the lacrimal glands
               2] Synapse occurs in either the submandibular ganglion or the
               sphenopalatine ganglion.
           c] Glossopharyngeal Nerve (CN 9) - stimulates the secretion of the
           parotid gland.
               1] Synapse occurs in the otic ganglion.
           d] Vagus Nerve (CN 10) - innervates many organs in the thoracic,
           abdominal, and pelvic regions.
               1] It is involved with many plexuses (ex; cardiac plexus)
               2] For example it slows the heart and respiratory rates.
   c) The sacral portion innervates most of the organs of the pelvis.
       1) ex; stimulates urination, defecation
       2) These preganglionic neurons arise from spinal nerves S 1 through S4.
           a] The preganglionic neurons lay in the visceral motor region of
       the spinal cord gray matter.
           b] Pathway:
               1] The preganglionic fibers travel through the ventral rami.
               2] In the ventral rami they branchinto the Pelvic Splanchnic
           Nerves.
               3] These branches run into the Inferior Hypogastric Plexus
               (aka; Pelvic Plexus).
               4] There some will synapse with ganglia in the inferior
               hypogastric plexus.
               5] Others synapse in ganglia located on the effector organ.



                          D. Central Control off the ANS
1. There are several levels of involuntary control over the ANS:
   a) Control by the brain stem and spinal cord:
       1) Direct influence over the ANS is held in the reticular formation
   of the brain stem.
           a] Centers in the medulla oblongata monitor and regulate heart
       rate, breathing rate, digestive activity, etc.
           b] The pons also exerts some control over the ANS in coordination
           with the medulla.
       2) Control of the ANS by the spinal cord is achieved through the
       spinal visceral reflexes.
   b) Control by the hypothalamus:
       1) The hypothalamus serves as the integration center of the ANS.
           a] The medial and anterior portions control parasympathetic
           activity.
           b] The lateral and posterior portions control sympathetic activity.
   c) Control by the cerebral cortex:
                                              78
      10 Some have been able to learn how to consciously control aspects
      of the ANS through use of the cerebral cortex.

                  E. Visceral Sensory Neurons: An Overview
1. The visceral PNS contains sensory neurons as well as motor neurons.
   a) They are part of the General Visceral Sensory Division and monitor
   such as stretch, temperature, and irritation within the visceral
   organs
       1) They are unencapsulated dendritic endings.
   b) The cell bodies of these neurons are located in the dorsal root
   ganglia and in the sensory ganglia of the cranial nerves.
       1) Their axons often travel with the axons of parasympathetic and
   sympathetic neurons (but in the opposite direction).




                                          79
           CHAPTER 16: NEUROLOGY 5; THE SPECIAL SENSES
                                      A. Introduction
1. The special senses are: smell, taste, sight, hearing, and equilibrium.
2.The special senses, like the general senses, allow us to detect
   changes in our environment.
   a) The recepror organs of the special sense, however, are much more
   complex.
       1) Olfaction is the least specialized while vision is the most.
       2) Special senses use complete cell receptor cells.


                                       B. Olfaction
1. Olfaction, like gustation, is considered to be a chemical sense since it
   responds to chemical stimuli.
   a) Being a chemoreceptor it requires that the chemicals be in solution
   for detection.
2. The receptors for olfaction are located in the nasal epithelium in the
   superior portion of the nasal cavity.                         {p. 469, f. 16.3}
   a) This portion of the nasal mucosa is called the Olfactory Mucosa. It
   consists of two cell types:
       1) Supporting Cells - these are tall, ciliated, columnar epithelial
       cells that surround the second cell type..
           a] They produce mucus which helps in olfaction by keeping the
           chemicals in solution.
       2) Olfactory Cells/Olfactory Receptor Cells - these are bipolar
       neurons whose cell bodies are located amid the supporting cells.
           a] The distal end of each receptor cell contains 6 to 8 dendritic
       processes termed Olfactory Hairs.
               1] These olfactory hairs spread out amid the cilia of the
               supporting cells to pick up chemical stimuli.
           b] The axons of the olfactory cells unite to form the Olfactory
           Nerves.
               1] These axons are unmyelinated.
               2] The olfactory nerves pass through the olfactory foramina of
               the cribriform plate and synapse in the Olfactory Bulbs with
           the Mitral Cells.
                          a} The mitral cell axons form CN 1, the Olfactory
                          Nerve.


                                      C. Gustatation
1. The gustatory (or Taste) receptors are located in the mouth and portions
   of the pharynx in structures called Taste Buds.              {p. 467, f. 16.1}
   a) Most taste buds are located on the tongue but some are located on the
   soft palate and in the upper throat.
   b) Taste buds are oval structures made up of two cell types:
       1) Supporting Cells - these are columnar epithelial cells which
       surround and protect the second cell type.
                                            80
       2) Gustatory Cells - these are neuroepithelial cells which respond to
       chemical stimuli.
           a] Between 4 to 20 receptor cells are located in each taste bud.
   c) Each taste bud is embedded within the mucus membrane of the mouth.
       1) It will have an opening to the surface of the mucus membrane
       called a Taste Pore.
           a] Hair-like structures called Gustatory Hairs pass through the
       taste pore onto the external surface so as to pick up stimuli.
               1] They are actually specialized stereocilia.
       2) The taste buds of the tongue are located in elevations of the
       mucosa called Papillae.
           a] Typically they are located at the bases of these elevations
           where they are better protected.
           b] There are several types:
               1] Circumvallate/Vallate Papillae - the largest type, these are
               large, circular papillae found in a single, V-shaped row at the
               back of the tongue.
               2] Fungiform Papillae - “mushroom-shaped” papillae located
           on the tip and sides of the tongue.
               3] Foliate Papillae - “leaf-shaped” papillae located on the
               sides of the tongue.
               4] Filiform Papillae - pointed, hair-like papillae located on the
               anterior two thirds of the tongue.
2. As is the case with olfaction, gustation requires the chemicals to be in
   solution for detection. This is handled by saliva.
   a) The stimulus is detected by the gustatory hairs.
       1) There are only four true tastes: sweet, sour, bitter, and salty.
           a] All other “tastes” are due to an interaction between taste and
       smell.
           b] Certain regions of the tongue are more sensitive to one taste
       than to another.
   b) This causes an impulse to be passed through the gustatory receptor
       cell to a sensory neuron.
       1) ensory neurons will have their dendritic processes at the bases
       of taste buds in contact with the gustatory receptor cells.
       2) The taste buds receive cranial nerve innervation:
           a] The anterior two thirds of the tongue is supplied by CN 7, the
       Facial.
           b] The posterior third of the tongue is supplied by CN 9, the
           Glossopharyngeal.
           c] The epiglottis is supplies by CN 10, the Vagus.
   c) The impulse is conveyed through the medulla oblongata and thalamus
   to the gustatory center of the cerebral cortex.


                                         D. Vision
1.Accessory Structures of the Eye                                        {p. 472, f. 16.5}
   a) Eyebrows
       1) The skin of the eyebrow is richly supplied with sebaceous glands
       and have protective hairs.
           a] The hairs of the eyebrow help to protect the eyebrow from
           falling objects, perspiration, and the direct rays of the sun.
                                              81
b) Eyelids or Palpebrae
    1) Functions:
        a] shade eyes from excessive light
        b] protect the eyes when sleeping
        c] protect the eyes from foreign objects
        d] distribute lubricating secretions over the eyeballs.
    2) Features of the Palpebrae:
        a] The upper eyelid is termed the Superior Palpebra.
        b] The lower eyelid is termed the Inferior Palpebra.
        c] The space between the palpebrae is termed the Palpebral
        Fissure.
        d] The angles of the palpebral fissure (i.e.; the corners of the
        eyes) are termed the Lateral Canthus and Medial Canthus.
            1] In the medial canthus is the Lacrimal Carbuncle containing
                  sebaceous and sudoriferous glands which collect into the
            medial canthus.
        e] The more mobile superior palpebra is moved by the Levator
        Palpebra Superioris muscle.
    3) Anatomy of the Palpebrae
        a] The superficialmost layer is the epidermis.
        b] Below the epidermis is the dermis.
        c] Beneath the dermis is a subcutaneous layer of areolar c.t.
        d] Deep to the areolar c.t. are the fibers of the Orbicularis Oculi
    muscle.
        e] Then we find the Tarsal Plate.
            1] The tarsal plate is a thick fold of c.t. forming much of the
        inner wall of each palpebra.
            2] It gives form and support to each eyelid.
            3] It contains the Meibomain Glands also known as the Tarsal
            Glands.
                  a} These are modified sebaceous glands whose secretions
                  prevent the two palpebrae from adhering to one another.
        f] Beneath the tarsal plate we find the Conjunctiva.
            1] The conjunctiva is a thin mucus membrane.
            2] It has two portions:
                  a} Palpebral Conjunctiva - lines the inner aspect of the
                  palpebrae.
                  b} Bulbar or Ocular Conjunctiva - which is a reflection of
                  the conjunctiva onto the eyeball to the periphery of the
            cornea.
c). Eyelashes
    1) The eyelashes of the superior palpebra are longer than are those
    of the inferior palpebra.
    2) Eyelashes help to protect the eye from particulate matter.
    3) At the base of each eyelash follicle is a gland which secretes a
    lubricant for the eyelashes. These glands are the Glands of Zeis.
d) The Lacrimal Apparatus - The structures of the lacrimal apparatus
serve to manufacture, to distribute, and to drain the tears.
    1) The Lacrimal Gland
        a] It is about the size of an almond and produces lacrimal fluid.
            1] Lacrimal fluid (aka; tears) serves to lubricate the eye and to
        help remove particulate matter.
        b] It is located at the superior lateral portion of the orbit.
                                             82
       2) The Excretory Lacrimal Ducts
           a] There are between 6 to 12 of these ducts which carry lacrimal
           fluid from the lacrimal glands to the surface of the conjunctiva
       of the superior palpebra.
       3) The Puncta Lacrimalia/ Lacrimal Punctum
           a] These are two small pores on each medial canthus which
           collect the lacrimal fluid and drain it into the lacrimal canals.
       4) The Lacrimal Canals
           a] These are two small canals in each medial canthus, one
           draining each lacrimal punctum, which carry the lacrimal fluid
       into the lacrimal sac.
       5) The Lacrimal Sacs
           a] The two lacrimal sacs are located in the lacrimal sulci of the
       lacrimal bones.
           b] They receive lacrimal fluid from the lacrimal canals and pass
       it on to the nasolacrimal duct.
       6) The Nasolacrimal Duct
           a] The nasolacrimal duct passes through the nasolacrimal canal
           into the posterior nasal cavity.
           b] It carries lacrimal fluid into the posterior nasal cavity.
       7) The Lacrimal Fluid
           a] Lacrimal fluid is an aqueous solution used to lubricate the eye.
               1] It contains salts, some mucous, and lysozyme (a bacteria
           destroying enzyme).
           b] Lacrimal fluid is spread over the eye by the blinking of the
           palpebrae.
   e) The Extrinsic Ocular Muscles - these are skeletal muscles which
   originate outside of the eye and serve to move the eye.{
       p. 473, f. 16.6}
       1) The Rectus Muscles:
           a] Inferior Rectus - It attaches to the inferior eyeball.
               1] It depresses the eye.
           b] Superior Rectus - It attaches to the superior eyeball.
               1] It elevates the eye.
           c] Medial Rectus - It attaches to the medial eyeball.
               1] It turns the eye medially.
           d] Lateral Rectus - It attaches to the lateral eyeball.
               1] It turns the eye laterally.
       2) The Oblique Muscles:
           a] Superior Oblique - It attaches to the superior eyeball.
               1] It turns the eye laterally and depresses it inferiorly.
           b] Inferior Oblique - It attaches to the inferior eyeball.
               1] It turns the eye medially and elevates it.
2. The Eyeball, Structure and Function                             {p. 474, f. 16.7}
   a) Introduction
       1) The adult eyeball is 2.5 cm in diameter.
       2) The eyeball can be divided into three layers or tunics: the fibrous
       tunic, the vascular tunic, and the nervous tunic.


   b) The Three Tunics of the Eye
       1) The Fibrous Tunic
           a] The fibrous tunic is superficialmost layer of the eyeball.
                                              83
    b] It is composed of a tough, fibrous connective tissue.
    c] The fibrous tunic can be divided into two portions:
        1] The Sclera which makes up the posterior four fifths of the
    fibrous tunic.
             a} It is an opaque, white layer.
             b} The sclera gives shape to the eyeball, protects the
             eyeball, and serves as the point of attachment of the
        extrinsic ocular muscles.
        2] The Cornea which makes up the anterior fifth of the fibrous
        tunic.
             a} The cornea is transparent so as to allow light to enter
        the eyeball.
             b} The cornea can be described as an avascular fibrous coat
             found anterior to all other structures of the eyeball.
    d] Between the sclera and cornea is a venous sinus called the
    Canal of Schlemm.
2) The Vascular Tunic
    a] The vascular tunic is also known as the Uvea.
        1] It is overall a well vascularized and heavily pigmented
        tunic.
    b] The uvea can be divided into three portions:
        1] The Choroid which makes up about the posterior four fifths
        of the uvea.
             a} It is a thin darkly pigmented and well vascularized tissue
             lining most of the sclera.
                 1} The blood vessels of the choroid service the retina.
             b} The choroid serves to absorb light which has passed
             through the nervous tunic.
                 1} This prevents the light from being reflected back and
                 distorting the image.
        2] The Ciliary Body is a portion of the anterior uvea.
             a} It contains the ciliary muscles which will alter the shape
        of the lens to allow for accommodation.
        3] The Iris is a structure of variable pigmentation which
        surrounds the pupil.
             a} The pupil is really a circular opening in the iris.
             b} It serves to regulate the amount of light passing through
                 the pupil.
                 1} It has both radially and circularly arranged smooth
             muscles which serve to constrict and to dilate the pupil
             respectively.
             b} The iris is connected to the ciliary body.
3) The Nervous Tunic                                          {p. 477, f. 16.10}
    a] The nervous tunic is found in the posterior eye lining the
    choroid.
    b] It has two portions:
        1] The Pigmented Epithelium a layer of heavily pigmented
        columnar epithelial cells laying against the choroid.
             a} It is considered to be a portion of the choroid by some.
        2] The Retina is the true nervous tunic.
             a} It is actually an outgrowth of the brain.
                 1} As a result, its hold on the eyeball is tenuous being
             only at the optic disc and the ora serrata.
                                          84
                 b} The retina serve for image formation.
                     1} The rest of the eye is basically designed to direct
                     light, and to control the amount of light, at the retina.
                 c} The retina has a three layered arrangement, what is
                 called the “trilaminar arrangement”.
                     1} The Photoreceptor Layer - the last layer to receive
                 light and the layer in contact with the pigmented
                 epithelium.
                         (a) It is made up of neuroepithelial cells called
                         Photoreceptors which respond to light, conducting
                     an impulse towards the brain.
                              (1) There are two types of photoreceptors:
                                   [a] Rods - cylindrical in shape, respond to lower
                                   levels of light, allow for black and white vision.
                                   [b] Cones - conical in shape, need high levels of
                                   light for stimulation, allow for color vision.
                     2} The Bipolar Cell Layer - the middle layer.
                         (a) It contains a variety of cells but gets its name
                         from the Bipolar Cells.
                              (1) Bipolar cells are sensory neurons which pick up
                              the impulse from the photoreceptors and
                              conduct it towards the brain.
                     3} Ganglion Cell Layer - the first layer to receive light
                     and the furthest from the uvea.
                         (a) It contains large neurons called ganglion Cells
                         which carry the impulse form the bipolar cells
                         towards the brain.
                              (1) Their axons form CN 2, the optic nerve, and exit
                              the eyeball at the optic disc.
                                   [a] This gives us a blind spot in the eyeball.
                 d} On the retina is a conical depression filled with the cone
                 photoreceptor called the Fovea or Area Centralis.
                     1} Light is focused onto the fovea by the lens.
                     2} this is the area of highest visual acuity on the retina.
c) Other Structures of the Eyeball
    1) The Lens
        a] The lens is a complex structure composed of many layers of
    protein fibers.
        b] It serves to receive light and to focus it onto the retina.
        c] It is held in place by the Suspensory Ligaments which attach to
        the ciliary body (which, again, allows for accommodation).
2) The Cavities of the Eye
    a] The Anterior Segment - this is the space anterior to the lens.
        1] It is divided by the iris into two subsections:
             a} Anterior Chamber - the portion of the anterior segment
             between the cornea and the iris.
             b} Posterior Chamber - the portion of the anterior segment
        between the iris and the lens.
        2]The anterior segment contains Aqueous Humor a plasma filtrate.
    b] The Posterior Segment - this is the space posterior to the lens.
        1] It is much larger than is the anterior segment.
        2] It contains an extremely fluid-like connective tissue called
        Vitreous Humor .
                                                 85
               a} It helps to hold the retina in place and helps the ye to
               withstand pressure.
3. The Transmission of the Visual Impulse to the Brain
   a) Afferent Pathways to the Brain
       1) Light stimulates the rods and cones.
       2) This then creates impulses which are picked up by the bipolar
       cells.
       3) the bipolar cells send the impulse to the ganglion cells.
       4) The axons of the ganglion cells form the optic nerve.
       5) The two optic nerves cross at a pint anterior to the pituitary
       gland called the Optic Chiasma.
           a] There some of the axons cross (contralateral) and some
           continue on without crossing (ipsilateral).
       6) Most of the optic nerves’ axons will enter into the thalamus
           where they will synapse with second order neurons.
           a] The second order neurons will carry the impulse to the visual
       cortex.
   b) The Visual Field
       1) The visual field is divided into two regions for each eye:
           a] The Nasal or Medial Region.
           b] The Temporal or Lateral Region.
       2) Light patterns:
           a] Light reflecting off of an object in our medial field will strike
       the retina on the lateral region.
           b] Light reflecting off of an object in our lateral field will strike
       the retina on the medial region.
       3) Decussation or the lack of decussation:
           a] At the optic chiasma fibers from the nasal region will decussate
           before continuing on to the brain.
           b] At the optic chiasma fibers from the temporal region will
           not decussate before continuing on to the brain.


                              E. Audition and Equilibrium
1. The ear actually is responsible for the detection of three special
   senses: audition, static equilibrium, and dynamic equilibrium.
   a) The structures which detect these senses are all microscopic and are
   all located in the inner ear.
        1) The other two portions of the ear, the outer ear and middle ear,
   serve to assist the hearing portion of the inner ear but play no role
   in the equilibrium detecting portions of the inner ear.
   b) All three senses are carried to the brain by CN 8, the vestibulocochlear
   nerve.
2. The Anatomy and Divisions of the Ear                          {p. 487, f. 16.17}
   a) The External Ear (or Outer Ear)
        1) The external ear is designed to collect sounds and to direct them
            inward.
            a] The external ear consists of the: pinna, external auditory canal,
        and tympanic membrane.
        2) The Pinna (or Auricle)
            a] The pinna is composed mostly of elastic cartilage covered by
        thick skin.
                                              86
        b ]It serves to capture and to concentrate sound waves.
        c] Features of the Pinna
            1] The pinna has a rim called the Helix.
            2] The ear lobe of the pinna is termed the Lobe or Lobule.
        d] The pinna is attached to the head by ligaments and muscles.
    3) The External Auditory Canal/Meatus
        a] The external auditory canal is located within the petrous
        portion of the temporal bone.
        b] It is a tube leading from the pinna to the tympanic membrane.
            1] The walls of this tube are composed of bone lined by elastic
            cartilage extending from the pinna.
                 a} The elastic cartilage, in turn, is covered by thin, very
                 sensitive skin.
        c] At the opening of the external auditory canal the skin contains
        ceruminous glands and a few hair follicles which serve to
    protect the ear from foreign invaders.
    4) The Tympanic Membrane
        a] The tympanic membrane is a thin, semitransparent membrane
        composed of fibrous connective tissue located between the
    external auditory canal and the middle ear.
            1] The external surface is covered by skin and is concave in
                 shape.
            2] The inner surface is covered by a mucus membrane and is
            convex in shape.
b) The Middle Ear or Tympanic Cavity
    1) The middle ear is a small, epithelium lined, air filled cavity
    located within the petrous portion of the temporal bone.
        a] It is separated from the external ear by the tympanic
    membrane.
        b] It is separated from the inner ear by a thin, bony partition
        containing two openings: the Round Window and the Oval
        Window.
        c] The anterior wall of the middle ear contains an opening which
            leads into the Eustachian Tube (aka. auditory tube).
            1] The eustachian tube connects the middle ear to the pharynx
            and helps to equalize air pressure in the head.
    2) The tympanic membrane contains three small bones called the
    Auditory Ossicles.                            {p. 489, f. 16.19}
        a] The three ossicles are sequentially arranged from the tympanic
        membrane to the oval window (aka; fenestra vestibuli):
        Malleus, Incus, and Stapes.
            1] They are connected by synovial joints.
            2] They are held in place by six ligaments: anterior ligament of
            the malleus, superior ligament of the malleus, lateral
        ligament of the malleus, posterior ligament of the incus,
    superior ligament of the incus, and the annular ligament
        which attaches to the base of the stapes.
        b] There are some muscles associated with the ossicles:
            1] The Tensor Tympani Muscle - increase tension on the
            tympanic membrane by pulling the malleus medially.
                 a} It prevents damage to the inner ear due to loud sounds.
            2] The Stapedius Muscle - draws the stapes posteriorly,
            against the annular ligament, to also protect the inner ear
                                             87
        from loud sounds.
                a} It is the smallest skeletal muscle of the body.
    3) Directly below the oval window is the round window (aka;
    fenestra cochlea).
        a] Both windows separate the middle and inner ear.
        b] The round window is enclosed by a membrane called “the
        second tympanic membrane”.
c) The Inner Ear (or Internal Ear)                                    {p. 490, f. 16.20}
    1) The inner ear is a series of canals called labyrinths.
        a] There are two major divisions:
            1] Bony Labyrinth - a series of cavities in the petrous portion
        of the temporal bone.
                a} It is divided into: vestibule, cochlea, and semicircular
                canals.
                b} The bony labyrinth is lined by the periosteum.
                c} The bony labyrinth contains a fluid called Perilymph.
            2] Membranous Labyrinth - a series of sacs and tubes located
            within the bony labyrinth.
                a} In most areas it has the same general shape as the bony
                labyrinth surrounding it.
                b} The membranous labyrinth is lined by epithelium.
                c} It contains a fluid called Endolymph.
    2) The Vestibule
        a] The vestibule is an oval, central portion of the bony labyrinth.
        b] The membranous labyrinth within it consists of two
        interconnected sac like structures called the Utricle and
    Saccule.
    3) The Semicircular Canals
        a] There are three semicircular canals of the bony labyrinth.
            1] They are arranged at right angles to each other superior and
            posterior to the vestibule.
            2] The three canals are named based upon their relative
            positions: Posterior, Superior, and Lateral.
        b] The membranous labyrinth within the semicircular canals is
        called the Semicircular Ducts or Membranous Semicircular
        Canals.
            1] They communicate with one another and with the utricle and
        saccule.
            2] The membranous semicircular canals each swell at one end
            to form the Ampulla.
    4) The Cochlea (“snail shell”          )                          {p. 493, f. 16.23}
        a] The cochlea is a spiral shaped portion of the bony labyrinth
        located anterior to the vestibule.
        b] Internally, the cochlea is divided into three canals:
            Scala Vestibuli, Scala Tympani, and between them Scala
            Media.
            1] The scala media is also called the Cochlear Duct and houses
            the sensory structure responsible for hearing.
                a} It is separated from the scala vestibuli by the Vestibular
            Membrane.
                b} It is separated from the scala tympani by the Basilar
                Membrane.
        c] In the cochlear duct, on the basilar membrane, is the Organ of
                                             88
               Corti (aka; Spiral Organ), the organ of hearing.
               1] The organ of Corti consists of a series of epithelial cells
               located on the inner surface of the basilar membrane.
                    a} One of the two classes of epithelial cells is the
                    supporting cells.
                    b} The other class is the neuroepithelial Hair Cells (or
                    auditory receptor cells).
                       1} There are two types: Outer and Inner Hair Cells.
                       2} They have long stereocilia, called “hairs”, which
                       extend into an acellular membranous structure called
                    the Tectorial Membrane.
                       3} The basal ends of the hair cells are in contact with the
                    cochlear branch of CN 8.
3. The Mechanism of Hearing
   a) Sound waves reach the ear and are directed by the pinna into the
   external auditory canal.
   b) The sound waves strike the tympanic membrane causing it to vibrate.
   c) As the tympanic membrane vibrates, so to does the ossicles. The
   vibration is passed from the tympanic membrane to the malleous to
   the incus to the stapes.
   d) As the stapes vibrates it pushes the oval window in and out.
   e) This movement of the oval window sets up waves in the perilymph of
   the scala vestibule which are propagated through the scala vestibuli
   and into the fluid of the scala tympani.
   f) These waves push the vestibular membrane inwards which will
   increase pressure on the endolymph of the cochlear duct.
   g) The basilar membrane gives under this pressure and will bulge into
   the scala tympani.
   h) This sudden increase in pressure on the scala tympani pushes the
   perilymph toward the round window which is pushed back into the
   middle ear.
   i) The basilar membrane vibrates stimulating the hair cells which
   converts sound waves to sensory impulses.
       1) This is done by the movement of the basilar membrane pushing the
   stereocilia of the hair cells into the tectorial membrane.
           a] The stereocilia will become bent which will cause an impulse
           to travel from the neuroepithelial cells.
   j) These impulses are passed on to the cochlear branch of the
   vestibulocochlear nerve and then to the cortex.
4. The Mechanism of Equilibrium
   a) Equilibrium is balance. There are two types:
       1) Static equilibrium - orientation of the body (especially the head)
   relative to the ground/gravity.
           a] It is handled by sensory structures in the vestibule.
       2) Dynamic Equilibrium - the maintenance of the body’s position
       (especially the head) in response to sudden movements of the
   body.
           a] It is handled by sensory structures in the semicircular canals.
   b) Mechanism of Static Equilibriumt                             {p. 491, f. 16.21}
       1) The receptors of static equilibrium are located in the utricle and
       saccule of the vestibular portion off the bony labyrinth.
           a] They provide sensory information regarding the orientation of
       the head in space and, as a result, help us to maintain posture.
                                               89
     2) The receptors are located in the macula (meaning “spot”) on the
     wall of the utricle and saccule.
         a] Microscopically the two macula are structurally similar to the
     organ of Corti.
             1] They consist of two classes of epitheilial cells: Supporting
             Cells and Hair Cells.
                  a} The hair cells (aka; receptor cells) have long stereocilia
                  which extend into an overlying acellular membrane.
                      1} This membrane is called the Otolith Membrane.
                  b} The supporting cells are the typical columnar epithelial
                  cells.
                      1} They secrete the otolith membrane which is a
                      gelatinous glycoprotein containing calcium carbonate
                  crystals called Otoliths.
     3) The otoliths move due to movements of the head.
         a] Their extra mass is more susceptible to gravitational forces.
         b] As the otoliths move, their mass moves the otolith membrane.
         c] The membrane will then press down on the stereocilia
     triggering a nerve impulse.
         d] The impulse is transmitted along the vestibular branch of CN 8
         to the cerebral cortex.
c) Mechanism of Dynamic Equilibrium                                    {p. 492, f. 16.22}
     1) The receptors of dynamic equilibrium are located in the ampulla
of the semicircular canal portion off the bony labyrinth.
         a] They provide sensory information regarding the orientation of
     the head in space when we are moving.
     2) The three semicircular ducts in the semicircular canals are
     positioned at right angles to one another allowing for the
detection of dynamic equilibrium along three planes.
         a] The frontal plane is handled by the superior semicircular canal.
         b] The sagittal plane is handled by the posterior semicircular
         canal.
         c] The transverse/lateral plane is handled by the lateral
         semicircular canal.
     3) Within each ampulla is the sensory organ for dynamic equilibrium.
It is called the Crista Ampullaris.
         a] Microscopically the three cristae resemble the organ of Corti.
             1] It has two classes of epithelial cells: Supporting Cells and
         Hair/Receptor Cells.
             2]The hair cells have long stereocilia embedded in an acellular,
         gelatinous membrane called the cupola.
     4) When the head moves, the endolymph flows in the semicircular
ducts.
         a] It will push against the cupola which in turn presses against
         the stereocilia of the hair cells.
         b] The bending of the stereocilia will stimulate and impulse to
         travel to the vestibular branch of CN 8 and to the cortex.




                                           90
                 CHAPTER 17: CIRCULATION 1; THE BLOOD
                        A. Physical Characteristics of Blood
1.Basic Features
   a) Blood is a viscous fluid being between 4.5 and 5.5 times more viscous
   than is water.
   b) Blood has a pH of between 7.35 and 7.45.
   c) Blood has a salt concentration of 0.85 to 0.90%.
   d) Blood constitutes 8% of the body’s total weight.
2. Basic Functions - blood’s functions can be divided up into transportation,
   regulation, and protection.
   a) Transport of oxygen and carbon dioxide.
   b) transport of nutrients.
   c) transport of wastes.
   d) transport of hormones.
   e) Regulation of the body’s pH through buffers and amino acids.
   f) Regulation of body temperature.
   g) Regulation of water content in cells.
   h) Protects against toxins and foreign invaders.
   i) Protects us from excessive fluid loss.


                             B. The Components of Blood
1.Formed Elements                                                 {p. 511, T. 17.1}
   a) Formed elements are the cellular component of blood. They are:
       1) Erythrocytes - the red blood cells
       2) Leucocytes - the white blood cells. There are two classes:
           a] Granular Leucocytes - neutrophils, eosinophils, and basophils
           b] Agranular Leucocytes - lymphocytes and monocytes
       3) Thrombocytes - the platelets
   b) The formed elements are produced by the process of Hemopoiesis
   (also called Hematopoiesis).
       1) During embryonic and fetal development there are several centers
       of hemopoiesis: yolk sac, liver, spleen, thymus, lymph nodes, and
   bone marrow.
       2) In the adult hemopoiesis is less widely distributed occurring only
   in the red marrow.
           a] In the adult, all formed elements originate in the red marrow of
       bones such as the sternum, vertebrae, ribs and pelvis.
               1] However, the agranulocytes will migrate out of the red
               marrow and mature elsewhere in the lymphoid tissues such as
           the thymus, lymph nodes, and tonsils.
               2] As a result red marrow is termed Myeloid Tissue.
       3) The undifferentiated stem cells of the red marrow will develop
   into the Hemocytoblasts, multipotent cells which will give rise
   five stem cells producing all of the formed elements.
           {p. 514, f. 17.9}
           a] Megakaryoblasts - give rise to the thrombocytes.
           b] Proerythroblasts/Rubriblasts - give rise to the erythrocytes.
           c] Myeloblasts - give rise to all of the granular leucocytes
                                               91
       (neutrophils, eosinophils, and basophils).
           d] Monoblasts - give rise to the agranular leucocyte the monocyte.
           e] Lymphoblasts - give rise to the agranular leucocyte the
           lymphocyte.
NB: The first four lineages all arise from an intermediate cell type called the Myeloid
Stem Cell.
   b) Erythrocytes                                                 {p. 506, f. 17.3}
       1) Erythrocytes are highly modified cells.
           a] they are biconcave discs.
           b] They lack a nucleus.
           c] They contain the pigment Hemoglobin.
               1] Hemoglobin is a complex, globular protein which allows for
               the transport of oxygen and carbon dioxide in the blood.
               2] The hemoglobin molecule consists of a globular protein
               called Globulin and an iron containing pigment called Heme.
                    a} The heme has four iron atoms, each of which can bind to
                    one oxygen or one carbon dioxide molecule.
                        1} It carries oxygen from the lungs to the tissues of the
                        body.
                        2} It carries some carbon dioxide from the tissues of the
                        body to the lungs for elimination.
                        3} The exchange of gases is due to diffusion.
       2) Due to the lack of a nucleus, coupled with a fragile cell membrane,
       erythrocytes are short lived cells. lasting approximately 120 days.
           a] So the body must continually replace lost RBCs (at a normal
       rate of 2 million/second).
           b] Erythropoiesis is the process by which erythrocytes are
           produced. Steps:
               1] Hemocytoblasts differentiate into Proerythroblasts (or
               Rubriblasts).
               2] Proerythroblasts will then differentiate into Intermediate
           Erythroblasts (or Rubricytes).
                    a} The intermediate erythroblasts begin to synthesize
                    hemoglobin.
               3] Intermediate erythroblasts become Late Erythrocytes (or
               Metarubricytes).
                    a} In the late erythroblasts hemoglobin synthesis is at its
               maximum rate.
               4] Late erythroblasts will develop into Normoblasts.
               5] The normoblasts will lose their nuclei becoming
               Reticulocytes.
               6] The reticulocyte will mature into the Erythrocyte and enter
           into circulation.
           c] Normally the rate of erythropoiesis is equivalent to the rate of
       erythrocyte destruction.
               1] If erythropoiesis must be increased the body releases a
               hormone called Erythropoietin which stimulates increased
           erythropoiesis.
   c) Leucocytes                                                          {p. 507, f. 17.4}
       1) There are a variety of leucocytes and each has been modified to
   serve a different role in the defense of the body.
           a] Unlike the other two classes of formed elements, leucocytes
       are “complete cells” containing a nucleus when mature.
                                                92
    b] Leucocytes are broadly divided into two subclasses based on
    histological appearance:
        1] Granulocytes/Granular Leucocytes - have a lobulated nucleus
    and prominent cytoplasmic granules.
            a} They develop and mature in the red marrow.
            b} The granulocytes are: neutrophils, eosinophils, and
            basophils
        2] Agranulocytes/Agranular Leucocytes - have a spherical
        nucleus and lack prominent cytoplasmic granules.
            a} They develop in red marrow but migrate to the lymphoid
            tissues to mature.
            b} The agranulocytes are: lymphocytes and monocytes.
2) The Functional Role of Leucocytes
    a] Leucocytes defend the body from foreign invaders, fight
    infection, and play a role in inflammation.
        1] To serve in this capacity some leucocytes are:
            a} phagocytic
            b} able to secrete chemicals to counteract irritants, toxins,
        and microorganisms.
        2] Most leucocytes possess at least a limited ability for self
        locomotion.
            a] This allows them to travel through the walls of blood
            vessels and into epithelial and connective tissues.
            b] This type of motion is ameboid and called Diapedesis.
    b] Neutrophils
        1] Neutrophils are the most numerous type of WBC in
            circulation.
        2] They act as phagocytes especially of bacteria.
    c] Monocytes
        1] Monocytes are the second most numerous WBC in circulation.
        2] The monocyte will exit the blood and enter into connective
            tissue where it will mature into the Macrophage.
            a} ex; Langerhans cell, dust cells of the lungs
    d] Basophils
        1] Basophils produce inflammation causing agents such as
        heparin and histamine.
            a} The inflammation response causes blood vessels in the
            affected area to become leakier allowing for easier
            access by WBCs.
    e] Eosinophils
        1] Eosinophils combat the allergic/inflammation response.
            a} They produce agents such as antihistamine which reduce
            edema.
            b} They enter the affected area and feed on antigen-antibody
        tagged invaders and reverse inflammation when the infection
        has been defeated.
    f) Lymphocytes
        1] The lymphocytes are overall the most numerous WBC since
        they fill the lymphoid organs.

      2] There are two classes of lymphocytes:
          a} T Lymphocytes/ T Cells - these cells mature in the
                                    93
                thymus and are involved in cell mediated immunity.
                   1} There are a variety of types of T cells playing
                   different roles in cell mediated immunity.
                       (a) Cytotoxic/Killer T Cells - destroy foreign invaders.
                       (b) Helper T Cells - secrete a variety of agents which
                       increase lymphocyte production and efficiency as
                   well as reducing the reproductive rate and
                   effectiveness of the invader.
                       (c) Suppressor T Cell - secrete agents which end cell
                       mediated immunity when the invasion has been
                       defeated.
                b} B Lymphocytes/B Cells - these cells mature in a still
                undetermined location and are involved in antibody
                mediated immunity.
                   1} Antibodies are produced due to the presence of
                   Antigens.
                       (a) Antigen - any substance which stimulates the
                       production of antibodies.
                            (1) Most antigens are proteins on the cell
                            membrane or cell wall of the invader which your
                            B cells recognize as not being the proteins of
                       your body.
                   2} When a B cell comes in contact with a foreign invader
                   it will under go mitosis producing two lineages of
                   cells specific to that one foreign invader.
                       (a) Plasma Cells - B cells which secrete antibodies
                       specific to the foreign invader.
                            (1) These antibodies will attach to the antigen
                            coating of the invader.
                                [a] Eosinophils recognize the antigen-antibody
                                complex and phagocytize the invader.
                       (b) Memory B cells - B cells which will recognize the
                       same invader if it infects the body again speeding
                   up the body’s immune response.
                            (1) They are stored in the lymphoid tissues of the
                            body.
    3) Life Span and Number
        a] The life span of the typical leucocyte is short due to their
        ingestion of cellular debris, toxins, and bacteria.
            1] They live for days in a healthy person.
            2] They live for only hours in someone combating an infection.
        b] Leucocytes are much less numerous than are erythrocytes.
            1] The ratio is 1 WBC/700 RBC.
d) Thrombocytes                                                 {p. 510, f. 17.7}
    1) The thrombocytes also have a very specialized structure and
    appearance.
        a] They lack a nucleus in the mature state since they are actually
        disc shaped fragments from a large precursor cell called the
    Megakaryocyte.
    2) Function
        a] Thrombocytes serve to prevent blood loss by initiating a series
        of reactions called the “clotting response”.
    3) Life Span and Number
                                             94
           a] Thrombocytes are also short lived cells lasting between 5 to 9
           days on average.
           b] They are also much less numerous than are the erythrocytes.
2. The Plasma
   a) Plasma is the acellular component of blood.
   b) Components:
       1) ~92% water
       2) ~7 to 9% plasma proteins. The Plasma Proteins include:
           a] Albumins
               1] These are the most abundant of the plasma proteins.
               2] They are responsible for blood viscosity and assist in the
           egulation of blood volume by preventing excessive blood
           diffusion into the interstitial tissues.
           b] Globulins
               1] These are the antibody proteins produced by plasma cells.
           c] Fibrinogens
               1] These plasma proteins are involved in the clotting response.
               2] Note : plasma lacking fibrinogen is Serum.
       3) The remaining plasma components are in very low quantities and
       include:
           a] nonprotein substances such as urea, uric acid, and creatine
           b]food substances (amino acids, fatty acids, glycerol, and glucose)
           c] gases (oxygen and carbon dioxide typically)
           d] regulatory substances such as hormones and enzymes.
           e] electrolytes such as Na+, K+, Ca+2, Mg+2, Cl-, HCO3-, SO4-2,
           and PO4-3.

                                    C. Interstitial fluid
1. Although whole blood can not pass through the capillary walls, certain
    components of the plasma will cross the endothelium and become
    interstitial fluid.
    a) Interstital fluid is the fluid between cells in the tissues of the body.
    b) As a result, interstitial fluid is chemically similar to plasma.
        1) The principle chemical difference is that interstitial fluid has a
    lower plasma protein count.
             a] Since the larger plasma proteins can not cross the capillary
        walls.
        2) Materials travel from the blood into the interstitial fluid by
    diffusion.
             a] The exception are the leucocytes which can enter the
        interstitial fluid by diapedesis.
2. The actual composition of interstitial fluid varies from place to place and
    from time to time.
3. Interstitial fluid is also very similar to lymph fluid.
    a) This is because the lymph vessels drain the interstitial fluid from
    the tissues of the body and return it into circulation.
        1) When the fluid is in the lymph vessels it is termed Lymph Fluid.



                                             95
                  CHAPTER 18: CIRCULATION 2; THE HEART

                              A. The Anatomy of the Heart
1. The heart is situated obliquely between the lungs and the mediastinum.
   a) The mediastinum is a mass of tissue found between the pleura of the
   lungs, superior to the heart.
   b) The heart is mostly located posterior to the sternum.
2. The Pericardium                                                   {p. 524, f. 18.3}
   a) The pericardium is divided into the parietal and visceral pericardium.
       1) Although considered to be two separate divisions they are
       confluent with one another.
   b) The Parietal Pericardium/Pericardial Sac is a loose fitting
   membrane which encloses the heart and pericardial space. It has
   two layers:
       1) The Fibrous Layer/Fibrous Pericardium
           a] This is the outer layer of the parietal pericardium.
           b] It is composed of tough, fibrous connective tissue.
           c] It attaches to the large blood vessels of the heart, the
       diaphragm, and to the inside of the sternal wall of the thorax.
           d] It prevents over distension of the heart.
       2) The Serous Layer/Serous Pericardium
           a] This is the inner layer of the parietal pericardium.
           b] It is a much more delicate layer being a serous membrane.
                1] This serous membrane is continuous with the serous
                membrane making up the visceral pericardium.
   c) The Visceral Pericardium is a serous membrane covering the heart.
       1) It is continuous with the serous layer of the parietal pericardium
   and is actually the same membrane.
           a] Between theses two serous membranes is a space called the
           pericardial space.
           b] The two serous membranes secrete serous fluid into the
           pericardial space called pericardial fluid.
                1] Pericardial fluid is a lubricant reducing friction on the
                beating heart.
3. The Heart Wall - is divided into three layers:                    {p. 524, f. 18.3}
   a) Epicardium (or Visceral Pericardium)
       1) This is the outermost layer of the heart wall.
   b) Myocardium
       1) The myocardium is by far the thickest portion of the heart wall.
       2) It is composed of cardiac muscle and is responsible for heart
       contractions.
   c) Endocardium
       1) This is the innermost layer of the heart wall.
       2) It is a layer of endothelium resting on a thin layer of loose c.t.
           a] It is pierced by numerous small blood vessels and in the atria
       by bundles of smooth muscle.
       3) The endothelium of the endocardium s continuous with the
           endothelium lining the blood vessels.
           a] This endothelium also covers the valves of the heart as well as
           the tendons which hold the valves open.
                                                 96
4. The Four Chambers of the Heart                                       {p. 526-7, f. 18.5}
   a) The two upper chambers are the Left and Right Atria.
       1) the atria receive blood from the blood vessels.
       2) Each atrium has an appendage called the Auricle which serves to
       increase the surface area of the atrium.
       3) The endocardium of the atria is modified in the anterior atrial
       walls and in the auricles.
           a] It contains projecting bundles of smooth muscle called
       Pectinate Muscles or Musculi Pectinati.
               1] These bundles of smooth muscle are arranged parallel to one
           another much like the teeth of a comb.
               2] They serve to reinforce the atrial wall.
       4) Separating the left and right atria is the Interatrial Septum.
           a] A prominent feature of the interatrial septum is an oval
       depression called the Fossa Ovalis.
               1] It is located on the septal wall of the right atrium.
               2] It actually represents the occluded remains of the Foramen
               Ovale of the fetal heart.
   b) The two lower chambers are the Ventricles.
       1) The ventricles are larger than are the atria and their walls are
   much thicker with myocardium since they pump the blood into the
   blood vessels for distribution throughhout the body.
           a] They are separated by the Interventricular Septum.
   c) The muscle of the atria and ventricles are separated by fibrous
       connective tissue.
       1) This connective tissue also forms the valves of the heart.
       2) This connective tissue makes up the “cardiac skeleton”.
           a] It divided the myocardium into two muscle masses.
               1] Externally this can be seen on the heart as the Coronary
               Sulcus.
                    a} The coronary sulcus encircles the heart separating the
                    atria and ventricles.
                    b} The coronary sulcus houses the Coronary Sinus and the
                    Circumflex Branch of the Left Coronary Artery.
       3) Externally the right and left ventricles are separated by the
       Anterior and Posterior Interventricular Sulcus.
           a] These two sulci house many of the coronary blood vessels and
           also some fat.
5. The Great Vessels of the Heart                                {p. 526-7, f. 18.5}
   a) Deoxygenated blood enters the right atrium.
       1) The Superior Vena Cava brings blood to the right atrium of the
   heart from all regions of the body superior to the heart.
       2) The Inferior Vena Cava brings blood to the right atrium of the
       heart from all regions of the body superior to the heart.
       3) The Coronary Sinus drains the coronary veins and bring the blood
       into the right atrium.
   b) The right atrium sends blood to the right ventricle.
       1) The right ventricle sends the blood into the Pulmonary Trunk.
           a] The pulmonary trunk divides into the Right and Left Pulmonary
           Arteries which travel to the lungs.
   c) The now oxygen rich blood is returned to the heart by the four
   Pulmonary Veins which drain into the left atrium.
   d) The left atrium sends blood to the left ventricle which will then
                                               97
   pump the blood into the Ascending Aorta.
        1) The ascending aorta serves to carry the oxygenated blood to the
        tissues of the body.
            a] The blood is passed into the arch of the aorta and then the
            descending aorta.
            b] The coronary arteries will also branch off from the ascending
        aorta.
6. The Valves of the Heart                                       {p. 526-7, f. 18.5}
   a) The valves serve to prevent blood from flowing backwards.
   b) The Atrioventricular Valves - lay between the atrium and the
   ventricle on both sides of the heart. They prevent the backflow of
   blood from the ventricle into the atrium.
        1) The Right Atrioventricular Valve
            a] The right AV valve is also known as the Tricuspid Valve since
            it has three flaps or Cusps.
                 1] The cusps are composed of fibrous c.t. outgrowths from the
                 cardiac skeleton covered by endothelium.
                 2] The Chordae Tendineae are c.t. cords which connect the
                 downward pointing tips of the cusps to small, conical
            projections of the ventricular wall called Papillary Muscles.
            b] The right AV valve prevents the backflow of blood from the
        right ventricle into the right atrium.
        2) The Left Atrioventricular Valve
            a] The left atrioventricular valve has only two cusps so it is also
        known as the Bicuspid Valve.
                 1] It is also known as the Mitral Valve.
            b] Structurally it is similar to the right AV valve.
                 1] It is composed of fibrous c.t. covered by endothelium.
                 2] It has chordae tendineae and papillary muscles.
            c] The left AV valve prevents the backflow of blood from the
            left ventricle into the left atrium
   c) The Semilunar Valves - are found in the arteries exiting the two
   ventricles and serve to prevent the backflow of blood into the
   ventricles.
        1) Both valves have three cusps of fibrous c.t., covered by
   endothelium, attached to the arterial wall.
        2) Pulmonary Semilunar Valve - located on the wall of the pulmonary
        trunk it prevents the backflow of blood from the pulmonary trunk
   into the right ventricle.
        3) Aortic Semilunar Valve - located on the wall of the aorta it
   prevents the backflow of blood from the pulmonary trunk into the
   left ventricle.


                                    B. The Heart Beat
1. The Cardiac Conduction System                                       {p. 533 f. 18.12}
   a) The heart is innervated by the ANS but the ANS only serves to
       increase or decrease the heart rate, it does not initiate contraction.
       1) Contraction can occur even without any direct nervous stimulus
   since the heart has its own, intrinsic regulation system termed
   the cardiac conduction system.
           a] The conduction system has specialized cardiac muscle tissue
                                             98
           able to produce and transmit an impulse.
               1] This specialized tissue is called Nodal Tissue.
               2] All cardiac muscle cells have their own inherent rythmicity
           and nodal tissue advances that.
   b) The Nodes of the Heart - A node is a compact mass of conductive
   cardiac muscle cells.
       1) Sinoatrial Node/S A Node - is the “pacemaker” of the heart.
           a] It is located on the right atrial wall inferior to the opening of
       the superior vena cava.
           b] The S A node initiates each cardiac cycle, setting the heart
       rate.
               1] Normally it will cause the heart to beat at about 72 beats
           per minute but it can be affected by the ANS or by certain
           blood-borne chemicals (ex, epinepherine).
           c] Once a impulse is initiated by the S A node it spreads out over
           both atria.
               1] This causes the atria to contract (systole).
                     a} Meanwhile the ventricles are relaxed (diastole).
               2] It will also cause the atrioventricular node to depolarize.
       2) Atrioventricular Node/A V Node
           a] The A V valve is located on the right atrial wall on the
       interatrial septum near the tricuspid valve.
           b]When the A V node fire it sends an impulse out to the ventricles.
               1] This will cause ventricular systole.
                     a} Meanwhile the atria are now in diastole.
   c) The impulse generated by the A V node is carried by a network of
   conducting fibers within the walls of the ventricles. This is
   necessary due to the thickness of the ventricular myocardium.
       1) The Atrioventricular Bundle or Bundle of His runs from the A V
       node into the interventricular septum where it branches into . .           2)
Right and Left Bundle Branches which run down the
   interventricular septum towards the apex distributing the charge
   through the medial walls of the ventricles.
       3) The impulse continues into the Purkinje Fibers which distribute
   the impulse to the lateral ventricular walls and initiate
   contraction of the ventricles.
2. Autonomic Control of the Heart Beat
   a) ANS control allows for the modification of the heart rate to better
   serve the needs of the body.
       1) The Cardioacceleratory Center of the medulla oblongata sends
       sympathetic fibers to the sympathetic trunk.
           a] Where the neurons synapse with neurons of the Cardiac Nerve
           which innervates the S A node as well as the A V node and
           ventricular walls.
               1] It will stimulate an increase in the heart rate by releasing
           norepinepherine.
       2) The Cardioinhibitory center of the medulla oblongata sends
       parasympathetic fibers to the heart via the Vagus Nerve to the
           S A and A V nodes.
           a] It causes a decrease in heart rate through the release of
           acetylcholine.
   b) Sensory centers throughout various portions of the cardiovascular
   system guide the ANS balance of parasympathetic and sympathetic
                                                99
control of the heart rate.
   1) One such are Baroreceptors (aka; pressoreceptors) respond to
   changes in blood pressure.




                                     100
              CHAPTER 19: CIRCULATION 3; BLOOD VESSELS

                                  A. The Blood Vessels
1. Introduction                                                           {p. 545, f. 19.1}
    a) There are three classes of blood vessels: arteries, veins, and
    capillaries.
        1) Arteries serve to carry blood from the heart to the tissues of the
    body.
        2) Capillaries are the microscopic blood vessels of the tissues
        where materials are exchanged between the tissues and the blood.
        3) Veins serve to carry blood back to the heart from the body’s
        tissues.
    b) The larger arteries and veins have three tunics.
        1) The Innermost is the Tunica Intima/Tunica Interna which is in
        direct contact with the blood.
            a] Typically it will have a lining of endothelium supported by
            areolar c.t.
        2) The second tunic is the Tunica Media.
            a] This tunic will contain smooth muscle.
        3) The outermost tunic is the Tunic Externa/Tunica Adventitia.
            a] This outermost layer is composed primarily of loose c.t.
            b] It also will have numerous small blood vessels which service
            the larger arteries and veins.
                1] These vessels are called the Vasa Vasorum and service the
                tissues of these blood vessels.                    {p. 546, f. 19.2}
                2] They will penetrate the tunica adventitia and tunica media
            and partially enter into the tunica intima in some cases.
2. Arteries                                                               {p. 546, f. 19.2}
    a) The arteries carry blood from the heart to the tissues of the body.
        1) They will be the thickest of the blood vessels since they carry
        blood under its highest pressure.
        2) Due to their structure arteries have two major properties:
    elasticity and contractility.
            a] Elasticity due to their component of elastic fibers.
                1] This allows arteries to handle a large flow of blood.
            b] Contractility due to their component of smooth muscle.
                1] The smooth muscle will be arranged both longitudinally and
                circularly.
                2] The smooth muscle is innervated by the sympathetic
                division of the ANS.
                     a} Vasodilation is due to sympathetic suppression.
                     b} Vasoconstriction is due to sympathetic firing.
    b) The three tunics of the artery:
        1) Tunica Intima/Tunica Interna - the innermost layer, it lines the
    lumen. It has three portions:
            a] Endothelium (simple squamous epithelium) - the innermost
            b] Areolar Connective Tissue - the middle
            c] Elastic Connective Tissue which forms the Internal Elastic
            Membrane - the outermost portion.
        2) Tunica Media - the middle and thickest layer it is composed of
                                                101
       smooth muscle and elastic fibers.
       3) Tunica Externa/Tunica Adventitia - the outermost tunic.
           a] It is composed primarily of loose c.t. but it will also contain
           bundles of smooth muscle and elastic c.t.
           b] In some arteries the tunica media and externa are separated by
           an External Elastic Membrane.
   c) There are three classes of arteries:
       1) Elastic Arteries/Conducting Arteries
           a] These are the largest arteries such as the aorta, subclavian,
       brachiocephalic,common carotid, vertebrals, and common iliac
           arteries.
           b] Compared to other artery classes, they are thin walled relative
           to their diameter.
               1] This is because their tunica media has less smooth muscle
               and more elastic fibers.
                    a} After all, they are receiving blood under its highest
                    pressure.
           c] Actions of Elastic Arteries:
               1] When the ventricles contract and force blood out of the
               heart the walls of the elastic arteries expand.
               2] During ventricular diastole the elastic arterial walls recoil
           helping to propel the blood further in circulation.
       2) Muscular Arteries/Distributing Arteries
           a] These are medium sized arteries such as the axillary, brachial,
           radial, intercostal, splenic, mesenteric, femoral, popliteal and
       tibial arteries.
               1] They branch off of the elastic arteries.
           b] These are the thickest walled of the arteries since their tunica
       media contains much smooth muscle (and fewer elastic fibers).
               1] This allows the muscular artery to adjust the volume of
               blood to suit the needs of the structure it is supplying with
           blood through vasoconstriction and vasodilation.
       3) Arterioles
           a] These are the smallest of the arteries.
               1] They branch off of the muscular arteries and other
           arterioles.
           b] They serve to deliver blood to the capillaries.
           c] Structurally, arterioles will be similar to other arteries.
               1] The larger arterioles display all three tunics and they will
           be histologically similar to those of the typical artery..
                    a} The tunica media will have more smooth muscle than
                    elastic fibers.
               2] As the arterioles get smaller in size, as they approach the
           capillary bed, their tunics begin to change:
                    a} Those arterioles closest to the capillaries will have only
                    the endothelium of the tunica intima and a few, scattered
                    smooth muscle cells.
           d] Their main function is to control the flow of blood from the
           arteries to the capillaries.
               1] Vasoconstriction reduces the blood flow to the capillaries.
               2] Vasodilation increases the blood flow to the capillaries.
3. Capillaries                                                {p. 548-9, f. 19.4}
                                            102
   a) Capillaries are microscopic vessels which allow for the exchange of
   materials between the blood and the cells of the tissues.
       1) They usually connect arterioles and venules.
       2) They are found near almost every cell of the body.
           a] Although their numbers increase with areas of higher activity.
       3) At the point where blood is entering a capillary bed there is a
       smooth muscle band called the Precapillary Sphincter which
   controls the flow of blood into the capillary bed.
       4) The functional nature of the capillary is reflected in:
           a] their extensive branching which allows them to service more
       cells
           b] and their structure which is a wall made up only of endothelium
       to prevent as little of a barrier to diffusion as possible.
   b) Capillaries can be classified by structure:
       1) Continuous Capillaries
           a] These are the most numerous and widely distributed class of
       capillary.
           b] They are called “continuous” because cross sections of the
       cytoplasm of their endothelial cells appear as an uninterrupted
       rings.
       2) Fenestrated capillaries/Discontinuous Capillaries
           a] The endothelial cells of these capillaries have numerous
           fenestrae (or pores) where the cytoplasm is absent.
               1] This arrangement provides even less of a barrier to
               diffusion.
           b] There are two types:
               1] In most fenestrated capillaries, the fenestrae are covered
           by a thin diaphragm composed of the fused cell membranes.
                   a} These are termed Diaphragmated Fenestrated Capillaries.
                   b} Ex; the villi of the small intestine
               2] Some fenestrated capillaries which need to provide even
           less of a barrier to diffusion lack the diaphragms.
                   a}These are called Undiaphragmated Fenestrated Capillaries.
                   b} Ex; the kidney
       3) Sinusoids
           a] Sinusoids are microscopic blood vessels found in certain
           regions of the body (ex; liver) which may or may not be true
       capillaries.
               1] Like capillaries they:
                   a} are microscopic
                   b} involved in the exchange of materials
                   c} have a wall composed of endothelium and no other blood
                   vessels tunics.
               2] Unlike capillaries they:
                   a} have a wider lumen
                   b} have their fenestrae guarded by macrophages called
                   Kupffer Cells.
4. Veins
   a) Veins serve to return the blood to the heart from the tissues of the
   body.
       1) They will also have three tunics making up their walls typically.
       a] The walls will be thinner walled than will those of the same
           sized artery since they are carrying blood under a much lower
                                                103
       pressure.
               1] By the time the blood has reached the veins it has lost a
          great deal of the pressure generated by the heart.
                   a} This is why medium and large veins will also have valves
                   to prevent the backflow of blood.              {p. 551, f. 19.5}
   b) Venules
       1) Venules are tiny veins which drain the capillary beds.
       2) Structure:
          a] Venules closest to the capillary beds will have only a tunica
          intima of endothelium and a thicker tunica adventitia of loose
       connective tissue.
          b] Larger venules will also have a tunica media.
   c) Veins (Also referred to as medium and large veins.)
       1) Veins have essentially the same three tunics as do arteries.
          a] However, their tunica media has considerably less muscle and
          elastic tissue and more white, fibrous connective tissue.
               1] Their smooth muscle and elastic fiber component, although
               less, is enough to allow them to adjust to changes in blood
          flow.
          b] The tunica intima has valves projecting o into the lumen which
               prevent the backflow of blood.
               1] This is a problem since blood is under lower pressure in the
               veins.
                   a} So we see more valves in the veins of the legs which
                   must fight gravity to return the blood to the heart.
   d) Sinuses (aka; Vascular Sinuses or Venous Sinuses)
       1) Sinuses are large, specialized veins having only a thin endothelium
       and no smooth muscle component to alter its diameter.
          a] Instead the surrounding tissues replace the tunica media and
       externa.
       2) Ex; intracranial sinus, coronary sinus


                                  B. Circulatory Routes
1. Systemic Circulation - the flow of blood from the left ventricle to all
   portions of the body (except the lungs) and back to the right atrium.
   a) Its purpose is to carry oxygen and nutrients to the tissues and to
   remove carbon dioxide and other wastes from the tissues.
   b) Route
        1) Blood leaves the left ventricle via the aorta.
            a] Many arteries branch off of the aorta to the tissues.
                1] These arteries are termed Systemic Arteries.
        2) Veins drain the capillary beds ultimately into the superior and
        inferior vena cava which, in turn, drain into the right atrium.
            a] These veins are termed Systemic Veins.
   c) One division of systemic circulation is Coronary Circulation.
        1) Coronary circulation supplies the walls of the heart with
        nutrients and removes wastes.

      2) The Coronary/Cardiac Circulatory Route
          a] The left coronary artery comes off of the ascending aorta and
          divides into the anterior interventricular branch and the
                                            104
        circumflex branch.
                1] The anterior interventricular branch supplies the walls of
            both ventricles.
                2] The circumflex branch supplies the walls of the left
            ventricle and left atrium.
            b] The right coronary artery also comes off of the ascending aorta
                and it divides into the posterior interventricular branch and
        the marginal branch.
                1] The posterior interventricular branch supplies the walls of
            both ventricles.
                2] The marginal branch supplies the walls of the right atrium
            and right ventricle.
   d) Another division of systemic circulation is the Hepatic Portal
   System.
        1) The hepatic portal system refers to the flow of nutrient rich,
        deoxygenated blood from the stomach, small intestine, and large
   intestine to the liver.
            a] The liver receives oxygenated blood through systemic circulation.
        2) This allows the liver to monitor substances entering into
   circulation from the digestive system.
            a] It also allows the liver to screen out toxins ingested with food
   before they enter into circulation.
        3) Blood leaves the liver and enters the inferior vena cava by way of
        the hepatic veins.
2. Pulmonary Circulation - the flow of blood from the right ventricle to
   the lungs and then back to the left atrium.
   a) Its purpose is to pick up oxygen from the lungs and to dump carbon
   dioxide into the lungs.
   b) Route
        1) Blood leaves the heart from the right ventricle and enters the
   pulmonary trunk.
            a] The pulmonary trunk branches into the right and left pulmonary
            arteries to bring blood to the right and left lungs respectively.
            b] The arteries branch into smaller and smaller vessels.
            c] Capillaries beds exchange gases between the blood and the
            alveoli of the lungs via diffusion.
        2) The capillaries drain into venules which drain into larger and
        larger veins.
        3) The four pulmonary veins return the oxygenated blood to the left
        ventricle of the heart.




                                           105
                    CHAPTER 20: THE LYMPHATIC SYSTEM

                                      A. Introduction
1. The lymphatic/lymphoid system consists of:lymph fluid, lymph vessels,               lymph
nodes, and lymphoid organs.
   a) The lymphoid organs are: tonsils, spleen, and thymus.
2. The main purpose of the lymphatic system is to drain from the tissues a
   protein rich fluid which has escaped from the blood vessels.
   a) This fluid is interstitial fluid and it can not be returned to the blood
   stream directly.
       1) It may contain pathogens which have penetrated the tissues.
           a] So, foreign invaders are removed from the fluid and antibodies
           to deal with these invaders are added before it is allowed to
       return to blood vessels.
   b) The lymphatic system also serves to:
       1) transport fats from the intestine into the blood
       2) produce lymphocytes
       3) and produce antibodies.


                     B. Lymph Vessels and Lymph Circulation
1. Lymph Capillaries                                                     {p. 585, f. 20.2}
   a) Lymph capillaries represent the starting point of lymph
   circulation.
       1) They are blind ended tubes in the intercellular spaces of the
       tissues that pick up interstitial fluid.
           a] At this time the fluid is called Lymph/Lymph Fluid.
   b) Lymph capillaries are found in all vascularized tissues excepting:
   splenic pulp, bone marrow, and the CNS.
   c) Structurally, lymph capillaries are similar to blood capillaries.
       1) Their walls are composed of endothelium.
       2)] Unlike blood capillaries, they are more permeable, have a larger
       lumen, and have numerous small valves.
2. Lymphatics
   a) Lymph capillaries will converge into larger and larger lymph vessels
   called lymphatics.
   b) Lymphatics are structurally similar to veins but they have thinner
   walls, more valves, and contain lymph nodes at various points.
3. Lymph Trunks
   a) The lymphatics will converge into the lymph trunks.
   b) The principle lymph trunks are: lumbar, intestinal,
   bronchomediastinal, subclavian, and jugular trunks.
4. Lymphatic Ducts                                                {p. 587, f. 20.3}
   a) The principle lymph trunks drain lymph into two main channels:
       1) The Left Lymphatic/Thoracic Duct - receives lymph from the left
   side of the body superior to the diaphragm and all of the body
   inferior to the diaphragm.
           a] It is the main collecting duct of the lymphatic system.
           b] It returns the lymph to blood circulation at the left subclavian
                                                106
       vein.
       2) The Right Lymphatic Duct - receives lymph from the right
   side of the body superior to the diaphragm.
           a] It returns the lymph to blood circulation at the right subclavian
           vein.
5. Lymph circulation is maintained by the contractions of skeletal muscles             and
by respiratory movements.


                                    C. Lymph Nodes
1.Structure                                                        {p. 588, f. 20.4}
   a) Lymph nodes are small bean shaped structures averaging between
       1 and 25 mm in length.
   b) You can divide the structure of the lymph node into the stroma and
   the parenchyma.
       1) The stroma is the supporting framework of the lymph node:
           a] Hilus - a slight depression on one side of the lymph node where
           the efferent lymphatic exits the node.
           b] Capsule - a capsule of fibrous c.t. covering the node. It also
       extends into the node.
           c] Trabeculae - fibrous c.t. extensions of the capsule located
           within the node.
       2) The parenchyma is the working tissues of the lymph node.
           a] It is composed primarily of lymphoid cells, lymphocytes and
           macrophages, and can be divided into the cortex and medulla.
           b] Cortex - the outer zone of the parenchyma.
                1] It is composed of densely packed lymphocytess arranged into
           spherical masses called Lymph Nodules.
                     a} Lymph nodules will often contain pale staining centers
                called Germinal Centers where more lymphocytes are
                being produced.
           c] Medulla - the inner zone.
                1] It is acentric so that the medulla is in contact with the
                hilus.
                2] It is composed of lymphoid cells arranged into strands along
           the trabeculae.
                     a} These strand-like arrangements of lymphoid cells are
                called Medullary Strands/Cords.
                         1} They contain primarily the macrophage of the lymph
                         node, the Reticuloendothelial Cells.
2. Lymph Circulation in the Lymph Node
   a) Afferent lymphatics bring the lymph to the node.
   b) The lymph enters into a series of sinuses within the node.
       1) It first enters the Capsular/Subcapsular Sinus between the
       capsule and the cortex.
       2) It then percolates into the Cortical Sinuses where it picks up
       plasma cells and other lymphocytes.
       3) From there is passes into the Medullary Sinuses where the
       reticuloendotheliail cells remove foreign invaders from the lymph.
   c) The lymph fluid then passes on to the hilus where it exits the lymph
   node through the efferent lymphatic.
                                             107
                                  D. Lymphoid Organs
1.Tonsils                                                        {p. 598, f. 20.11}
   a) The various tonsils can be collectively described as masses of
   lymphoid tissue embedded in mucous membrane.
        1) Like lymph nodes they are filled with lymphoid cells, both
   lymphocytes and macrophages.
        2) They will have crypts leading into them from the surface of the
   mucous membrane.
            a] If food becomes trapped in the crypt it can cause tonsillitis.
   b) The Types of Tonsils
        1) Palatine Tonsils - located in the tonsillar fossa between the
        glossopalatine and pharyngopalatine arches.
            a] They are commonly removed during tonsillectomies.
        2) Lingual Tonsils - located at the base of the tongue.
            a] They may also be removed during tonsillectomies
        3) Pharyngeal Tonsils - located in the posterior nasopharynx.
            a] They are referred to as the 'adenoids” when enlarged.
            b] They are rarely removed during tonsillectomies.
2. Spleen                                                        {p. 596, f. 20.9}
   a) The spleen is the largest mass of lymphoid tissue in the body.
   b) It is located in the left hypochondric region between the fundus of
   the stomach and the diaphragm.
   c) Structure:
        1) Stroma
            a] The spleen has a capsule of fibrous c.t. with some smooth
            muscle.
                1] Because it is located in the abdominopelvic cavity, the
                spleen will also be covered by the peritoneum which will be
            external to the capsule.
            b] The spleen will also have trabeculae.
            c] The spleen will also have a hilus where are located the splenic
            artery and splenic vein.
        2) Parenchyma - consists of white pulp and red pulp.
            a] White Pulp - this is the lymphoid tissue arranged around
            arteries in the spleen.
                1] The clusters of lymphoid cells are arranged spherically
                around the artery forming the Splenic Nodules/Malpighian
            Corpuscles.
                    a] These lymphoid cells are primarily lymphocytes.
            b] Red Pulp - this is the lymphoid tissue arranged around the veins .
        1] The lymphoid cells are arranged into strands between venous
        sinuses forming the Splenic Cords/Billroth’s Cords.
   d) Functions
        1) The spleen has splenic blood vessels but lacks splenic lymph
        vessels so the spleen does not filter lymph. Instead it filter
   blood.
            a] It phagocytizes bacteria and helps to recycle senescent blood
        cells.
        2) The spleen produces lymphocytes and plasma cells.
            a] Plasma cells will produce antibodies.
        3) The spleen stores and releases blood.
                                              108
            a] The storage and release of blood from the spleen is under
            sympathetic control.
3. Appendix
   a) The appendix is not technically an organ, instead it is a mass of
   lymphoid cells located at the junction between the small and large
   intestines.
        1) It is actually an outgrowth of the cecum of the large intestine.
        2) Like the tonsils, it has crypts.
            a] If matter becomes trapped in the crypt it can cause
            appendicitis.
4. Thymus                                                                {p. 597, f. 20.10}
   a) The thymus is a bilobed mass found in the upper thoracic cavity along
   the trachea and superior to the aortic arch.
   b) The thymus is at its largest in children.
        1) It begins to shrink with the onset of puberty.
            a] The parenchyma also begins to be replaced by fat.
   c) Its role in the immune response is to serve as the site of maturation
   for the T lymphocytes.
        1) It also releases a hormone called Thymosin which helps in the
        immune response.




                                             109
                 CHAPTER 21: THE RESPIRATORY SYSTEM

                                      A. Introduction
1. The cells of our body require a continuous supply of oxygen to meet
   their metabolic demands.
   a) At the same time, they are producing carbon dioxide which must be
   removed from the body.
   b) The respiratory system is the system by which oxygen is brought into
   our bodies and carbon dioxide is removed.
       1) The respiratory system works in close association with a second
   system the circulatory system to allow for the exchange of gases
   at the tissue level.
2. Respiration is described as the overall exchange of gases between the
   atmosphere, the blood, and the cells. It has four processes:
   a) Ventilation (or breathing) - is the exchange of gases between the
   atmosphere and lungs.
   b) External Respiration - is the exchange of gases between the lungs
   and the blood.
   c) Internal Respiration - is the exchange of gases between the blood and
   the tissues/cells.
   d) Cellular Respiration - is the burning of food to release energy (ATP).
       1) It occurs in the mitochondria.


                            B. The Organs of Respiration
1.The Nose                                                {p. 605-6, f. 21.2, 21.3}
   a) The nose has both an external and an internal portion.
       1) The external portion, external to the skull, is supported by a
       flexible cartilagenous frame work accompanying a bony frame
       covered by skin and lined internally by mucus membrane.
           a] It has two openings called the External Nares or Nostrils.
       2) The internal portion is a large cavity located within the skull
       called the Nasal Cavity.
           a] It is located inferior to the cranium and superior to the mouth.
           b] Anteriorly it communicates with the external nose.
           c] Posteriorly it communicates with the pharynx through two
           openings called the Internal Nares or Choanae.
           d] Four paranasal sinuses also open into the nasal cavity as does
           the nasolacrimal duct.
               1] The four sinuses are the frontal, sphenoidal, maxillary, and
               ethmoidal.
   b) The nose is divided into a right and a left nasal cavity by a vertical
   partition called the Nasal Septum.
       1) The septum is composed of cartilage anteriorly and bone
   posteriorly (ethmoid and vomer).
       2) At the anterior portions of the two nasal cavities, immediately
       within the nostrils, are the Vestibules.
           1) These vestibules are surrounded by the cartilage of the
           external nose.
                                               110
   c) The structures within the nose primarily serve three functions:to
   warm, filter, and moisten the air entering the nose. They also serve in
   olfaction and aid in speech.
       1) Air passes into the external nares and through the vestibules
       first.
            a] The vestibular epithelium contains hair follicles which help to
       filter the air.
       2) The air then passes into the rest of the nasal cavity.
            a] The walls of the nasal cavity have three projections on each
       side formed by the conchae.
                1] As a result the nasal cavity is dived into three groove like
            passages called the Superior, Middle, and Inferior Nasal
            Meatuses.
                     a} This increase the surface area of the nasal cavity making
                     the nose more efficient at warming, filtering, and
                moistening the air.
            b] The walls of the nasal cavity are lined by a mucus membrane.
                1] The epithelium is a pseudostratified ciliated columnar
                epithelium with goblet cells.
                     a} The goblet cells secrete mucus which traps particulate
                     matter and moistens the air.
                        1} The moistening of the air is also assisted by drainage
                        from the nasolacrimal ducts.
                     b} The cilia on the columnar cells help to remove
                     particulate matter trapped in mucus.
                2] The underlying areolar c.t. is very well vascularized.
                     a} The numerous capillaries radiate heat to warm the air.
   d) Blood and Nerve Supply to the Nose
       1) Blood Supply
            a] Arterial supply to the nasal cavity is principally from the
            sphenopalatine branch of the maxillary artery.
            b] The veins of the nasal cavity drain into the sphenopalatine,
            facial, and ophthalamic veins.
       2) Nerve Supply
            a] Trigeminal nerve
            b] Olfactory cells and olfactory nerve for detection of olfaction
2. The Pharynx                                                      {p. 606, f. 21.3}
   a) General
       1) The pharynx begins at the internal nares and extends down the
   neck to the level of the glottis.
       2) The pharynx communicates with the nose, mouth, trachea, and
   esophagus so it serves as a common passageway for air and food.
       3) Its walls are composed of skeletal muscle lined with a mucus
       membrane.
            a] The nature of the mucus membrane varies regionally.
       4) There are three divisions to the pharynx: Nasopharynx, Oropharynx,
   and Laryngeopharynx.
   b) The Nasopharynx
       1) The nasopharynx is the superior most portion of the pharynx.
            a] It lays posterior to the nasal cavity and extends to the level of
       the soft palate.
       2) It has four openings in its walls: the two internal nares and the
       two eustachian tubes.
                                               111
            a] The nasopharynx will exchange air with the eustachian tubes to
       stabilize air pressure within the head.
       3) The posterior wall of the nasopharynx contains the pharyngeal
   tonsils.
       4) The epithelium is a pseudostratified ciliated columnar epithelium
   with goblet cells, same as the nasal cavity.
   c) The Oropharynx
       1) This is the middle portion of the pharynx.
            a] It extends from the soft palate to the level of the hyoid bone.
       2) It has only one opening, the Fauces, from the mouth.
       3) Since food passes through the oropharynx, it is lined by stratified
       squamous epithelium.
       4) It contains both the palatine and lingual tonsils.
   d) The Laryngeopharynx
       1) The laryngeopharynx is a short, inferior most segment running
       from the level of the hyoid to the larynx and esophagus..
       2) Since food also passes through the laryngeopharynx, it is lined by
   stratified squamous epithelium.
   e) Blood and Nerve Supply
       1) Blood Supply
            a] Arterial Supply to the pharynx is handled by the ascending
            pharyngeal and ascending palatine branches of the facial, the
       descending pharyngeal and descending palatine branches of the
       maxillary, and the branches of the superior thyroid arteries.
            b] The veins drain into the pterygoid plexus and internal jugular
       veins.
       2) Nerve Supply
            a] Most of the pharyngeal muscles are innervated by the
       pharyngeal plexus which includes branches from the
       glossopharyngeal, vagus, and superior cervical sympathetic
   ganglion.
3. The Larynx                                                              {p. 609 f. 21.5}
   a) The larynx is a short passageway that connects the pharynx and the
   trachea.
       1) It lays anterior to cervical vertebrae 4, 5, and 6.
   b) The walls of the larynx are supported by nine pieces of cartilage,
   three paired and three singular.
       1) Thyroid (commonly called the “Adam’s apple) - a singular
   cartilage consisting of two fused plates of cartilage which form
   the anterior wall of the larynx and gives it a triangular shape.
       2) Epiglottis - a large singular, leaf shaped cartilage found on top of
       the larynx, attached to the thyroid cartilage.
            a] During swallowing the epiglottis blocks the opening into the
            trachea, called the Glottis.
       3) Cricoid - a singular, ring shaped cartilage forming the inferior
       walls of the larynx.
            a] It is attached to the first tracheal ring by the cricotracheal
       ligament.
       4) Arytenoid - a pair of pyramid shaped cartilages found at the
            superior border of the cricoid cartilage.
            a] The vocal folds and pharyngeal muscles attach to the arytenoid
            cartilages.
                1] So they are involved in the movements of the vocal cords.
                                                112
       5) Corniculate - a pair of cone shaped cartilages located at the apex
       of the arytenoid cartilages.
       6) Cuneiform - a pair of rod shaped cartilages located within the
       mucus membrane folds connecting the epiglottis to the arytenoids.
   c) The epithelial lining of the larynx is psuedostratified ciliated
   columnar epithelium with goblet cells.
       1) So it also plays a role in trapping and removing particulate matter.
       2) This mucus membrane also forms two pairs of folds:
           a] Ventricular Folds (false vocal cords) - the upper pair they are
       simply folds of the mucus membrane.
           b] Vocal Folds (true vocal cords) - the lower pair.
               1] They are also folds of the mucus membrane but they also
           contain:
                   a} bands of elastic ligaments which stretched between the
                   cartilages.
                   b} intrinsic skeletal muscles which are attached to both the
               folds and the cartilages.
               2] Movement of the vocal folds regulate the amount of air
               passing through the trachea/larynx.
   d) Blood and Nerve Supply
       1) Blood Supply
           a] The arterial supply comes from the superior and inferior
           laryngeals as well as the cricothyroid artery.
           b] The blood is drained by the superior and inferior thyroid veins.
       2) Nerve Supply
           a] The nerves are the superior and recurrent laryngeal branches of
       the vagus nerve.
4. Trachea                                                              {p. 612 f. 21.8}
   a) The trachea extends from the larynx to the first pair of bronchi.
   b) Structure
       1) The trachea is lined internally by psuedostratified ciliated
   columnar epithelium with goblet cells.
           a] It provides some protection against particulate matter.
       2) The walls are composed of smooth muscle and elastic c.t.
           a] The smooth muscle is called the Trachealis muscle.
               1] The trachealis receives parasympathetic innervation from
           the vagus.
       3) The walls also have reinforcing C-shaped cartilage rings.
           a] The open portions of the “C” face the esophagus.
               1] Stretching between the open ends of the “C”s is the
               trachealis muscle.
           b] They provide rigid support to prevent collapsing due to vacuum
           pressure.
5. The Bronchi                                                          {p. 613 f. 21.8}
   a) The bronchi are branching respiratory passageways beginning with
   the division of the trachea into the two Primary Bronchi.
       1) The primary bronchi divide into smaller bronchi which divide and so
       on.
   b) Structurally bronchi are similar to the trachea.
       1) The bronchus is lined internally by psuedostratified ciliated
       columnar epithelium with goblet cells.
       2) The walls are composed of smooth muscle and elastic c.t
       3) The bronchus also have reinforcing cartilage but they are in
                                              113
       complete rings.
   c) The Primary Bronchi
       1) The right and left primary bronchi branch off of the trachea and
   enter into the lungs.
   d) The Secondary Bronchi/Lobar Bronchi
       1) The secondary bronchi branch off of the primary bronchi and enter
       into the lobes of the lungs.
           a] One secondary bronchus goes to each lobe, there are three in the
       right lung and two in the left lung.
   e) The Tertiary Bronchi/Segmental Bronchi
       1) The tertiary bronchi branch off of the secondary and go to each
   segment of the lung.
6. The Bronchioles
   a) The bronchioles are smaller respiratory passageways branching off
   of the tertiary bronchi and other bronchioles.
       1) Structurally they are overall similar to the bonchi but there are
   some differences:
           a] The cartilage rings are replaced by cartilage plates.
           b] The amount of smooth muscle increase in the smaller branches.
           c] The epithelium switches to a simple columnar in primary
           bronchi then to a simple cuboidal in the terminal bronchi.
   b) The bronchioles branch into smaller and smaller passageways to
   handle smaller subunits of the lungs.
       1) Primary bronchioles branch off of the tertiary bronchi.
       2) Secondary bronchioles branch off of the primary bronchioles.
       3) Tertiary bronchioles branch off of the secondary bronchioles.
       4) Terminal bronchioles branch off of the tertiary bronchioles.
NB -> the trachea, bronchi, and bronchioles form the respiratory tree.
7. The Lungs                                          {p. 618-19 f. 21.12-13}
   a) General
       1) The lungs are a pair of cone shaped organs located in the thoracic
       cavity separated by the mediastinum and the heart.
       2) Two layers of serous membrane enclose and protect each lung.
           a] Collectively they are called the Pleural Membranes.
           b] There are two layers:
               1] Parietal Layer - this is the outer layer. It attaches to the
           walls of the thoracic cavity.
               2] Visceral Layer - this is the inner layer. It covers, and is
               attached to, the lungs.
           c] Between the two layers is the pleural space into which these
       serous membranes secrete pleural fluid.
               1] Serous fluid serve as a lubricant to reduce friction on the
           lungs.
       3) Gross Appearance of the Lung
           a] The lungs extend from the diaphragm to a point slightly
           superior to the clavicles.
               1] The Base is the broad inferior portion. It is concave to fit
           over the convex diaphragm.
               2] The Apex is the narrow superor portion of the lung.
                   a} aka; Cupola.
               3] The Costal Surfaces are the surfaces of the lungs facing the
               ribs (i.e.; anterior, lateral, and posterior).
               4] The Mediastinal/Medial Surface faces the mediastinum.
                                                114
                    a} On the mediastinal surface is a concave depression called
                        the Hilus where the pulmonary blood vessels and primary
                    bronchi meet the lung.
                    b} On the mediastinal surface of the left lung is a concave
                    depression called the Cardiac Notch where the heart lays
           b] Each lung is broken up into lobes, segments, and lobules so as
               to increase surface area.
               1] The lobes are separated by Fissures.
                    a} The Oblique Fissure is found on both lungs and separates
                    the Superior and Inferior Lobes.
                    b} The right lung also has the Horizontal Fissure which
                    separates the Superior and Middle Lobes giving the right
               lung an extra lobe.
               2] Each lobe has its own secondary bronchus.
   b) Within each lung the terminal bronchioles subdivided into microscopic
   branches called Respiratory Bronchioles.                   {p. 615 f. 21.9}
       1) The respiratory bronchioles are lined internally by simple cuboidal
       epithelium. closer to the terminal bronchioles and by simple
   squamous in the smaller portions.
       2) The respiratory bronchioles branch into the Alveolar Ducts/Atria.
   c) The alveolar ducts lead to the Alveolar Sacs/Alveoli.
       1) The walls of the alveolus are composed of two cell types:
           {p. 615 f. 21.10}
           a] Type 1 Alveolar Cells - low squamous epithelial cells forming a
           continuous lining for the alveolar wall.
               1] Their low height helps in the diffusion of gases.
           b] Type 2 Alveolar Cells - low cuboidal epithelial cells found
           interdigitating the Type 1 cells.
               1] They are secretory cells producing a phospholipid surfactant
                    which reduces surface tension.
       2) The alveoli also contain a third cell type, the Alveolar
       Macrophage/ Dust Cells.
           a] These are nomadic phagocytes of the lungs.
       3) Deep to the alveolar wall is a thin layer of elastic c.t. and the
       basement membrane.
       4) The alveolus is in close association with a capillary bed.
           a] The capillary wall is flush up against the alveolar wall forming
   the Alveolar Capillary Membrane/Respiratory Membrane.
               1] It is very thin to provide as little of a barrier to diffusion
           as possible being 0.5 micrometers thick.
               2] It consists of:
                    a} alveolar wall of simple squamous epithelium
                    b} alveolar basement membrane
                    c} capillary basement membrane
                    d} endothelial wall of capillary.



                             C. Air Volumes Exchanged
1. In clinical terms a respiration means one inspiration (inhalation) And
    one expiration ( exhalation).
    a) We average 14 to 18 respirations per minute when at rest.
                                           115
2. Tidal Volume - the amount of air to pass through the lungs in one
    normal respiration.
    a) averages 500 ml
         1) Only 350 ml reach the alveoli.
             a] The remaining 150 ml remain in the dead spaces of the nose,
             pharynx, larynx, trachea, bronchi, and bronchioles.
                 1] It is known as :dead air”
3. Inspiratory Reserve Volume - the maximum amount of air which can
    enter the lungs.
    a) averages 3,100 ml above the 500 ml tidal volume
4. Expiratory Reserve Volume - the maximum amount of air which can be
    expired from the lungs.
    a) averages 1,200 ml above the 500 ml tidal volume
5. Residual Volume - the volume of air which always remains in the lungs               after
expiration.
    a) Some air will always remain in the noncollapsible airways and
    alveoli.
    b) averages 1,200 ml
6. Vital Capacity - is the sum of IRV + ERV + TV.
    a) averages 4800 ml
    b) It allows for increased breathing under stress.
7. Total Lung Capacity - is the sum of all the volumes (IRV + ERV + TV+RV)
    a) averages 6,000 ml


                          D. Nervous Control of Respiration
1. Respiration is controlled by several mechanisms designed to maintain
   homeostasis.                                                    {p. 622 f. 21.15}
   a) Inspiration and expiration depend on a pressure differential.
        1) When inhaling, the atmospheric pressure within the lungs is less
   than the pressure in the environment and so air will enter the
   lungs.
            a} To decrease pressure within the lungs the respiratory muscles
            expand the pleural cavities.
                1} The diaphragm contracts pulling the lungs down.
                2} The external intercostals pull the ribs up so as to expand
            the ribcage.
        2) When exhaling, the atmospheric pressure is greater in the lungs
   than in the surrounding environment so air will exit the lungs.
            a} To increase pressure in the lungs the respiratory muscles
            decrease the pleural cavities.
                1} The diaphragm relaxes “pushing” the lungs back up.
                2} The external intercostals relax allowing the ribs to lower.
                3} In cases of strong expiration the internal intercostals will
            push the ribs down further further reducing lung volume.
2. The respiratory muscles are controlled by the brain.
   a) The Respiratory Center of the brain is located within the brain stem.
   1) It is divided into three areas:
            a] Medullary Rythmicity Center.- is located within the reticular
        formation of the medulla oblongata.
                1] It has both an inspiratory and expiratory center.
                2] It controls the basic rhythm of breathing.
                                               116
        b] Apneustic Area - is located within the pons.
            1] It can modify the signal coming from the medullary
        rythmicity center.
        c] Pneumotaxic Area - is located within the pons.
            1] It can also modify the signal coming from the medullary
            rythmicity center.
    2) The respiratory center also has connections with the cerebral
    cortex which allows for some voluntary control over breathing
rate.
        a] However, we have involuntary, fail safe mechanisms which will
    force us to breath even if we have “held” our breath for some
        time.
            1] These are pH receptors on some of the major arteries (ex;
            aorta, carotids) which monitor carbon dioxide levels.
                 {p. 624 f. 21.16}




                                       117
                    CHAPTER 22: THE DIGESTIVE SYSTEM

                                     A. Introduction
1. The process of digestion involves five basic activities designed to
   prepare food for consumption by the cells:
   a) ingestion
   b) peristalsis
   c) mechanical and chemical digestion
   d) absorption
   e) defecation.
2. The organs of the digestive system can be divided up into two groups:
   a) Gastrointestinal Tract/Alimentary Canal                      {p. 634, f 22.1}
       1) The G I tract is a continuous tube running from the mouth to the
   anus through the ventral body cavities.
           a] Its total length is 9 m/30 ft.
       2) The organs of the G I tract include: mouth, pharynx, esophagus,
   stomach, small intestine, and large intestine.
   b) Accessory Organs
       1) Typically the accessory organs lay outside of the G I tract and
   release their products into the G I tract through ducts.
           a] They aid the G I tract in digestion.
           b] The exceptions are the tongue, gastric glands, and intestinal
       glands.
       2) The accessory organs include: teeth, tongue, salivary glands,
       pancreas, liver, gall bladder, and the intrinsic glands of the G I
       organs.
3. General Histology of the Digestive Tube                         {p. 639, f 22.6}
   a) The walls of the alimentary canal, from esophagus to anus, have the
   same basic tissue arrangement of four tunics:
       1) Tunica Mucosa or Mucosa
           a] The tunica mucosa is a mucus membrane attached to a muscular
           layer lining the lumen of the digestive tube.
               1] It is the innermost layer.
           b] There are three layers:
               1] The epithelium of the mucus membrane.
                    a} It is a simple columnar epithelium along the bulk of the
                    tube for secretion and absorption.
                    b} It is stratified squamous in the esophagus and anal canal
                    for secretion and protection.
               2] The connective tissue of the mucus membrane is an areolar
               c.t. called the Lamina Propria.
                    a} It will contain numerous blood vessels, lymph vessels,
               lymph nodes, lymphoid cells, and epithelial glands which
               have invaginated from the epithelium.
                    b} The lamina propria serves to support the epithelium, to
                    provide it with a blood supply, and to bind it to the
               underlying muscular layer.
               3] The Muscularis Mucosa is a smooth muscle sheet beneath the
               mucus membrane of the mucosa.
                    a} It throws the mucus membrane of the G I tube into folds
                                               118
                    so as to increase its surface area.
       2) Tunica Submucosa
           a] This is a loose connective tissue tunic which binds the tunica
       mucosa to the tunica muscularis.
           b] It is highly vascularized.
           c] It contains a nerve plexus which provides the ANS supply of the
           muscularis mucosa.
                1] The nerve plexus is the Submucosal/Meissner’s Plexus.
       3) Tunica Muscularis/Muscularis Externa
           a] In most of the G I tract it is two layers of smooth muscle.
                1] a} The inner layer/sheet is circularly arranged.
                    b} The outer layer is longitudinally arranged.
                2] Between the two layers is the Myenteric Plexus/Plexus of
           Auerbach.
                    a} This plexus provides ANS control for the tunica muscularis.
                3] Recent studies have also inicated the presence of a
                “pacemaker” composed of smooth muscle located between
           the two sheets in certain portions of the GI tract.
           b] However . . . .
                1] in the upper third of the esophagus the tunica muscularis is
                skeletal muscle.
                2] in the stomach there are three layers of smooth muscle in
           the tunica muscularis.
       4) Tunica Serosa
           a] This is the outermost tunic.
           b] It is a serous membrane also known as the Visceral Peritoneum.
4. The Peritoneum                               {p. 637, f 22.5; p.665, f. 22.26}
   a) The peritoneum is the serous membrane of the abdominopelvic cavity.
       1) It has two portions:
           a] Parietal Peritoneum lining the walls of the abdominopelvic
           cavity.
           b] Visceral Peritoneum covers the organs of the abdominopelvic
           cavity themselves.
       2) Between the two is the Peritoneal Space into which they secrete
   Peritoneal Fluid.
   b) The visceral peritoneum has large folds which allow blood vessels
   and nerves to travel to the organs as well as serving to hold the
   organs in place. These folds are:
       1) Mesentary - an outward fold of the intestinal serosa that serves
   to attach the small intestine to the posterior abdominal wall.
       2) Mesocolon - an outgrowth of the colonic serosa that serves to
   bind the colon to the posterior abdominal wall.
       3) Falciform Ligament - a fold of the peritoneum which binds the
       liver to the liver and anterior abdominal wall.
       4) Greater Omentum - a four layered fold of the stomach’s serosa
   which hangs down over the front of the intestines.
           a] It passes up to the transverse colon, around which it wraps, and
       then extends to the posterior abdominal wall where it also attaches.
           b] It will be heavily invested with fat and so is sometimes called
       the “fatty apron”.
       5) Lesser Omentum - a two layered fold of the stomach’s serosa
   which attaches the stomach, and duodenum, to the liver.
                                           119
                                   B. The Oral Cavity
1. The mouth, or oral cavity is also known as the Buccal Cavity.
{p. 640, f 22.7}
    a) It is formed by the cheeks, lips, hard palate, soft palate, and tongue.
2. The Cheeks and Lips
    a) The Cheeks are muscular structures covered by skin externally and
         internally by a mucus membrane.
         1) The mucus membrane is the same one for the entire mouth,
         stratified squamous epithelium, nonkeratinized over lamina
    propria.
         2) The cheeks terminate anteriorly at the lips.
    b) The Labia
         1) The labia are the lips, the upper lip is the superior labia and the
    lower lip is the inferior labia.
         2) The labia are fleshy folds made up of two tissue types:
             a] The outside is skin.
             b] The inside is stratified squamous epithelium, nonkeratinized.
             c] The transition zone between these two tissue types is called
         the Vermilion or Red Margin.
                  1] It is colored by underlying blood vessels.
         3) The inner surface of each lip is attached to the gums/gingivae by
         a midline fold of the mucus membrane called the Labial Frenulum.
    c) The cheeks and lips serve to keep the food in the mouth during
    mastication.
    d) The space between the cheeks and lips and the teeth and gums is
    called the Vestibule.
    e) The Fauces is the opening between the oral cavity and the oropharynx.
         1) The Oral Cavity Proper then is the space running form the
         vestibule to the fauces.
3. The Hard and Soft Palate
    a) The Hard Palate is formed by the maxilla and palatine bones and are
    covered by stratified squamous epithelium, nonkeratinized sitting on a
    thin layer of c.t.
         1) It forms the anterior portion of the roof of the mouth.
    b) The Soft Palate forms the posterior portion of the roof of the mouth.
         1)It is a muscular partition between the oropharynx and nasopharynx.
         2) The Uvula hangs from the free border of the soft palate.
             a] On either side of the uvula are 2 muscular folds that run down
             the lateral side of the soft palate:
                  1] Palatoglossal Arch (or anterior pillar) is the anterior fold.
                  2] Palatopharyngeal Arch (or posterior pillar) is the posterior
             fold.
4. The Tongue
    a) The tongue and its associated muscles form the floor of the oral
    cavity.
         1) It is attached inferiorly to the hyoid bone and anteriorly to the
    gingivae and floor by the Lingual Frenulum (a fold of the mucus
    membrane).
    b) The tongue is a muscular organ covered by a mucus membrane.
         1) The mucus membrane has elevations called papillae on its upper
         surface and sides.
             a] The papillae contain the taste buds.
                                                 120
       2) It is divided medially by the Median Septum causing its many
       muscles to be paired.
           a] The Extrinsic Muscles of the Tongue
                1] They originate outside of the tongue and insert in it.
                2] They include: genioglossus, styloglossus, and palatoglossus.
                3] They serve to move the tongue from side to side and in and
                out.
                     a} These movements manuever food for chewing, shape the
                     food, and force the food towards the fauces for
                swallowing.
                4] The extrinsic muscles form the floor of the mouth.
           b] Intrinsic Muscles of the Tongue
                1] These muscles originate and insert in the tongue.
                2] They include: transversus linguae, verticalis linguae,
                longitudinalis superior, and longitudinalis inferior.
                3] They allow the tongue to change shape for speech and
                swallowing.
   c) Blood and Nerve Supply
       1) Blood Supply
           a] The lingual artery supplies the tongue.
           b] The veins of the tongue drain into the internal jugular.
       2) Nerve Supply
           a] Most of the muscles are innervated by CN 12.
           b] Taste is conveyed by CN 7 and CN 9.
5. The Salivary Glands                                             {p. 643, f 22.10}
   a) The salivary glands produce saliva.
       1) Saliva is continuously being secreted by these glands in and near
       the mouth.
       2) It serves to keep the mucus membrane moist and to assist in
       digestion
           a] It lubricates the food (called the Bolus) and initiates its
       chemical break down.
                1] Saliva production increases immediately prior to ingestion
           and during mastication.
       3) The Nature of Saliva
           a] Saliva is made up mostly of water.
                1] Water forms the medium for the digestion of food
                     (i.e.; hydrolysis)
           b] It also has the protein Mucin which, when combined with water,
           forms mucus.
                1] Mucus serves to lubricate the bolus.
           c] There are also chlorides which serve to activate salivary
           amylase.
           d] Salivary Amylase is the main digestive enzyme of the mouth.
                1] It breaks down carbohydrates (amylose) into the
                dissacharide maltose.
                     a} This hydrolytic reaction is the only chemical breakdown
                     occurring in the mouth.
                2] Salivary amylase works best at a neutral pH.
           e] Saliva will also contain bicarbonates to buffer it so as to
           maintain a fairly neutral pH (pH is between 6.35 and 6.85).
           f] There is some urea and uric acid since saliva plays a slight
           role in their excretion.
                                                121
           g] Saliva also contains the enzyme Lysozyme which breaks down
           bacteria ingested with food.
   b) There are intrinsic and extrinsic salivary glands.
       1) The intrinsic salivary glands are the Buccal Glands.
           a] These are numerous, small glands distributed through out the
           oral cavity.
           b] The buccal glands produce only small amounts of saliva.
       2) The extrinsic glands (or salivary glands proper) are located
       outside of the mouth and have ducts which release saliva into the
   mouth. They are:
           a] The Parotid Glands
               1] These are subdermal glands located superficial to the
               masseter immediately anterior to the pinna.
               2] The parotid has the Parotid/Stensen’s Duct which carries
           saliva into the mouth.
                    a} The parotid duct opens in the vestibule over the second
                    molar.
               3] Its secretion is a watery, serous like fluid that is rich in
               amylase.
           b] The Sublingual Glands
               1] The sublingual glands are located beneath the floor of the
           mouth, beneath the tongue.
               2] They secrete their products into the Sublingual Ducts/Ducts
               of Rivinus.
                    a} The sublingual ducts open up onto the floor of the mouth.
               3] Their product is a thick, mucus rich fluid with little
           enzyme content.
           c] The Submandibular/Submaxillary/Submental Glands
               1] The submandibular glands are located beneath the mandible
               in the posterior portion of the floor of the mouth.
               2] They secrete their products each by one Submandibular
               /Wharton’s Duct which opens into the oral cavity on the
           floor of the mouth just behind the central incisors.
               3] Their product is intermediate between the other two being
           high in amylase and mucus content.
6. The Teeth                                              {p. 644-45, f 22.11-12}      a) The
teeth, or dentes, are located in sockets of the alveolar processes              of the
mandible and maxilla.
       1) These alveolar processes are covered by the gums, or Gingivae,
       which extend slightly into each socket to form the Gingival Sulcus.
       2) The teeth are attached within the sockets by the Periodontal
       Ligaments (this is a gomphosis joint).
   b) The Structure of the Tooth
       1) The typical tooth has three principle portions:
           a] Crown - the expanded portion above the level of the gingivae.
           b] Root - the tapered portion embedded within the socket.
               1] It will have between one to three projections.
           c] Cervix - the narrow portion between the crown and root.

      2) Composition
         a] The tooth is composed primarily of a bone like material called
         Dentin.
             1] Dentin encloses a cavity in the tooth.
                                           122
                    a} The enlarged portion of this cavity is called the Pulp
                    Cavity and it is located in the crown of the tooth.
                        1} It contains “pulp” a loose connective tissue containing
                    blood vessels, lymph vessels, and nerves.
                    b} The Root Canals are narrow extensions of the pulp cavity
                    within each root projection.
                        1} Each root has an opening at its base called the Apical
                        Foramen that allows for the passage of nerves, blood
                    vessels, and lymph vessels.
           b] The dentin of the crown is covered by Enamel.
               1] Enamel is the hardest substance in the body.
               2] It is a bone like material composed primarily of
                    calcium phosphate and calcium carbonate.
               3] It protects the tooth from wear.
           c] The dentin of the root is covered by Cementum which attaches
               the root o the periodontal ligament.
   c) The Types of Teeth in the Adult Dentition
       1) Incisors - (4 on each jaw) chisel like teeth used for cutting into
   food.
       2) Canines - (2 on each jaw) sharp teeth used for tearing food.
       3) Premolars - (4 on each jaw) teeth that serve to crush food.
       4) Molars - (6 on each jaw) teeth that serve to grind/crush food.


                           C The Pharynx and Esophagus
1. The Pharynx
   a) The pharynx is a common passageway connecting the mouth, nose,
   esophagus, and trachea.
   b) The bolus is swallowed (Deglutition) and enters the oropharynx.
       1) During deglutition the respiratory passageways close.
            a] The epiglottis covers the glottis.
            b] The soft palate moves posteriorly sealing the nasopharynx.
       2) The bolus passes from the oropharynx to the laryngeopharynx and
       then into the esophagus.
2. The Esophagus                                                       {p. 647, f 22.13}
   a) General
       1) The esophagus is a collapsible muscular tube of 25 cm (10”) in
   length.
       2) It is located immediately posterior to the trachea.
       3) It serves to connect the pharynx and the stomach.
       4) It is the beginning of the “Digestive Tube Proper”.
   b) Modifications to Its Tunics
       1) The Tunica mucosa has a stratified squamous, nonkeratinized
       epithelium.
       2) The tunica muscularis has skeletal muscle in the upper third of
   the esophagus.
       3) The outermost tunic is not covered by peritoneum along the bulk
       of its length since it is located outside of the abdominopelvic
   cavity.
            a] The portion inferior to the diaphragm, a short segment
       connecting to the stomach, is covered by peritoneum so it is
   called the Tunica Serosa.
                                               123
           b] The portion superior to the diaphragm is covered by loose
           connective tissue and is called the Tunica Adventitia.
   c) Functions of the Esophagus
       1) The esophagus does not secrete digestive enzymes.
           a] All of the chemical digestion occurring in the esophagus is due
           to the saliva which was swallowed with the bolus.
       2) There is some mucus secretion.
       3) The esophagus moves the bolus down its length through peristalsis
       due to contractions of the tunica muscularis.
           a] These muscular contractions will also play a slight role in
           mechanical digestion.
   d) At the point where the esophagus meets the stomach there is a
       circular band of muscle called the Gastroesophageal Sphincter.
       1) It is also known as the Cardiac or Lower Esophageal Sphincter.
       2) It protects the esophagus from acids and enzymes in the stomach.


                                      D. The Stomach
1. The stomach is an enlargement of the G.I. tract that is continuous with
   the esophagus and duodenum.                                              {p. 648, f 22.14}
   a) It is bordered by two sphincters, the cardiac and pyloric.
2. Anatomy
   a) Surface Anatomy
        1) The stomach is divided into four areas:
            a] Cardia - it surrounds the cardiac sphincter and receives food
        from the esophagus.
            b] Fundus - a dome shaped region above and to the left of the
            cardiac region.
            c] Body - the large, central portion of the stomach.
            d] Pylorus - the narrow region of the stomach where the stomach
            communicates with the duodenum.
                1] It has the Pyloric Sphincter.
        2) The curvatures of the stomach:
            a] Greater Curvature - the convex lateral border.
            b] Lesser Curvature - the concave medial border.
   b) The Tunics of the Stomach
        1) Tunica Mucosa                                                    {p. 649, f 22.15}
            a] When the stomach is empty the tunica mucosa lays in folds called
        Rugae.
                1] As the stomach fills and distends the rugae disappear.
            b] Microscopically the mucosa has a layer of simple columnar
            epithelium which invaginates into the underlying lamina propria at
            many points.
                1] These points form pits called the Gastric Pits. They are
            also known as Gastric Glands since they are composed of
            three different secretory cell types whose secretions are
        collectively called Gastric Juice.:
                     a} Chief Cells/Zymogenic Cells - secrete the principle
                     gastric enzyme, Pepsin.
                        1} Pepsin is a protease which breaks down proteins onto
                        peptide subunits.
                            (a) Pepsin is stored in its inactive form called
                                                124
                           Pepsinogen.
                    b} .Parietal Cells - secrete hydrochloric acid and gastric
                    intrinsic factor.
                        1} HCl provides an acidic environment for the stomach.
                           (a) The pH will be 1.8.
                           (b) This helps in the break down of food.
                           (c) The acidic environment activates pepsin which
                           requires a pH of about 2 to function well.
                        2} Gastric intrinsic factor assists in the absorption of
                    vitamin B12.
                    c} Mucus Cells - secretes mucus.
                        1} Mucus coats and protects the stomach from its own
                        enzymes and HCl.
       2) Tunica Submucosa - the standard
       3) Tunica Muscularis
           a] Unlike other organs of the G.I. tube the stomach has three
           sheets of smooth muscle making up its tunica muscularis.
               1] The three layers are:
                    a} outer longitudinal layer
                    b} middle circular layer
                    c} inner oblique layer
           b] The fiber arrangement of the three layers allows for the
               stomach to churn the food and cause mechanical digestion
           (called Maceration).
       4) Tunica Serosa
           a] This layer of visceral peritoneum has two outpocketings: the
       greater omentum and the lesser omentum.
3. Actions
   a) Several minutes after the bolus has entered the stomach, gentle,
   rippling peristaltic waves called Mixing Waves begin to macerate the
   food, mix it with the gastric juices, and reduce it to a thin liquid
   called Chyme.
       1) This mixing occurs primarily in the body.
           a] The fundus does not have mixing since it serves to store food.
               1] It can store food for up to an hour.
   b) The principle chemical activity of the stomach is the breakdown of
   proteins into peptide subunits.
       1) This is facilitated by the enzyme pepsin.
           a] The stomach must be protected from its own pepsin.
               1] Pepsin is secreted in its inactive form, pepsinogen.
               2] When pesin has become activated, due to HCl, the mucosa is
               covered by a protective layer of mucus.
       2) Another gastric enzyme is Gastric Lipase.
           a] Gastric lipase serves to break down butterfat molecules found
           in milk.
           b] It works best at a pH of between 5 and 6 and so has a limited
           role in the adult stomach.
   c) As digestion proceeds, more active peristaltic waves begin at about
   the middle of the stomach to push the chyme towards the pyloric
   sphincter and the duodenum.
       1) The movement of chyme from the stomach into the duodenum is
           due to pressure gradient.
           a] When intragstric pressure is greater than intraduodenal
                                                125
          pressure chyme is pushed into the duodenum.
              1] The peristaltic waves are largely responsible for the
              greater intragastric pressure.
          b] As a result of the chyme entering the duodenum, the
          intraduodenal pressure will become greater than the
          intragastric pressure and the pyloric sphincter will close.
   d) The stomach walls are impermeable to most substances and so little
   absorption of digestive nutrients will occur in the stomach.
       1) Certain substances will cross, however, such as water, alcohol,salts,
   and certain drugs.


                E. The Accessory Organs of The Small Intestine
1. The Pancreas                                             {p. 664 f 22.14-25}
   a) The pancreas is an oblong glandular organ located posterior to the
   greater curvature of the stomach.
       1) It is divided into: head (near the duodenum), body, and tail.
       2) The pancreas is made up primarily of glandular epithelial cells.
           a]Some of these glandular epithelial cells are endocrine in nature.
                1] They are found in spherical clusters called the Islets of
                Langerhans.
                     a] The islets of Langerhans consists of a variety of
                     endocrine cells such as the alpha, beta, and delta cells.
                     b] The endocrine cell population is lower than is the second,
                the exocrine, population.
           b] Most of the glandular epithelial cells are exocrine in nature.
                1] They will be arranged into secretory units called an
           Acinus/Alveolus and so are called Acinar Cells.
                     {p. 591. f. 21.24}
                     a} They secrete a variety of substances collectively called
                     Pancreatic Juice which will aid in digestion of chyme in
                the small intestine.
       3) The pancreatic juice will exit the pancreas through a large, main
   duct called the Main Pancreatic Duct/Duct of Wirsung.
           {p. 652, f 22.16}
           a] Typically, the main pancreatic duct joins with the Common Bile
       Duct to form the Hepatopancreatic Ampulla/Ampulla of Vater.
                1] This common duct will enter into the duodenum and release
                the products of the liver and pancreas onto an elevation of
           the duodenal mucosa called the Duodenal Papillae.
           b] In some individuals there may also be a second duct which
           carries the products of the pancreas to the duodenum.
                1] This is called the Accessory Duct/Duct of Santorini.
                2] It enters into the duodenum on its own and opens up at a
           point about 2.5 cm above the duodenal papillae.
   b) Functions
       1) The acini secrete enzymes for the digestion of foods in the small
       intestine.
       2) The alpha and beta cells of the islets of Langerhans secrete
           hormones which help to regulate blood-glucose levels.
           a] The alpha cells produce glucagon which promotes the release of
       stored glucose back into the blood.
                                               126
           b] The beta cells produce insulin which promotes the storage of
           glucose and its removal from the blood.
2. The Liver                                              {p. 659-61, f 22.20-22}
   a) The liver is located under the diaphragm and covers a large portion of
   the upper quarter of the abdominal cavity.
       1) It weighs about 1.4 kg (4 lbs) in the average adult.
   b) Anatomy
       1) The liver is almost completely covered by the peritoneum.
           a] It is completely covered by dense connective tissue (which lays
       below the peritoneum).
       2) It is divided into lobes:
           a] The lobes are:
                1] There are two principle lobes:
                    a} Right Lobe
                    b} Left Lobe
                2] Associated with the right lobe are two minor lobes:
                    a} Inferior Quadrate Lobe
                    b} Posterior Quadrate Lobe
           b] Separating the right and left lobes is a fold of the visceral
           peritoneum called the Falciform Ligament.
                1] The falciform ligament extends from the underside of the
           diaphragm to the superior surface of the liver.
                2] On the free border of the falciform ligament is the Round
                Ligament/Ligamentum Teres.
                    a} It extends from the liver to the umbilicus.
                    b} The round ligament is a fibrous cord derived from the
                fetal umbilical cord.
       3) The lobes are divided into functional units called Lobules.
           a] Lobules are microscopic structures composed of cords/plates of
       Hepatocytes arranged in a radial pattern around a Central Vein.
           b] Between the cords of hepatocytes are Sinusoids which carry
       blood through the lobule.
                1] They have the phagocytic Kupffer cells which will destroy
           bacteria and senscent blood cells.
           c] The lobule is a hexagonal structure.
                1] At each corner is a Portal Triad.
                    a} The portal triad consists of : Hepatic Artery, Portal Vein,
                and Bile Duct.
       4) The liver receives a double supply of blood.
           a] It gets oxygenated blood from the hepatic artery.
           b] It gets nutrient rich blood from the Hepatic Portal Vein which
       carries blood from the capillary beds servicing the stomach,
   small intestine, and large intestine.
           c] Both the hepatic artery and hepatic portal vein bring blood to
       portal triads from where it enters into the sinusoids.
                1] The hepatic artery brings oxygen to the hepatocytes.
                2] The hepatic portal vein brings nutrients to be processed by
                the hepatocytes and screened by both the hepatocytes and
           Kupffer cells.
           d] In addition deoxygenated blood is drained from the liver by the
           Hepatic Vein.
                1] The central veins drain the deoxygenated blood from the
           sinusoids and carry it to the hepatic vein.
                                               127
       5) Bile is produced by the hepatocytes.
           a] The hepatocytes secrete the bile into tiny canals running
           between the cords called Bile Canaliculi.
           b] The bile canaliculi carry the bile towards the portal triad
           where it is received by the bile duct.
           c] The bile ducts drain into larger ducts which drain into the Right
       and Left Hepatic Ducts.
           d] The right and left hepatic ducts unite to form the Common
           Hepatic Duct.
           e] The common hepatic duct joins with the Cystic Duct from the
       gall bladder to form the Common Bile Duct.
           f] The common bile duct joins with the main pancreatic duct to
       form the hepatopancreatic ampulla which enters the duodenum.
   c) Activities of the Liver
       1) The liver assists in the manufacture of many of the plasma
       proteins such as prothrombin, fibrinogen, albumin, and heparin.
       2) The Kupffer cells phagocytize bacteria andsenscent blood cells.
       3) It breaks down poisons, or transforms them into less harmful
       substances, or stores them so as to protect the rest of the body.
       4) It collects newly absorbed nutrients.
       5) It stores glycogen, copper, iron, and the vitamins A, D, E, & K.
       6) It stores and produces fatty acids and amino acids.
       7) It manufactures bile salts which are used for the emulsification
   and digestion of fats.
3. The Gall Bladder                                                {p. 660, f 22.21}
   a) The gall bladder is a 7 to 10 cm long, pear shaped organ located in a
   fossa on the visceral surface of the liver.
   b) Internal Anatomy
       1) Internally it has a mucus membrane.
           a] This inner layer will be thrown into folds called rugae which
           allowthe gall bladder to distend and to fill with bile.
       2) Around the mucus membrane is a muscular layer made up of
           smooth muscle.
           a] The fibers of this muscle will contract under hormonal
       influence to force bile out of the gall bladder.
       3) Around the muscular layer is a layer of connective tissue and an
   external covering of serosa.
   c) Functions
       1) The gall bladder stores and concentrates bile.
           a] Bile is being continually produced by the liver.
               1] It travels down the common bile duct.
                    a} When the stomach and small intestine are empty a
                    sphincter prevents the flow of bile into the
               hepatopancreatic ampullae. This is the Sphincter of Oddi.
                        1} So the bile backs up the cystic duct into the gall
                        bladder where it is stored.
                    b} When food is in the stomach and small intestine the
                    sphincter of Oddi opens and bile enters into the ampulla.
           b] The mucosa reabsorbs water from the stored bile concentrating
           it.


                                 F. The Small Intestine
                                         128
1. The small intestine is the site for the bulk of digestion and the
   absorption of nutrients.
   a) It runs from the pyloric sphincter to the Ileocolic Sphincter which
   guards the opening into the large intestine.
   b) The small intestine is the largest segment of the digestive tube
   being approximately 7 meters in length.
        1) It is divided into three segments: Duodenum, Jejunum, and Ileum.
2. The Tunics of The Small Intestine                        {p. 653, f 22.17}
   a) The tunica mucosa and submucosa have been modified to increase
   surface area and thusly the effectiveness of the small intestine.
   1) The mucosa contains many pits called Intestinal Crypts/Crypts of
   Lieberkuhn.
             a] As is the case with the stomach, these crypts are lined by
             glandular epithelial cells which form the Intestinal Glands.
                 1] These columnar epithelial cells secrete the intestinal enzymes.
                 2] One of these glands invaginates down into the submucosa. It
                 is the Brunner’s Gland/Submucosal Gland.
                      a} Brunner’s glands secrete a very alkaline mucus which
                 protects the intestine from the acidic chyme and
                 stomach acids.
                 3] Some of the glandular epithelial cells are goblet cells which
                 also secrete mucus.
        2) The columnar epithelial cells lining the lumen possess numerous
        apical evaginations of the plasmallema called Microvilli which
        increase the absorptive surface area.
        3) the mucosa is arranged into a series of finger-like folds called
        Villi which also increase the absorptive surface area.
             a] They are quite numerous at ~4 to 5 million.
             b] Each villus contains capillaries and a Lacteal to pick up nutrients.
        4) The mucosa and submucosa are also arranged into crescentric
   folds called the Plicae Circularis.
             a] Along with increasing surface area they also serve in
             increasing absorption by forcing the chyme to spiral down the
        intestine increasing its contact with the walls of the organ.
   b) The walls of the small intestine are rich in lymphoid cells and these
   will form aggregates .
        1) Aggregates forming a single lymph node are called Solitary Lymph
        Nodes and then there are large aggregates of lymph nodes forming
        the Peyer’s Patches.
        2) These aggregates of lymphatic tissue protect the body from
        pathogens entering with the food.
             a] So they are more developed in the ileum where we find the
             Peyer’s patches.
   c) The tunica muscularis is the standard type.
   d) The tunica serosa has an outgrowth of the visceral peritoneum called
   mesentary.
3. Activities Occurring Within the Small Intestine
   a) Chemical Digestion
        1) The chemical digestion of carbohydrates, lipids, and proteins in
   the small intestine require secretions from the intestinal glands
   as well as contributions from accessory organs.
             a] The Secretions of the Liver
                                               129
            1] The liver secretes bile.
                a} Bile is composed of: water, bile salts, bile acids, a
                number of lipids, and two pigments.
                    1} The two pigments are biliverdin and bilirubin.
                        (a) Biliverdin gives bile its greenish color.
                        (b) The pigment bilirubin gets its color from degraded
                        erythrocytes.
                b} Bile has an alkaline pH at between 7.6 and 8.6.
                c} Bile, particularly the bile salt component, serves to
                emulsify fats to prepare them for the action of lipases.
        b] The Secretions of the Pancreas
            1] The exocrine secretions of the pancreas are many and varied.
        They are collectively called “pancreatic juice”.
                a} Pancreatic juice is composed of: water, some salts,
                sodium bicarbonate, and a variety of enzymes.
                b} Pancreatic juice is slightly alkaline in pH being between
                7.1 and 8.2.
                    1} the enzymes of pancreatic juice work best at this pH.
                c} The enzymes of pancreatic juice include:
                    1} Pancreatic Amylase which breaks down carbohydrates
                    which hadn’t been acted on by pancreatic amylase into
                    maltose.
                    2} Lipases to break down fats
                    3} Nucleases to break down nucleic acids
                    4} Proteases to break down proteins not fully hydrolyzed
                    by pepsin into peptides.
                        (a) These include trypsin and chymotrypsin.
        c] Secretions of the Intestinal Glands
            1] The various secretions of the intestinal glands are called
        “intestinal juice”.
                a} It has a slightly alkaline pH of approximately 7.6.
                b} Intestinal juice contains: water, mucus, and a variety of
                enzymes to complete the chemical break down of proteins,
                carbohydrates, lipids, and nucleic acids.
    2) When the chyme reaches the duodenum, carbohydrates and proteins
have only begun to be broken down and lipids and nucleic acids are
relatively untouched. Chemical digestion in the small intestine
proceeds as follows:
        a] Carbohydrate Degradation
            1] Pancreatic amylase finishes converting carbohydrates into
            maltose.
            2] Maltose is converted into two molecules of glucose by the
        enzyme maltase.
            3] Sucrose is hydrolyzed by the enzyme sucrase to produce one
            molecule of glucose and one molecule of fructose.
            4] Lactose is hydrolyzed by the enzyme lactase to produce one
            molecule of glucose and one molecule of fructose.
        b] Protein Degradation
            1] Trypsin and chymotrypsin degrade the remaining proteins into
            peptides.
            2] a} Carboxypeptidase reduce whole or partially digested
            proteins into amino acid subunits.
                b} Erepsin finishes the job by converting all remaining
                                             130
                   peptides into amino acids.
           c] Lipid Degradation
               1] Lipids are first acted on by the bile salts which emulsify
               them, weakening their bonds.
               2] The resulting fat droplets are acted upon by pancreatic
               lipase.
           d] Nucleic Acid Degradation
               1] Nucleases produced by both the pancreas and the intestinal
               glands break down DNA and RNA.
   b) Mechanical Digestion
       1) In the small intestine there are three distinct movements caused by
   the tunica muscularis which aid in mechanical digestion:
           a] Rythmic Segmentation which mixes the chyme.
           b] Pendular Movements which also mixes the chyme.
           c] Propulsive Peristalsis which moves the chyme through the
           intestine.
   c) Absorption
       1) The digestion of food serves to break up foods into molecules
       which are small enough to cross the intestinal epithelium and
       enter into capillaries or lacteals.
           a] These small molecules are: monosaccharides (glucose, fructose,
           and galactose), amino acids, glycerols, fatty acid chains, and
       glycerides.
       2) The small intestine accounts for 90% of all nutrient absorption in
   the G.I. tube.
           a] Most of the remaining 10% occurs in the large intestine.
   d) Any undigested substances pass through the ileocecal valve into the
   large intestine..


                                 G. The Large Intestine
1. Introduction                                                          {p. 655, f 22.18}
    a) The overall functions of the large intestine are the completion of
    nutrient absorption, manufacture of certain vitamins, formation and
    expulsion of the feces.
    b) The large intestine is named for its greater diameter (6.5 cm) not its
    length (1.5 m).
    c) It extends from the ileocecal valve to the anus.
    d) It is attached to the posterior abdominal wall by a fold of its serosa
    called the mesocolon.
    e) The large intestine is broken up into four principle regions: cecum,
    colon, rectum, and anal canal.
         1) The opening into the large intestine is guarded by the ileocolic
         valve which allows materials to pass from the small intestine
    into the large intestine.
         2) Immediately below the ileocolic valve is a blind pocket called the
    Cecum.
             a] Attached to the cecum is a lymphoid structure called the
             Vermiform Appendix.
                 1] The appendix is attached by a fold of its serosa called the
             Mesoappendix to the posterior abdominal wall and inferior
             ileum.
                                              131
       3) The open end of the cecum merges with the Colon.
            a] The colon is by far the largest segment of the large intestine
       and is divided into four regions in humans:
                1] Ascending Colon
                2] Transverse Colon
                3] Descending Colon
                4] Sigmoid Colon
            b] The colon has turns between its segments.
                1] Between the ascending and transverse colon is the Right
                Colic/Hepatic Flexure.
                2] Between the transverse and descending colon is the Left
            Colic/Splenic Flexure.
       4) The Rectum is 20 cm in length and stores the feces prior to their
   elimination.
            a] It is located anterior to the sacrum and coccyx.
       5) The Anal Canal is the final 2 to 3 cm of the large intestine.
            a] Its mucosa is arranged into longitudinal folds called Anal
            Columns/Columns of Morgani.
            b] The anal canal terminates at a circular band of skeletal muscle
            called the Anal Sphincter/Anus.
2. The Tunics of the Large Intestine                                 {p. 583, f. 21.19}
   a) Since far less nutrient absorption is occurring in the large intestine
   it walls lack many of the modifications found in the small intestine.
       1) It lacks villi, microvilli, and the plicae circularis.
       2) It does have goblet cells which increase in number closer to the
   anus.
   b) The greatest specialization is found in the longitudinal layer of the
   tunica muscularis.
       1) Instead of being a continuous sheet it is broken up into three flat
   bands called the Taeniae Coli.
            a] Each band runs most of the length of the large intestine.
            b] Tonic contractions of the taeniae coli organize the large
            intestine into pouch-like segments called Haustra.
3. Activities of the Large Intestine
   a) Mechanical Digestion
       1) Movements of the large intestine are initiated when substances
   enter the small intestine.
       2) the movements are:
            a] Haustral Churning
                1] This movement is unique only to the large intestine.
                2] It is the filling of the haustra and squeezing of its contents
            as matter is moved from one haustra to the next.
            b] Mass Peristalsis
                1] This movement is also unique to the large intestine.
                2] When food enters the stomach mass peristalsis is initiated.
                      a} It is strong peristaltic waves, beginning at about the
                      midcolon, which drives the contents towards the rectum.
            c] Peristalsis also occurs in the large intestine.
   b) Absorption
       1) The large intestine absorbs water.
            a] However, the small intestine absorbs more water making it a
       more important hydrostatic organ.
            b] Water absorption is greatest in the cecum and ascending colon.
                                                   132
    2) The large intestine also absorbs vitamin K. and some forms of
    vitamin B.
         a] Vitamin K is produced by bacteria native to the large intestine
         (E. coli).
             1] The bacteria ferment any undigested carbohydrates and
         release hydrogen gas, carbon dioxide, methane and vitamin K
c) Feces Formation and Elimination
    1) Feces chemically are composed of: water, inorganic salts, epithelial
    cells, bacteria, products of bacterial decomposition, and undigested
    food substances.
    2) Defecation
         a] Distension of the rectal walls stimulate pressure receptors to
    initiate the defecation reflex.
         b] Contraction of the muscles of the rectal wall shorten the
         rectum which increases pressure on the walls of the rectum and
         anal canal.
         c] The pressure along with voluntary contractions of the
    diaphragm and abdominal muscles force the anal sphincter to
    open and allows the feces to be expelled.




                                       133
                     CHAPTER 23: THE URINARY SYSTEM

                                     A. Introduction
1. The primary function of the urinary system is to assist in the
   maintenance of homeostasis by controlling the composition and volume               of
blood.
   a) This is done by removing and restoring selected amounts of water
   and solutes.
   b) The urinary system will excrete selected amounts of various wastes.
       1) Many wastes are produced as a result of metabolism.
           a] Ex; excess water, carbon dioxide and heat, and too many ions
           such as sodium, chloride, and hydrogen.
           b] Some of these wastes are toxic and must be removed for our
       own safety.
               1] Ex; ammonia and urea produced by protein catabolism.
2. The Components of the Urinary System                         {p. 676, f. 23.1}
   a) Two Kidneys, the principle organ of excretion, for the regulation of
   blood composition and volume and for the removal of wastes from
   the blood (in the form of Urine).
   b) Two Ureters to pass the urine from the kidney to the bladder.
   c) One Urinary Bladder for the storage of urine.
   d) One Urethra for the expulsion of urine into the internal environment.
3. The urinary system is the principle system for the removal of wastes               from
the body but other systems are involved in waste removal such as:
   a) Respiratory System removes excess water and carbon dioxide in the
   expirant.
   b) Digestive System removes undigested food substances and a variety
   of other compounds through defecation.
   c) Integument System removes water, salts, and slight amounts of
   nitrogenous wastes as sweat.




                                     B. The Kidneys
1. The kidneys are located retroperitoneal, behind the parietal peritoneum,
   between the levels of T12 and L3 on the posterior abdominal wall.
   {p. 677, f. 23.2}
2. External Anatomy                                               {p. 679, f. 23.3}
   a) The kidney has a convex lateral surface and a concave medial surface.
        1) On the medial surface, near the center of this concave border, is
   the Hilus where the ureter and renal vein exit and the renal artery
   enters the kidney.
           a] Immediately internal to the hilus is the Renal Sinus.
   b) Three layers of tissue surround the kidney:
        1) Renal Fascia - the outermost layer, this is a thin layer of fibrous
   c.t. that attaches the kidney to the posterior abdominal wall and
   to other adjacent structures.
        2) Adipose Capsule - the middle layer, this is a mass of adipose
                                             134
        tissue which serves to protect the kidney from mechanical trauma.
        3) Renal Capsule - the innermost layer, this is a smooth, transparent
        layer of fibrous c.t. continuous with the outer coating of the
    ureter and hilus.
            a] It also serves as a guard against trauma and also as a barrier to
                the spread of infection.
3. Internal Anatomy                                                   {p. 680, f. 23.4}
    a) Gross Anatomy - The kidney is divided into three layers/regions.
        1) The outermost layer is the Cortex.
            a] The cortex is divided into two subregions:
                1] The Cortical Zone which lays immediately below the capsule.
                     a} It is the outer portion.
                2] The Juxtamedullary Zone which lays against the second
                layer, the medulla.
                     a} It is the inner portion of the cortex.
            b] The cortex is a smooth textured region.
            c] The cortex will send extensions into the medulla called the
            Renal Columns.
        2) The middle layer is the Medulla.
            a] The medulla also is divided into two portions:
                1] The Outer Zone makes up the outer third of the medulla.
                2] The Inner Zone makes up the inner two thirds of the medulla.
            b] The medulla is broken up by the renal columns into 8 to 18
            striated, triangular regions called the Renal Pyramids or
        Medullary Pyramids.
                1] The striations are due to the presence of straight tubules
            and blood vessels.
                2] The base of each renal pyramid faces the cortex and the apex
            faces the renal pelvis.
                     a} The apices are called Renal Papillae.
                3] A Renal Lobe is defined as a renal pyramid and the two renal
                columns flanking it.
                4] Within the medulla and the cortex are the Nephrons the
                microscopic functional units of the kidneys.
        3) The inner layer is the Renal Pelvis/Renal Sinus.
            a] The pelvis has between 8 to 18 cup like structure draining each
            renal pyramid called Minor Calyces which receive urine from the
            medulla.
            b] The pelvis also has 2 or 3 larger cup like structures called the
                Major Calyces which drain the minor calyces.
            c] The major calyces drain into the ureter at the hilus of the
            kidney.
    b) The Nephrons                                                           {p. 680, f. 23.4}
        1) The nephron is the functional unit of the kidney and is composed
        of a Renal Tubule and its vascular component.
            a] It begins which a double walled structure located in the cortex.
                1] The component from the renal tubule is called the
                Glomerular Capsule/Bowman’s Capsule. It has two layers:
                     a] Its outer wall, called the Parietal Layer, is composed of
                     simple squamous epithelium.
                     b] Between the outer and inner wall is the Capsular Space or
                         Urinary Space.
                     c] Its inner wall, called the Visceral Layer, is composed of
                                                 135
             specialized epithelial cells called Podocytes.
        2] The glomerular capsule surrounds the vascular component
        called the Glomerular Capillaries. This is a special capillary
    bed.
             a] The capillaries are fenestrated and lack diaphragms.
             b] The capillary bed receives blood from an arteriole (the
        Afferent Arteriole) and has blood drained by a second
        arteriole (the Efferent Arteriole).
        3] The glomerular capsule and glomerular capillaries the
        starting portion of the nephron called the Glomerulus or
    Renal Corpuscle.
             a} The renal corpuscle serves as the starting point of urine
             formation.
                 1} It is where the blood is filtered to produce “precocial
                 urine”.
             b} The glomerular capillaries and the visceral layer of
             Bowman’s capsule are in close association forming the
        Filtration Membrane/Barrier also known as the
        Endothelial-Capillary Membrane. It is composed of:
                 {p. 683 f. 23.7}
                 1} the endothelium of the glomerular capillaries
                     (a) which filters blood based on the size of its fenestrae
                 2}a fused basement membrane formed from both epithelia
                     (a) The fused basement membrane filters the blood by
                     molecule size and by electrostatic charge.
                 3} the visceral layer of the glomerular capsule
                     (a) The podocytes have cytoplasmic extensions which
                     wrap around the glomerular capillaries.
                     (b) There are foot like, secondary extensions coming
                     off of the primary extensions called Pedicels.
                          (1) They interdigitate between adjacent podocytes
                          leaving little intervening space.
                               [a] This space is called the Filtration Slit and
                               filters the blood borne material based on size.
             c} The filtration membrane filters water and solutes in the
             blood.
                 1} Large molecules, such as certain plasma proteins and
                 formed elements, can not fit through the barrier and
             are not a normal component of urine.
                 2} The filtrate passes into the capsular space and then to
                 the rest of the nephron.
    b] The remainder of the nephron is involved in “fine tuning” the
urine through reabsorption of valuable materials and secretion
of more wastes into the urine.
        1] They dive down into the medulla and then loop back up into
        the cortex.
             a} This loop is called the Loop of Henle.
        2] The renal tubule component is:
             a} Proximal Convoluted Tubule
                 1} A thick walled segment where the bulk of reabsorption
                 will occur.
                     (a) It is lined by a simple cuboidal epithelium whose
                          cells are modified to maximize reabsorption:
                                             136
                                 (1) numerous microvilli on the apical surface
                                 (2) numerous mitochondria
                                 (3) well developed basal infoldings
                   b} Proximal Straight Tubule
                       1} It is lined primarily by a simple squamous epithelium
                       having the modifications of the pct cells but to a much
                       lesser degree.
                   c} Distal Straight Tubule
                       1} This tubule is lined by the same epithelium as is the pst
                       close to the loop of Henle but it then switches to
                       the same epithelium found in the dct in the ascending
                   limb of the loop of Henle.
                   d} Distal Convoluted Tubule
                       1} This is another thick walled segment located in the
                   cortex close to the renal corpuscle.
                            (a) It has an epithelium similar to the pct but not has
                            well developed in its modifications.
                            (b) It is located near to the glomerulus since it contains
                            a regulatory structure which will influence glomerular
                       filtration.
               3] Depending on the class of nephron the vascular component
                   will be made up of one or two capillary beds.
       2) There are two classes of nephrons: {p. 680, f. 23.4; p. 684, f. 23.8}
           a] Cortical Nephrons
               1] These nephrons have their glomeruli located in the cortical
               zone of the cortex.
               2] Their loops of Henle do not extend very far into the medulla
               because of their shorter length.
               3] They have only one capillary bed associated with the loop of
               Henle called the Peritubular capillary Bed.
           b] Juxtamedullary Nephrons
               1] These nephrons have their glomeruli located in the
               juxtamedullary zone of the cortex.
               2] They have a much longer loop of Henle which dips far into the
               medulla.
               3] They have two capillary beds associated with their loops of
               Henle, the peritubular capillary bed and the Vasa Recta.
               4] Their greater length coupled with the extra capillary bed
           allow these nephrons to perform the bulk of water
           reabsorption.
       3) The nephrons’ dct will drain into Collecting Tubules in the cortex
   which drain into the Collecting Ducts.                     {p. 680, f. 23.4}
           a] Collecting ducts are singular tubules which will travel through
       the medullary pyramid towards the apex.
           b] In the inner zone of the medulla the collecting ducts become
       the Papillary Ducts which are slightly thicker walled.
               1] The papillary ducts drain into the minor calyces.
                   a} At the apex of the pyramid is the Area Cribosa, a region
                   of the apex perforated by the terminal openings of the
               many papillary ducts within a renal pyramid.
4. Blood and Nerve Supply of the Kidney
   a) Due to their role of cleansing the blood, the kidneys are very well
   vascularized receiving 25% of the cardiac output.
                                                 137
       {p. 679, f. 23.3b; p. 684-5, f. 23.8}
       1) Arterial Supply
             a] The Right and Left Renal Arteries branch off of the abdominal
             aorta and enter into the hilus of the right and left kidney
       respectively.
             b] The renal artery will branch into the Segmental Arteries.
             c] The segmental arteries branch into the Lobar Arteries which
       carry the blood towards each renal lobe.
             d] The lobar arteries branch into the Interlobar Arteries which
       travel in the renal columns towards the bases of the renal
       pyramids.
             e] In the bases of the renal pyramids the interlobar arteries
             become the Arcuate Arteries which arch around the base of the
       renal pyramids.
             f] Branching off of the arcuate arteries will be numerous
       Interlobular Arteries.
             g] The interlobular arteries give rise to the Afferent Arterioles.
             h] The afferent arterioles give rise to the glomerular capillaries
       of the renal corpuscles which are drained by the Efferent
       Arterioles.
       2) Capillary Beds
             a]The Peritubular Capillary Bed arises from the Efferent arteriole.
             b] In the juxtamedullary nephrons the efferent arteriole will also
       give rise to a second capillary bed called the Vasa Recta.
       3) Venous Supply - they will typically run parallel to the same named
       arteries.
             a] Both capillary beds are drained by the Interlobular Veins.
             b] The interlobular veins will drain into the Arcuate Veins.
             c] The arcuate veins are drained by the Interlobar Veins.
             d] The interlobar veins drain into the Lobar Veins.
             e] In most individuals the lobar veins drain directly into the Renal
       Veins which drain the kidneys.
                 1] In some people between the lobar and renal veins are the
             Segmental Veins.
                 2] The renal veins are drained by the inferior vena cava.
   b) The nerve supply of the kidneys is derived from the Renal Plexus of
   the ANS.
       1) The ANS will play a role in regulating the rate of filtration by
       vasoconstriction and vasodilation of the afferent and efferent
   arterioles.
5. The Juxtaglomerular Apparatus                                           {p. 687, f. 23.10}
   a) The juxtaglomerular apparatus is a regulatory structure which effect                the
rate of filtration in the glomerulus.
       1) It is made up of two cell populations:
             a] Macula Densa - a group of specialized epithelial cells located in
             the wall of the dct immediately adjacent to the afferent
                 arteriole.
                 1] They are flattened cells having many granules.
             b] Juxtaglomerular cells - modified smooth muscle cells of the
       tunica media of the afferent arteriole.
                 1] They are adjacent to the macula densa of the dct.
                 2] Unlike typical smooth muscle cells they contain granules.
   b) Mechanism of Regulation
                                                138
      1) The macula densa monitors ion levels in the urine passing through
      the dct.
      2) When ion levels are low, the macula densa releases chemicals
      agents which travel to the afferent arteriole. These chemicals
   have two effects:
          a] They cause the smooth muscle of the afferent arteriole to
          vasodilate.
               1] this allows more blood to enter the glomerulus.
          b] They cause the juxtaglomerular cells to release renin.
               1] Renin will travel through the blood and come in contact with
          another blood borne agent called angiotensinogen.
                   a} Angiotensinogen will become activated by renin causing
                   the active form, angiotensin 1, to form.
                   b} Angiotensin 1 will travel through the glomerular
               capillaries and become converted into angiotensin 2.
               2] Angiotensin 2 will cause the efferent arteriole to
               vasoconstrict.
                   a} This causes blood to exit at a slower rate.
          c] The result is that more blood enters the glomerulus, less can
          get out, causing blood pressure to build up against the
          filtration membrane increasing the rate of filtration.


                                     C. The Ureters
1. Urine will travel from the renal pelvis into the ureters where it is
   carried by peristalsis into the bladder.
   a) Each of the two ureters is a continuation of the renal pelvis.
   b) They are about 30 cm in length.
   c) As they approach the bladder the ureters increase in thickness.
        1) The ureters will enter the bladder at the superior lateral angle of
   its base.
             a] The ureters lack anatomical valves but have functional valves.
                 1] When the bladder is full it will press back upon the ureters
                 preventing more urine from entering into the bladder.
                 2] Pressure in the bladder prevents urine from flowing
                 backwards into the ureters.
2. The ureter has three tunics.                       {p. 688, f. 23.11-12}
   a) Tunica Mucosa - the innermost coat.
        1) It is a mucus membrane composed of transitional epithelium
        sitting on areolar c.t.
        2) It secretes mucus to protect itself from the acidic nature of
        urine and also from some of the solutes present in urine.
   b) Tunica Muscularis - the middle and thickest tunic.
        1) Along most of its length the tunica muscularis is composed of
        two sheets of smooth muscle, one circular and one longitudinal.
        2) In the third of the ureter proximal to the bladder the tunica
   muscularis has three sheets of smooth muscle.
             a] They are arranged: longitudinal, circular, and longitudinal.
             b] This adds to the thickness of the ureter’s wall.
   c) Tunica Fibrosa - the outermost tunic.
        1) This is a layer of fibrous c.t continuous with the renal capsule.
                                             139
                                 D. The Urinary Bladder
1. The urinary bladder is a hollow, muscular organ which stores urine prior          to
micturition (urination).                              {p. 614, f. 22.13}
   a) It is located in the pelvic cavity posterior to the pubic symphysis.
   b) It is freely movable, to allow it to handle a large volume of urine,
   and held in place only by folds of the peritoneum.
        1) Its shape will depend on its level of distension.
2. Structure                                          {p. 689-90, f. 23.13-16}
   a) At the base of the bladder, internally, there is a triangular region
   called the Trigone.                                       {p. 614, f. 22.15}
        1) This an area of the bladder’s tunica mucosa which will be free of
   its customary folds.
            a] These folds are Rugae which serve to increase its
            stretchability.
        2) The apices of the triangle are the openings of the two ureters and
            the urethra.
   b) The urinary bladder has four tunics.
        1) Tunica Mucosa - the innermost tunic.
            a] It is transitional epithelium sitting on top of an areolar c.t.
                1] The transitional epithelium, coupled with the rugae, help it
            to stretch.
        2) Tunica Submucosa - the second tunic.
            a] This is a layer of dense c.t. that serves to bind the tunica
            mucosa to the muscularis.
        3) Tunica Muscularis - the third tunic
            a] It is composed of three sheets of smooth muscle (arranged:
        longitudinal, circular, and longitudinal) collectively called the
        Detrussor Band.
                1] At the urethtal opening fibers from the circular layer form
            the Internal Urinary Sphincter.
                     a} External to the internal sphincter is the External Urinary
                     Sphincter which is composed of skeletal muscle and under
                     voluntary control.
        4) Tunica Serosa - the outermost tunic.
            a] It is a covering of visceral peritoneum.


                                      E. The Urethra
1. The urethra is a small tube leading from the floor of the bladder to the
   external environment.
   a) In females the urethra lays posterior to the pubic symphysis and is
   embedded in the anterior vaginal wall.                   {p. 615, f. 22.15b}
       1) Its opening, the Urethral Orifice, is located between the clitoris
   and the vagina and will open into the urogenital vestibule.
       2) The urethra averages 3.8 cm/ 1.5 inches in women.
   b) In males the urethra also plays a reproductive role. {p. 615, f. 22.15a}
       1) It passes through an accessory sex organ, the prostate, through
   the urogenital diaphragm, and then enters into the penis.
       2) The urethral orifice is located at the distal end of the glans penis.
       3) The urethra will be longer in males averaging about 20 cm or 8”. 2. The tunics
                                              140
of the urethra also vary between the genders.
    a) Both have a Tunica Mucosa continuous with that of the bladder.
    b) Both have a Tunica Submucosa of dense c.t. rich in blood vessels.
    c) Only females, however, have a third tunic, a Tunica Muscularis,
    composed of a circular smooth muscle sheet.




                                         141
                  CHAPTER 24 THE REPRODUCTIVE SYSTEM

                          A. The Female Reproductive System
1. The female reproductive system consists of:                   {p. 714, f. 24.10}
   a) the two ovaries to produce ova
   b) the uterine tubes to transport the ova to the uterus
   c) The uterus which serves as the site of development of the offspring
   d) the vagina
   e) the vulva
   f) the mammary glands which serve to nourish the child
2. The Ovaries, The Female Gonads                                               {p. 714, f. 24.10}
   a) The ovaries are paired organs located in the upper pelvis cavity on
   either side of the uterus.
        1) The ovaries are maintained in position by a series of peritoneal
   folds called “ligaments”
            a] The Suspensory Ligaments .serve to suspend each ovary from
            the posterior abdominal wall
            b] The ovaries are attached by the Ovarian Ligament to the
            Mesovarium..
                1] The mesovarium is a peritoneal fold holding the uterus in
            place.
                     a] The mesovarium is also called the Broad Ligament.
   b) Each ovary has a Hilus where the ovarian blood vessels and nerves
   enter the organ.
   c) The Anatomy of the Ovary                                          {p. 716, f. 24.12}
        1) Germinal Epithelium forms the outermost covering of the ovary.
            a] It is a simple cuboidal epithelium covering the free surface of the
            ovary.
        2) The Tunica Albuginea is deep to the germinal epithelium.
            a] It is a capsule of collagenous c.t.
        3) Deep to the tunica albuginea is a region of c.t. called the Stroma.
            a] the stroma is broken up into a cortex and a medulla.
            b] The Medulla of the ovary is the inner zone.
                1] It is a loose, well vascularized c.t
            c] The Cortex forms the outer zone.
                1] It is composed of c.t and contains the Ovarian Follicles.
                     a} Ovarian follicles are the ova and their surrounding tissues.
                     The different follicles represent different states of
                development:
                          1} Primordial Follicles - these are the most immature
                     follicles.
                             (a) A women is born with all of her primordial
                             follicles
                                  (1) After puberty, every month a few of the
                                  primordial follicles will be stimulated by
                             hormones to undergo a series of changes leading
                             to a mature follicle and ovulation..
                          2} Primary Follicles
                          3} Secondary Follicles
                          4} Graafian Follicle - the mature follicle, its readyto ovulate
                                                   142
                         (a) At ovulation the ovum is released and the remaining
                         cells of the follicle form an endocrine structure, the
                      Corpus Luteum.
                      5} Atretic Follicles - the degenerating follicles that did not
                      ovulate.
   d) Functions
       1) The ovaries produce and release the ova, the female gamete.
       2) The corpus luteum of the ovary produces the female sex hormones
       progesterone and estrogen.
            a] These hormones control reproductive states and establish and
            maintain secondary sexual characteristics.
   e) Blood and Nerve Supply
       1) Blood Supply
            a] The ovaries are supplied with blood by the ovarian arteries.
            b] The ovaries are drained by the ovarian veins.
       2) Nerve Supply - The nerves of the ovaries terminate on the ovarian
       blood vessels and do not enter into the ovary.
            a] They include both sympathetic and parasympathetic nerves.
3. The Uterine Tubes/Fallopian Tubes/ Oviducts                              {p. 714, f. 24.10}
   a) The two oviducts extend from the ovaries to the uterus.
       1) They transport the ova from the ovaries to the uterus.
       2) They are 10 cm (4 inches) in length
       3) They are located in .folds of the broad ligaments (of the uterus).
   b) The oviducts are divided into four regions:
       1) Infundibulum - the funnel shaped opening of the oviduct.
            a] It receives the ovulated ovum from the ovary.
            b] To better facilitate the capture of the ovum it:
                1] is funnel shaped
                2] has finger like extensions called Fimbriae on the opening of
                the infundibulum
                3] has numerous cilia which beat to conduct the egg into the
            oviduct.
       2) Ampulla - the longest segment making up two thirds of the length
       of the oviduct.
            a] It is a wide segment and is often the site of fertilization.
       3) Isthmus - a short, narrow segment connecting to the uterus.
       4) Intrauterine Component - a very short segment of the oviduct
   which penetrates the wall of the uterus.
   c) The uterine tube has three tunics:
       1) Tunica Mucosa - the innermost tunic, it has an epithelium of
       ciliated columnar cells and secretory cells.
            a] The mucosa is thrown into a series of multilevel folds.
            b] It serves to move the ovum through the tube and to maintain
       and nourish the ovum/embryo.
       2) Tunica Muscularis - a middle tunic composed of two sheets of
       smooth muscle.
            a] Peristaltic contractions of the muscularis help to move the
       egg/embryo through the oviduct.
       3) Tunica Serosa - the outermost tunic, it is a layer of visceral
       peritoneum.
   d) The Functional Role of the Oviduct
       1) Once per month, typically, one ovum is released near the
   infundibulum.
                                               143
       2) The ovum is swept into the oviduct by ciliary beating.
       3) The ovum is transported through the oviduct by a combination of
       ciliary and muscular actions towards the uterus.
       4) If fertilization occurs it usually occurs in the ampulla.
            a] The resultant embryo will develop as it continues to travel
            through the oviduct and within 7 days a blastocyst enters the
       uterus.
            b} If fertilization does not occur, the ovum will disintegrate after
       about 24 to 48 hours.
   f) Blood and Nerve Supply
       1) Blood Supply
            a] The oviducts receive blood from branches of the uterine and
       ovarian arteries.
            b] The oviducts are drained by the uterine veins.
       2) The oviducts receive both sympathetic and parasympathetic
            innervation.
            a] The nerves arise from the hypogastric plexus and from the
       pelvic splanchnic nerves.
4. The Uterus                                                             {p. 714, f. 24.10}
   a) The uterus is the site of embryo implantation, fetal development, labor,
   and menstruation.
       1) the uterus is located between the urinary bladder and the rectum.
       2) Prior to the first pregnancy this pear shaped organ is 7.5 cm long,
       5 cm wide, and 2.5 cm thick.
   b) Anatomical Subdivision of Uterus
       1) Fundus - a dome shaped portion superior to the attachment of the
       oviducts
       2) Body- the major, tapering central portion.
       3) Uterine cavity- the lumen of the body.
       4) Cervix - the narrow inferior portion of the uterus which opens
       into the vagina.
       5) Cervical Canal - the lumen of the cervix.
       6) Isthmus - the constricted region between the body and cervix.
       7) Internal Os - the junction between the isthmus and the cervical
   canal.
       8) External Os - the junction between the vagina and the cervical
       canal.
   c) There are several structures, either peritoneal folds or fibromuscular
   cords, called “ligaments” which hold the uterus in place:
       1) Broad Ligaments/Mesovarians - a pair of double folds of the
       parietal peritoneum which attach the uterus to the pelvic wall.
            a] Uterine blood vessels and nerves travel to the uterus through
       the broad ligaments.
       2) Uterosacral Ligaments - a pair of peritoneal extensions which
       attach the uterus to the sacrum.
            a] they lay on either side of the rectum.
       3) Cardinal Ligaments/Lateral cervical Ligaments - a pair of
   fibromuscular cords which extend below the broad ligaments
   between the pelvic wall and the cervix and vagina.
            a] They contain smooth muscle.
            b] They are the principle ligaments for the maintenance of uterine
       position.
       4) Round Ligaments - bands of fibrous c.t. located between layers of
                                                144
    the broad ligaments.
        a] They extend from a point on the uterus just below the uterine
    tubes to the external genitalia.
d) There are three tunics making up the wall of the uterus:
    {p. 722, f. 24.18}
    1) Perimetrium/Serosa - the outermost tunic, it is composed of
    visceral peritoneum.
        a] Laterally it becomes the broad ligament.
        b] Anteriorly the visceral peritoneum is reflected over the urinary
    bladder forming a shallow pouch called the Vesicouterine
    Pouch.
        c] Posteriorly the visceral peritoneum is reflected over the rectum
        forming a very deep pouch called the Rectouterine Pouch.
            1] The rectouterine pouch is a noticeable landmark since it is
            the lowest point on the floor of the pelvis.
    2) Myometrium - the middle tunic and by far the thickest forming the
    bulk of the uterine wall
        a] The myometrium is composed of three layers of smooth muscle.
        b] It shows regional variation being thickest in the fundus and
        thinnest in the cervix.
            1] In the cervix much of the muscle has been replaced by
            fibrous c.t.
        c] Contractions of the myometrium expel the fetus from the womb.
    3) Endometrium - the innermost tunic, it is a variable layer under
hormonal influence.
        a] It is a mucus membrane that is well vascularized and
        glandularized.
        b] It is composed of two layers:
            1] Stratum Basalis - the permanent layer, it is the layer in
            contact with the myometrium.
                 a} It serves to regenerate the other layer.
            2] Stratum Functionalis - the layer in contact with the lumen.
                 a} It varies in thickness during the uterine cycle and serves
                 as the site of implantation.
                 b} It is lost as a portion of the menses during menstruation.
e) Blood and Nerve Supply
    1) Blood Supply
        a] Blood is supplied to the uterus by the uterine arteries which
    are branches of the internal iliac arteries.
            1] Branches of the uterine arteries, called arcuate arteries are
            arranged circularly in the myometrium.
            2] The arcuates give off the radial branches which penetrate
        deeply into the myometrium.
            3] Immediately before penetrating the endometrium the radial
            arteries give rise to two classes of arterioles:
                 a} Straight Arterioles - terminate in the stratum basalis
            and supplies it with the materials necessary to
            regenerate the stratum functionalis.
                 b} Spiral Arterioles - penetrate the stratum functionalis
            and is affected by the uterine cycle.
        b] The uterus is drained by the uterine veins.
    2) Nerve Supply
        a] The uterus receives both sympathetic and parasympathetic
                                              145
       nerve fibers.
           b] The nerves terminate on the uterine blood vessels.
           c] The nerves arise from the hypogastric and pelvic plexuses.
5. The Vagina                                                           {p. 714, f. 24.10}
   a) The vagina is a hollow muscular organ of about 10 cm in length.
       1) It makes up the lower portion of the birth canal.
           a] It also serves to act as a passageway for the menses and as a
           receptacle for the penis during coitus.
       2) the vagina is located between the bladder and rectum.
       3) A recess called the Fornix surrounds the vaginal attachment to
   the uterus. The fornix is divided into four portions of unequal depth:
           a] Dorsal Fornix - the deepest.
           b] There are two Lateral Fornices.
           c] Ventral Fornix the shallowest.
   b) The vagina has only two tunics:
       1) Tunica Mucosa - a mucus membrane lined with stratified
       squamous epithelium.
           a] The epithelium and underlying c.t. of the vagina is arranged into
       folds called rugae.
           b] The mucosa contains large amounts of glycogen.
               1] Glycogen will decompose in the vagina producing organic
               acids which keep the vaginal pH low
                    a}.The acidic pH retards bacterial growth.
                    b} Unfortunately, the low pH is also a problem for sperm.
                       1} That is why the semen is alkaline.
           c] The lamina propria of the vagina is well vascularized.
       2) Tunica Muscularis - composed of a longitudinally arranged sheet
       of smooth muscle.
           a] It is very elastic to accommodate stretching of the vagina.
   c) At the vaginal orifice there occurs a thin fold of vascularized mucus
   membrane which partially occludes the opening called the Hymen.
   d) Blood and Nerve Supply
       1) Blood Supply
           a] The arteries are derived from branches of the internal iliac
           such ass the vaginal artery.
           b] The veins of the vagina form the vaginal plexus which is drained
           by the internal iliac veins.
       2) The nerves of the vagina are derived from the uteropudendal plexus.
6. The External Genitalia/Vulva/Pudendum                         {p. 714, f. 24.10}
   a) Mons Pubis/Mons Veneris - an elevation of adipose tissue, situated
   over the pubic symphysis, covered by coarse pubic hair.
   b) From the mons pubis extend two folds of skin posteriorly and inferiorly.
   These form, the Labia Majora.
       1) The labia majora are composed of adipose tissue and epithelium
       rich in sebaceous and sudoriferous glands and covered by hair
       laterally.
   c) Between the labia majora are two folds of mucus membrane,
   continuous with the mucus membrane lining the vagina, called the
   Labia Minora.
   d) The labia minora enclose the Urogenital Vestibule/Vestibule into
   which both the urethra and vagina open.
       1) The vaginal orifice occupies the greater portion of the vestibule
   and is bordered by the hymen.
                                              146
       2) The urethral orifice is anterior to the vaginal orifice.
       3) There are some glands associated with the vestibule.
           a] Greater Vestibular Glands/Glands of Bartholini
               1] These glands are found on either side of the vaginal orifice
                    a} Their ducts open into a groove between the hymen and
                    labia minora.
               2] They produce a mucoid secretion which provides for
               lubrication during intercourse.
           b] Lesser Vestibular Gland/Glands of Skene
               1] These glands are located posterior and to either side of the
               urethral orifice.
               2] Their secretion is also mucoid in nature.
   e) At the anterior margin of the labia minora is a small erectile organ
   called the Clitoris.
       1) It will be covered by a Prepuce.
       2) The exposed portion of the clitoris is called the Glans.
7. The Mammary Glands                                                  {p. 726, f. 24.22
   a) The mammaries are paired glands located over each pectoralis major.
       1) They are attached to the pectoralis major by a layer of c.t.
   b) Internally, each mammary consists of 15 to 20 lobes separated by
   adipose tissue.
       1) The amount of adipose tissue determines the size of the breast.
           a] In women who are not pregnant/lactating adipose accounts for
           most of the mass of the breast.
       2) Each lobe has several lobules.
           a] The lobules contain c.t. and secretory acini/alveoli.
               1] The alveolar cells are the milk secreting cells.
           b] Between the lobules are strands of c.t. called the Suspensory
           Ligaments of Cooper.
               1] These ligaments support the breast.
               2] They run between the skin and the deep fascia.
       3) The alveoli secrete the milk into the Secondary Tubules which
       pass it on to the Mammary Ducts.
           a] As the mammary ducts approach the nipple they empty into a
           sinuses called the Ampullae.
               1] the ampullae store milk.
           b] The ampullae will be drained by the Lactiferous Ducts.
           c] The lactiferous ducts terminate in the nipple.
   c) The Areola is a pigmented area of skin around each nipple.
       1) It contains sebaceous glands.



                         B. The Male Reproductive System
1. The male reproductive system consists of:          {p. 702-3, f. 24.1-2}
   a) the two testes to manufacture sperm
   b) a number of ducts to store and transport the sperm
   c) accessory glands that contribute semen
   d) and several supporting structures such as the penis.
2. The Scrotum                                        {p. 702-3, f. 24.1-2}
   a) The scrotum is a cutaneous outpocketing the abdomen which holds
   the testes.
                                          147
        1) It consists of loose skin and superficial fascia.
            a] The scrotum is separated into two lateral portions by a median
            ridge called the Raphe.
        2) Internally the scrotum is divided into two sacs by a septum.
            a] Each scrotal sac contains one testis.
            b] The scrotal septum is composed of superficial fascia and the
        Dartos.
                 1] The dartos is a contractile tissue composed of bundles of
            smooth muscle.
                     a} The dartos is also found in the rest of the scrotum.
                     b} The dartos will cause the scrotum to wrinkle in response
                     to a decrease in ambient temperatures.
   b) Its purpose is to house the testes and to keep them at a temperature
   beneficial to spermatogenesis.
        1) The dartos plays a role in this.
        2) It is assisted by a skeletal muscle located in the scrotum called
   the Cremaster.
            a] The cremaster surrounds the testis and is a part of the
        spermatic cord.
            b] It will elevate the testes when ambient temperatures drop.
   c) Blood and Nerve Supply
        1) The arterial supply is from the internal iliac (i.e.; pudendal
        branch), inferior epigastric (i.e.; cremasteric branch), and the
        femoral arteries (i.e.; external pudendal branch).
        2) The veins of the scrotum are collectively referred to as the
            scrotal veins.
        3) The scrotal nerves branch off of the pudendal, posterior
   cutaneous, and ilioinguinal nerves
3. The Testes, The Male Gonads                               {p. 702-3, f. 24.1-2}
   a) The testes develop high in the embryo’s posterior abdominal wall and
   then, at about 32 weeks, they begin to descend into the scrotum.
        1) Full descent is accomplished “shortly” after birth.
   b) Structure
        1) The testes are covered by a dense layer of fibrous c.t. called the
   Tunica Albuginea.
        2) The tunica albuginea extends inward and divides the testis into
   Lobules.
            a] There are between 200 and 300 lobules per testis.
        3) Each lobule will contain between 1 and 3 highly coiled tubules called
        Seminiferous Tubules which are the site of spermatogenesis.
        {p. 704, f. 24.3;}
            a] The seminiferous tubules contain two classes of cells. One
            class are developing sperm cells.                       {p. 706, f. 24.4}
                 1] Spermatogonia are the most immature of the developing
            sperm cells.
                     a} They are located in the periphery of the seminiferous
                     tubule against the basement membrane.
                 2] Spermatogonia are stem cells which will undergo mitosis
                 giving rise to the next cell stage of sperm development, the
            Primary Spermatocytes.
                 3] Primary spermatocytes will undergo meiosis 1 and give rise
                 to the Secondary Spermatocytes.
                 4] Secondary spermatocytes undergo meiosis 2 and become the
                                                 148
            Spermatids.
                a} Spermatids are haploid cells located near the lumen of
                the seminiferous tubule.
                b} They are not physically mature yet.
            5] The spermatids undergo morphological changes which allow
            them to transport the haploid nucleus to the egg. The
            resulting mature sperm cells are called Spermatozoa/Sperm
        Cells.
                a} These tapered, flagellated cells are located near the
                lumen of the seminiferous tubules and enter into the duct
                system when mature.
        b] The second cell class of the seminiferous tubule is the Sertoli
        Cell.
            1] These are large cells making up the bulk of the seminiferous
            tubule wall.
                a} The developing sperm cells are located in invaginations
                of the Sertoli cells.
            2] They produce secretions which nourish the developing sperm.
    4) Between the seminiferous tubules are clusters of endocrine cells
        called the Interstitial Cells of Leydig/Interstitial Cells/Leydig
    Cells.
        a] These epithelial cells produce the male androgens, most
        notably testosterone.
c) Blood and Nerve Supply
    1) The testes receive blood from the testicular arteries.
        a] The testicular arteries branch off of the aorta immediately
    below the origin of the renal arteries.
    2) The testes are drained by the testicular veins.
        a] The right testicular vein will drain into the inferior vena cava.
        b} The left testicular vein drains into the left renal vein which
        then drains into the inferior vena cava.
    3) The testes are innervated by the testicular plexus.
        a} The testicular plexus is supplied by the spinal nerves T10 and
        T11 as well as by the vagus nerve.
d) The Products of the Testes
    1) Spermatozoa - the exocrine product of the testes.
        a] 300 million sperm are produced per day, on average.
        b] They can live for up to 48 hours in the female reproductive
        tract.
        c] Structure
            1] Head - contains the haploid nucleus and a slight amount of
            cytoplasm.
                a} It will be capped by the Acrosome which contains the
                enzyme Hyaluronidase.
                    1} Hyaluronidase facilitates penetration of the ovum.
            2] Midpiece/Middle Piece - a small connecting portion between
                the head and the tail.
                a} It is the base of the flagellum and a collar of numerous
                mitochondria to power it.
            3] Tail - the long flagellum which drives the sperm towards
            the ovum.
    2) Testosterone - the endocrine product of the testes.
        a] Testosterone is the primary male androgen. It has a number of
                                            149
               effects on the body:
               1] It controls the growth, development, and maintenance of the
               male sex organs.
               2] It stimulates bone growth, protein anabolism, sexual behavior,
               final maturation of the sperm, and the development of the
           male secondary sexual characteristics.
               3] It also stimulates the descent of the testes into the
           scrotum prior to birth.
4. The Ducts of the Male Reproductive System                    {p. 702-3, f. 24.1-2}
   a) The Ducts of the Testes
       1) When spermatozoa drop into the lumen of the seminiferous
       tubules they travel to the Straight Tubules.
       2) The straight tubules carry the sperm into a series of ducts in the
   testis called the Rete Testis which drain the lobules.
   b) The Epididymis
       1) The epididymides are coma shaped organs located on the posterior
       margin of each testis. They have two types of ducts:
           a] Efferent Ducts - several ducts which receive sperm from the
       rete testis.
           b] Ductus Epididymis - a highly coiled singular tubule which receives
           sperm from the efferent ducts and transports it to the next
       duct, the vas deferens.
               1] It is 7 m in length.
               2] The ductus epididymis is lined with pseudostratified
               ciliated columnar epithelium.
                    a} It also has a thick muscular tunic which pushes the sperm
                    out of the ductus epididymis, by peristalsis, during
               ejaculation.
       2) The epididymis is broken up into:
           a] Head - capping the superior edge of the testis.
               1] It contains the efferent ducts.
           b] Body - the bulk of the epididymis it is on the posterior margin
       of the testis.
           c] Tail- - on the inferior end of the testis it drains into the vas
       deferens. Both the body and tail contain the ductus epididymis.
       3) The epididymis serves to store and transport sperm.
           a] It is the site of sperm maturation.
           b] It can store sperm for up to one month.
   c) The Vas Deferens/Ductus Deferens
       1) The vas defrens carries sperm from the epididymis, through the
   inguinal canal,and into the pelvic cavity where it loops around the
   posterior urinary bladder.
       2) The terminal portion of the vas defrens is dilated and called the
   Ampulla.
           a] It lays along the posterior urinary bladder below the seminal
       vesicle..
           b] Its tunica mucosa is very folded causing some to label the
           ampulla as a separate organ.
       3) Fuctionally : The vas deferens stores sperm for up to several
       months and during ejaculation will propel sperm towards the
   urethra through peristaltic contractions.
       4) Histology: The vas deferens is lined by pseudostratified, ciliated
   columnar epithelium and has a tunica muscularis composed of
                                               150
   three thick sheets of smooth muscle.
       5) The vas deferens is sometimes confused with the Spermatic Cord.
           a] The spermatic cord is a composite structure made up of: vas
       deferens, testicular artery, testicular vein, and lymphatic
       vessel covered by fibrous c.t. on which sits the cremaster
       muscle.
           b]It enters the body wall through the inguinal canal. {p. 631, f. 23.}
   d) The Ejaculatory Duct
       1) The ejaculatory duct is formed by the union of the ampulla and the
       duct draining the seminal vesicle.
           a] The right and left ejaculatory ducts are located posterior to
       the bladder and will penetrate the prostate gland.
   e) The Urethra
       1) The urethra, in the male, serves as a common passageway for
       urine and sperm.
       2) This terminal portion of the duct system passes through the
       prostate, urogenital diaphragm, and penis to open at the
   urogenital orifice at the distal portion of the glans penis. It has
   three portions:
           a] Prostatic Urethra - the portion to pass through the prostate.
               1] It receives sperm from the ejaculatory ducts.
           b] Membranous Urethra - the portion to pass through the
       urogenital diaphragm, the floor of the pelvis.
           c] Penile/Spongy Urethra - the portion to pass through the penis.
5. The Accessory Sex Glands                                 {p. 702-3, f. 24.1-2}
   a) The accessory glands secrete the liquid portion of the ejaculate,
   semen.
       1) Seminal Vesicles/Coagulating Glands
           a] This pair of glands is located posterior to the bladder and above
           the ampullae.
           b] They are the first to secrete fluid into the male ducts.
               1] Their secretion is an alkaline, viscous fluid rich in fructose.
               2] It is secreted into the ejaculatory ducts.
               3] Their secretion makes up about 60% of the seminal fluid.
       2) Prostate Gland                                                   {p. 711, f. 24.9}
           a] This walnut sized singular gland is located immediately inferior to
           the bladder where it encircles the superior urethra.
           b] The prostate also secretes an alkaline fluid that makes up
           between 13 and 33% of the semen.
               1] It is secreted into the prostatic urethra.
           c] The prostate is also a very well vascularized organ.
               1] When a male becomes sexually aroused blood vessels in the
               prostate fill causing the prostate to engorge and cut off
           urine flow from the bladder.
                    a} This protects the sperm from the acidic urine.
       3) Bulbourethral Glands/Cowper’s Glands
           a] These are a pair of pea sized glands located at the bulb of the
           penis.
           b] Their secretion makes up only a small amount of the seminal
               fluid.
               1] It is released into the penile urethra.
               2] It is a viscous mucus which serves to lubricate the urethra.
   b) The Nature of Semen
                                               151
       1) Semen, or seminal fluid, is a mixture of the secretions of the
       accessory sex organs.
           a] Seminal fluid plus sperm make up the Ejaculate.
                1] The ejaculate averages a volume of between 2.5 to 6.0 ml
                and has between 50 million to 100 million spermatozoa per ml.
       2) Semen has a slightly alkaline pH of between 7.35 and 7.5.
       3) Semen provides the sperm with:
           a] a transportation medium
           b] nutrients
           c] alkalinity to buffer the acidic nature of the male urethra and
       the female reproductive tract
           d] factors which activate the sperm cells at ejaculation.
6. The Penis                                                       {p. 710, f. 24.8}
   a) The penis is the mammalian intromittant organ.
       1) Its function is to introduce the sperm into the vagina.
   b) Structure
       1) The penis has a slightly enlarged distal portion called the Glans..
           a] Covering the glans is a fold of skin called the Prepuce
                (aka; foreskin).
       2) Internally the penis is composed of three cylindrical masses of
       tissue bound together by fibrous connective tissue.
           a] The three cylindrical masses are very well vascularized and
           divided into two groups:
                1] The two dorsolateral masses are called the Corpora
                Cavernosa.
                2] The singular, midventral mass is called the Corpus
                Spongiosum and contains the spongy urethra.
           b] All three tissue masses are erectile and contain blood sinuses.
                1] During sexual arousal the arteries supplying the penis dilate
           and large quantities of blood enter the sinuses.
                    a} Expansion of these sinuses compress the veins preventing
                    most drainage and so blood is retained.
                       1} This will cause the erection.
                2] After ejaculation, the arteries constrict reducing blood
                flow.
                    a} This will relax the pressure on the veins allowing them
                to drain the sinuses.
                       1}This will cause the penis to return to the flaccid state.
   c) Blood and Nerve Supply
       1) The penis is richly vascularized.
           a] It is supplied with blood by the femoral and pudendal arteries.
           b] The veins of the penis drain into the femoral and pudendal
           veins.
       2) The penis is also richly innervated.
           a] Sensory nerves to the penis are branches of the pudendal and
           ilioinguinal nerves.
                1] The penis is has many receptors for touch, temperature,
           and pressure.
           b] The corpora of the penis have both sympathetic and
           parasympathetic innervation.
                1] Parasympathetic innervation causes the erection.
                2] Sympathetic innervation causes the ejaculation.
                                             152
                    CHAPTER 25 THE ENDOCRINE SYSTEM

                                      A. Introduction
1.The endocrine system is the body’s other control system.
   a) It affects the body’s activities by releasing Hormones, chemical
   messengers, into the blood.
   b) The endocrine and nervous systems’ activities are coordinated into a
        interlocking supersystem, the Neuroendocrine system.
        1) Certain portions of the nervous system stimulate or inhibit the
   secretion of the hormones by the endocrine system.
        2) Hormones, in turn, can stimulate or inhibit the flow of nerve
        impulses.
2. Endocrine glands are the “ductless glands” and secrete their products
   into the extracellular spaces.
   a) These secretions enter into the capillaries to be transported by the
   blood stream.
   b) The secretions/products of the endocrine glands are called the
        hormones.
        1) One thing that all of the hormones have in common is that they
   function to maintain homeostasis by altering the physiological
   activities of cells.
        2) A hormone may stimulate changes in specific cells or organs
        called Target Cells/Organs.
            a] Some hormones may directly affect the activities of all of the
        cells of the body.
3. The endocrine glands include: hypophysis, thyroid, parathyroids, adrenal
   glands, pancreas, gonads, pineal gland, and thymus.           {p. 744, f. 25.1}


                        B. The Hypophysis or Pituitary Gland
1.Introduction                                                    {p. 747-8, f. 25.3-5}
   a) The hormones of the pituitary regulate a wide array of bodily actions
   causing it to have the nickname “master gland”.
   b) It is located in the sella turcica of the sphenoid and is attached to
   the hypothalamus by a thin stalk like structure called the Infundibulum.
   c) The pituitary is divided structurally, functionally, and evolutionary
   into two distinctly different regions:
        1) Anterior Pituitary/Adenohypophysis - the anterior division .
            a] Embryologically it is derived from ectoderm from an
            invagination of pharyngeal epithelium called Rathke’s Pouch.
            b] The anterior pituitary contains many glandular epithelial cells.
                1] It can be called the true endocrine portion of the hypophysis.
            c] The adenohypophysis is connected to the hypophysis by a
                system of blood vessels.
        2) Posterior Pituitary/Neurohypophysis - the posterior division.
            a] Embryologically it is derived from ectoderm from an
            evagination of the hypothalamus.
            b] This division contains axons of specialized neurons whose
                                               153
           perikarya are located in the hypothalamus.
               1] These axons are supported by special neuroglial cells of the
               posterior pituitary called Pituicytes.
           c] The posterior pituitary is connected to the hypothalamus by
       nerve fibers.
       3) Between the anterior and posterior pituitary is a small, relatively
   avascular zone called the Pars Intermedia.
2. Adenohypophysis/Anterior Pituitary/Pars Distalis
   a) The adenohypophysis releases a wide range of hormones and so has a
   variety of effects on the body.
       1) The release of the hormones by the anterior pituitary are
   regulated by hypothalamic secretions called Regulatory Factors.
           a] The regulatory factors are a link between the nervous and
           endocrine systems.
           b] Two regulatory factors are produced by the hypothalamus for
       almost every anterior pituitary hormone.
               1] One regulatory factor will stimulate the release of the
               hormone and a second factor will inhibit its release.
           c] The regulatory factors are delivered to the anterior pituitary
           by a system of blood vessels.
               1] The blood supply to the adenohypophysis and infundibulum is
               derived from several Superior Hypophyseal Arteries which
           are branches off of the internal carotids and posterior
           communicating arteries.
               2] The superior hypophyseal arteries give rise to a network of
               capillaries called the Primary Plexus in the infundibulum
               near the inferior hypothalamus.
                   a} Regulatory factors enter the primary plexus from the
               hypothalamus.
               3] The primary plexus drains into the Hypophyseal Portal Veins
                   which pass through the infundibulum.
               4] The hypophyseal portal veins give rise to a second capillary
               bed called the Secondary Plexus located in the
           adenohypophysis.
                   a} The secondary plexus is where the regulatory factors can
                   come in contact with the endocrine cells of the anterior
               pituitary.
                   b} The secondary plexus will also receive the secretion of
                   these endocrine cells and carry these hormones to the
               Anterior Hypophyseal Veins for distribution throughout
                   the body.
   b) Based on histological properties, there are three types of endocrine
   cells in the anterior pituitary and they secrete seven different
   hormones:
       1) Acidophils - cells which react favorably to acid based stains.
       They produce:
           a] Somatropin/Human Growth Hormone (HGH) - controls growth.
           b] Prolactin (PR) - initiates milk production.
       2) Basophils - cells which react favorably to alkaline based stains.
   They produce:
           a] Thyroid Stimulating Hormone (TSH) - controls the thyroid.
               1] This is an example of a Tropic hormone, a hormone which
               affects the secretions of another endocrine organ.
                                               154
           b] Adrenocorticotropic Hormone (ACTH) - stimulates the adrenal
           cortex to release its hormones.
           c] Follicle Stimulating Hormone (FSH) -stimulates the gonads to
       produce gametes
           d] Luteinizing Hormone (LH) -.stimulates other sexual and
           reproductive activities.
           e] Melanocyte Stimulating Hormone (MSH) - involved with skin
           pigmentation.
       3) Chromaphobes - cells which react unfavorably to all stains.
           a] Their secretions are undetermined.
           b] They may be basophils or acidophils which have already
           released their products.
3. Neurohypophysis/Posterior Pituitary/Pars Nervosa
   a) Strictly speaking, the posterior pituitary is not an endocrine organ
   since it does not synthesize any hormones.
       1) The posterior pituitary consists of pituicytes and the the axons of
   neurosecretory cells.
           a] The cell bodies of these neurosecretory cells are located in the
           hypothalamus in two separate nuclei.
           b] The axons/fibers of these cells form the
           HypothalamicHypophyseal Tract.
               1] They terminate on capillaries in the posterir pituitary.
       2) The neurosecretory cells produce two hormones which are stored
       and released by the posterior pituitary:
           a] Oxytocin - stimulates uterine contractions during labor, the
           ejection of milk, and may be involved in the orgasm.
           b] Antidiuretic Hormone (ADH) - prevents excessive urine
           formation by increasing water reabsorption.
               11] It is inhibited by alcohol.
       3) Following their production, these two hormones are transported
       down the axons by a carrier protein called Neurophysin.
           a] The hormones are stored in the axon terminals of the
       neurosecretory cells.
           b] When the hypothalamus is properly stimulated it sends
           impulses over the neurosecretory cells which will cause the
       release of the hormones into the blood.


                                     B. The Thyroid
1. The thyroid is located immediately inferior to the larynx. {p. 753, f. 25.8}
   a) The Lateral Lobes of the thyroid are located on either side of the
   trachea and are connected by the Isthmus which crosses the anterior
   trachea.
       1) When present, the Pyramidal Lobe extends upwards from the
       isthmus along the anterior trachea.
2. As is typical for an endocrine organ, the thyroid is very well
   vascularized.
   a) The main blood supply comes from the superior thyroid artery (a
   branch of the external carotid) and the inferior thyroid artery (a
   branch of the left subclavian artery).
   b) The thyroid is drained by the superior and middle thyroid veins.
       1) They, in turn, are drained by the internal jugular veins.
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3. The thyroid gland parenchyma is composed of two distinct cell
   populations.
   a) Follicular Cells -endocrine cells arranged into hollow spheres called
   Follicles.
       1)They produce the Thyroid Hormones, Thyroxin and Triiodothyronine.
           a] Thyroxin is the major product of the thyroid.
               1] It controls metabolism, helps to regulate growth and
               development, and increases the reactivity of the nervous
           system.
       2) The hormones are secreted into the lumen of the follicle where
   they are stored as a colloidal mass called Thyroglobulin.
           a] When the thyroid is stimulated to release the thyroid hormones,
       by TSH, the cells recover the hormones from the lumen and
       transport them into the blood stream by pinocytosis.
   b) Parafollicular/C Cells - endocrine cells arranged into small clusters
   located around, but not a part of, the follicles.
       1) They secrete their products directly into the blood stream.
       2) The parafollicular cells produce Thyrocalcitonin/Calcitonin which
   inhibits bone resorption which decreases blood-calcium levels.


                                   C. The Parathyroid
1. The four parathyroid glands are embedded within the posterior portion
   of the lateral lobes (two per lobe) of the thyroid.  {p. 755, f. 25.9}
2. The parathyroids have two types of epithelial cells.
   a) Principal/Chief Cells - these are the most numerous of the two cell
       types.
       1) They produce Parathyroid Hormone (PTH) which increases blood
       calcium levels by increasing bone resorption and also lowers
       blood-phosphate levels.
   b) Oxyphil Cells - these cells are far less numerous and their function
   is still not known.
       1) They may secrete a reserve supply of PTH.
3. Blood and Nerve Supply
   a) The parathyroids are well vascularized.
       1) They receive blood from branches of the superior and inferior
       thyroid arteries.
       2) They are drained by the superior, middle, & inferior thyroid veins.
   b) Nervous supply comes from branches of the vagus and cervical
       sympathetic ganglia.


                                 D. The Adrenal Glands
1. Introduction                                                      {p. 756, f. 25.10}
    a) The adrenal glands are a pair of glands located superior to each
    kidney which is why they are also called the “suprarenals”.
        1) They are embedded in the same adipose capsule.

   b) Structure
       1) The adrenal glands each have a capsule of fibrous c.t.
           a] Laying below this fibrous capsule is a thick layer of fatty c.t.
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       2) The parenchyma of the adrenal gland is divided both functionally
       and embryologically into two regions:
           a] Adrenal Cortex - the outer region.
                1] It is derived from mesoderm and secretes a variety of
                hormones.
           b] Adrenal Medulla - the inner region.
                1] It is derived from ectoderm and acts more like a
                sympathetic ganglion than like the typical endocrine organ.
   c) Blood and Nerve Supply
       1) The adrenal glands are among the body’s most vascularized organs.
           a] They receive blood from several suprarenal arteries.
           b] The blood is drained by the right and left suprarenal veins.
       2) The principal nerve supply is from preganglionic fibers which
       synapse with the secretory cells of the medulla.
           a] The preganglionic fibers arise from the splanchnic nerves and
           from the celiac and associated sympathetic plexuses.
2. The Adrenal Cortex
   a) The adrenal cortex forms the bulk of the adrenal gland and is divided
   into three zones:
       1) Zona Glomerulosa
           a] This is the outermost zone.
           b] It has its cells arranged into arched loops and ball shapes.
           c] Its primary secretions are a group of hormones called the
           Mineralcorticoids.
                1] Principal among these mineralcorticoids is the hormone
                Aldosterone which causes the kidneys to reabsorb sodium
           and to increase the excretion of potassium.
       2) Zona Fasciculata
           a] This is the middlet zone.
           b] It has its cells arranged into long, straight cords.
           c] Its primary secretions are a group of hormones called the
           Glucocorticoids.
                1] The glucocorticoids include Cortisone, Hydrocortisone, and
                Corticosterone which work together with other hormones to
                     reduce inflammation and to promote normal metabolism and
                to resist stress.
       1) Zona Reticularis
           a] This is the innermost zone.
           b] It has its cells arranged freely branching cords.
           c] It produces minute amounts of hormones.
                1] Principal among these is the sex hormones called
                Gonadocorticoids.
                     a] The chief gonadocorticoids secreted are the male
                     androgens.
3. The Adrenal Medulla
   a) The adrenal medulla contains many hormone secreting cells named
   Chromaffin Cells which surround large blood sinuses.
       1) These chromaffin cells develop from the same source as do
       sympathetic postganglionic cells.
       2) They are directly innervated by sympathetic preganglionic nerves.
           a] Their secretion of hormones is under direct ANS control.
   b) The adrenal medulla produces two sympathomimetic hormones called
   epinepherine and norepinepherine (at a ratio of 4 to 1).
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                                  E. The Pancreas
1. The pancreas is both an endocrine and an exocrine organ.
   {p. 758, f. 25.12}
   a) Its exocrine function is to produce various digestive enzymes to be
   delivered to the duodenum.
   b) The endocrine pancreas consists of clusters of endocrine cells,
   called Islets of Langerhans, amid the mainly exocrine cells of the
   parenchyma.
        1) The islets consist of 5 cell types, the 3 principal one being:
            a] Alpha Cells - secrete Glucagon which will stimulate the
            metabolism of glycogen so as to increase blood-glucose levels.
            b] Beta Cells - secrete Insulin which will stimulate the formation
   of glycogen so as to decrease blood-glucose levels.
            c] Delta Cells - secrete Somatostatin (HGHIF/Human Growth
            Hormone Inhibiting Factor) which will inhibit HGH secretion.
2. Blood and Nerve Supply
   a) Blood Supply
        1) The arterial supply of the pancreas is from the superior and
        inferior pancreaticoduodenal, the splenic, and the superior
   mesentaric arteries.
        2) The pancreas is drained by the superior and inferior
            pancreaticoduodenal, the splenic, and the superior mesentaric veins.
   b) The pancreas receives both sympathetic and parasympathetic nerves.
        1) Sympathetic nerves innervate the pancreatic blood vessels.
        2) Parasympathetic nerves innervate the glandular portion of the
   pancreas.



                                   G. The Gonads
1. The Testes
   a) The endocrine portion of the testes secrete the primary male sex
   hormone testosterone.
       1) Testosterone stimulates the development and maintenance of the
       male sexual characteristics.
2. The Ovaries
   a) The endocrine portion of the ovaries secrete the female sex hormones
       Progesterone and Estrogen.
       1) These hormones are responsible for development and maintenance
       of female sexual characteristics.
       2) Along with the gonadotropic hormones of the anterior pituitary
   these hormones regulate:
           a] the menstrual/uterine cylce
           b] maintenance of pregnancy
           c] preparation of the mammaries for lactation.


                            H. The Epiphysis Cerebrei
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1. The epiphysis cerebrei, or pineal gland, is a portion of the epithalamus          of the
diencephalon.
   a) It is attached to the roof of the third ventricle.
   b) It is the remains of a primitive vertebrate third eye.
   c) It has a capsule formed by the pia mater.
2. The parenchyma of the pineal gland is made up of two cell types.
   a) The two cell types are:
        1) Pinealocytes - the secretory cells of the pineal gland. They
        secrete the hormones:
            a] Melatonin - which may inhibit ovarian activities and so assist
        in the regulation of the menstrual cycle.
                 1] It is also involved in the circadian rhythms.
            b] Seratonin - important for normal brain physiology.
            c] Adrenoglomerulotropin - if it even exists this hormone may
        stimulate the adrenal cortex to produce aldosterone.
        2) Neuroglia as is typical for a portion of the CNS.
   b) Around the cells of the pineal gland can be observed preganglionic
   nerve fibers.
   c) At around puberty calcium deposits begin to accumulate in the pineal
   gland.
        1) These calcium deposits are called Corpora Arenacea, or “brain
   sand”.
        2) It is not clear if this progressive calcification is a sign of atrophy.

3. Blood Supply
   a) The epiphysis cerebrei receives blood from the posterior cerebral
   artery.
   b) It is drained by the great cerebral vein.



                                       I. The Thymus
1. The thymus is, typically, a bilobed structure located in the superior
   mediastinum posterior to the sternum and superior to the arch of the              aorta.
   a) The two lobes of the thymus are held together by an enveloping layer
   of connective tissue.
   b) The thymus reduces in size and functioning with the onset of puberty.
       1) Much of the parenchyma is replaced by fibrous c.t. and adipocytes.
2. Structure
   a) Each lobe is enclosed in a fibrous c.t. capsule.
       1) the capsule will extend into the lobe dividing it into lobules.
   b) Each lobule can be divided into a cortex and a medulla.
       1) The cortex, the outer portion, is composed almost entirely of
       tightly packed lymphocytes held in clusters by epithelioreticular
   tissue.
           a] This supportive epithelioreticular tissue is composed of reticular
           fibers and reticulocytes similar to, but of a different origin, than
   other reticulocytes in lymphoid tissues.
       2) The medulla consists mostly of epithelial cells and scattered
       lymphocytes.
           a) It will have a more cellular (than fibrous) reticulum.
           b) It will also have some epithelial cells arranged into concentric
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   layers called Thymic Corpuscles/Hassall’s Corpuscles.
3. The thymus functions in the immune response of the body.
   a) It serves as the site of T lymphocyte maturation.
   b) It produces the hormone Thymosin which will increase the production
   of plasma cells in response to an infection.
4. Blood and Nerve Supply
   a) Blood Supply
        1) The arterial supply is derived mainly from the internal thoracic
   and inferior thyroid arteries.
        2) The thymus is drained by the brachiocephalic, thyroid, and
        internal thoracic veins.
   b) The thymus receives both sympathetic and parasympathetic nerves.


                       J. Other Hormone Producing Tissues
1. Body tissues other than the multicellular endocrine glands also secrete
   hormones.
   a) The lamina propria of the gastrointestinal tract has numerous
   unicellular endocrine glands secreting a variety of hormones that
   regulate digestion in the stomach and in the small intestine such as:
        1) stomach gastrin
        2) intestinal gastrin
        3) pancreatic gastrin
        4) secretin
        5) pancreozymin (aka; cholecystokinin)
        6) enterocrinin
        7) enterogastrone
   b) The placenta is another endocrine structure, and endocrine tissue.
        It produces:
        1) human chorionic gonadotropic hormone (HCG)
        2) estrogen
        3) progesterone
        4) relaxin
2. The liver and kidneys, although not considered to be endocrine organs,
   may play a role in the endocrine system.
   a) They secrete an enzyme called Renal Erythropoietic Factor into the
   blood.
        1) Renal erythropoietic factor will travel through the blood where it
   will act upon certain plasma proteins to bring about the
   formation of Erythropoietin.
            a] Erythropoietin stimulates increased erythropoiesis.




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