Orientation to the Human Body

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Anatomy & Physiology I
Chapter 4
Histology - study of tissues
Tissue - a collection of similar cells that group together to
  perform a specialized function.

Tissue Classification
Four main groups of tissues
• Epithelial
• Connective
• Muscle
• Nervous tissue
Tissue Classification
      Nervous tissue: Internal communication
      • Brain, spinal cord, and nerves
      Muscle tissue: Contracts to cause movement
      • Muscles attached to bones (skeletal)
      • Muscles of heart (cardiac)
      • Muscles of walls of hollow organs (smooth)
      Epithelial tissue: Forms boundaries between different
      environments, protects, secretes, absorbs, filters
      • Skin surface (epidermis)
      • Lining of GI tract organs and other hollow organs
      Connective tissue: Supports, protects, binds
      other tissues together
      • Bones
      • Tendons
      • Fat and other soft padding tissue
Epithelial Tissue
   Forms a protective covering for the body
   Is the main tissue of outer layer of skin
   Forms membranes, ducts, and the lining of body
    cavities and hollow organs
   Layers of closely adhering cells
   Flat sheet with upper surface exposed to the
    environment or an internal body cavity
   No blood vessels - underlying connective tissue
    supplies oxygen
   Rests on basement membrane - anchors epithelium
    to connective tissue
Structure of Epithelial Tissue
Classification by shape
 Squamous – flat cells
 Cuboidal – cube shaped cells
 Columnar – tall, narrow cells

Classification by arrangement
 Simple – one layer of cells; all cell in contact with basement
 Stratified – two or more layers of cells
 Pseudostratified – one layer of cells but appears to be more
Simple vs. Stratified Epithelia
   Simple epithelium
    ◦ allows diffusion and secretion of materials
   Stratified epithelium
    ◦ protection in areas subject to wear and tear

    (a)   Classes of

                        Simple                       Stratified

    (b)   Cell

                       Squamous     Cuboidal         Columnar
Epithelial Tissue (Epithelium)
Two main types (by location):
  1. Covering and lining epithelia
       On external and internal surfaces

  2. Glandular epithelia
       Secretory tissue in glands
Overview of Epithelial Tissues
   For each of the following types of epithelia,
    ◦ Description
    ◦ Function
    ◦ Location
Simple Squamous Epithelium
Description: Single layer of flattened
cells with disc-shaped central nuclei
and sparse cytoplasm; the simplest
of the epithelia.

                                                                                                Air sacs of
Function: Allows passage of                                                                     lung tissue
materials by diffusion and filtration
                                                                                                Nuclei of
in sites where protection is not
important; secretes lubricating
substances in serosae.
Location: Kidney glomeruli; air sacs
of lungs; lining of heart, blood
vessels, and lymphatic vessels; lining
of ventral body cavity (serosae).

                                         Photomicrograph: Simple squamous epithelium
                                         forming part of the alveolar (air sac) walls (125x).
    Epithelia: Simple Squamous
   Two other locations
    ◦ Endothelium
      The lining of lymphatic vessels, blood vessels, and
    ◦ Mesothelium
      The epithelium of serous membranes in the ventral
       body cavity
Simple Cuboidal Epithelium
  Description: Single layer of
  cubelike cells with large,
  spherical central nuclei.

 Function: Secretion and

  Location: Kidney tubules;
  ducts and secretory portions
  of small glands; ovary surface.

                                    Photomicrograph: Simple cuboidal
                                    epithelium in kidney tubules (430x).
 Simple Columnar Epithelium
Description: Single layer of tall cells
with round to oval nuclei; some cells
bear cilia; layer may contain mucus-
secreting unicellular glands (goblet cells).

Function: Absorption; secretion of                                                           cell
mucus, enzymes, and other substances;
ciliated type propels mucus (or
reproductive cells) by ciliary action.
Location: Nonciliated type lines most of
the digestive tract (stomach to anal canal),
gallbladder, and excretory ducts of some
glands; ciliated variety lines small
bronchi, uterine tubes, and some regions                                                     Basement
of the uterus.                                                                               membrane

                                               Photomicrograph: Simple columnar epithelium
                                               of the stomach mucosa (860X).
Pseudostratified Columnar Epithelium
Description: Single layer of cells of
differing heights, some not reaching
the free surface; nuclei seen at                                                               Cilia
different levels; may contain mucus-                                                           Mucus of
secreting cells and bear cilia.                                                                mucous cell

 Function: Secretion, particularly of                                                          stratified
 mucus; propulsion of mucus by                                                                 epithelial
 ciliary action.                                                                               layer

Location: Nonciliated type in male’s
sperm-carrying ducts and ducts of
large glands; ciliated variety lines
the trachea, most of the upper
respiratory tract.
 Trachea                                Photomicrograph: Pseudostratified ciliated
                                        columnar epithelium lining the human trachea (570x).
Stratified Squamous Epithelium
Description: Thick membrane
composed of several cell layers;
basal cells are cuboidal or columnar
and metabolically active; surface
cells are flattened (squamous); in the
keratinized type, the surface cells are
full of keratin and dead; basal cells
are active in mitosis and produce the
cells of the more superficial layers.

Function: Protects underlying
tissues in areas subjected to abrasion.                                                     Nuclei
Location: Nonkeratinized type forms                                                         Basement
the moist linings of the esophagus,                                                         membrane
mouth, and vagina; keratinized variety
forms the epidermis of the skin, a dry
                                          Photomicrograph: Stratified squamous epithelium
                                          lining the esophagus (285x).
Stratified Epithelia
 Stratified epithelium is found in tissues subject to wear and
  tear; provides protection to underlying tissues; retards water
  loss through skin; resists penetration by pathogenic
 range from 2 to 20 or more layers of cells
 some cells resting directly on others; only the deepest layer
  attaches to the basement membrane
 three stratified epithelia are named for the shapes of their
  surface cells
 most widespread epithelium in the body
 deepest layers undergo continuous mitosis
    ◦ their daughter cells push toward the surface and become flatter as
      they migrate farther upward
    ◦ finally die and flake off – exfoliation or desquamation
Epithelia: Stratified Cuboidal
 Quite rare in body
 Found in some sweat and mammary
 Typically two cell layers thick
Epithelia: Stratified Columnar
 Limited distribution in body
 Small amounts in pharynx, male urethra,
  and lining some glandular ducts
 Also occurs at transition areas between
  two other types of epithelia
Transitional epithelium
Description: Resembles both
stratified squamous and stratified
cuboidal; basal cells cuboidal or
columnar; surface cells dome
shaped or squamouslike, depending
on degree of organ stretch.

Function: Stretches readily and
permits distension of urinary organ
by contained urine.
Location: Lines the ureters, urinary                                                               Basement
bladder, and part of the urethra.                                                                  membrane
                                       Photomicrograph: Transitional epithelium lining the urinary
                                       bladder, relaxed state (360X); note the bulbous, or rounded,
                                       appearance of the cells at the surface; these cells flatten and
                                       become elongated when the bladder is filled with urine.
    Glandular Epithelia

   A gland is an organ specialized to produce
    a substance for use elsewhere in the body
    or releases them for elimination from the
   Classified by:
    ◦ Site of product release—endocrine or exocrine
    ◦ Relative number of cells forming the gland—
      unicellular (e.g., goblet cells) or multicellular
Endocrine and Exocrine Glands
   Glands are composed of epithelial tissue in a connective
    tissue framework and capsule
   exocrine glands - maintain their contact with
    the body surface by way of a duct (epithelial tube
    that conveys secretion to surface)
    ◦ sweat, mammary and tear glands
   endocrine glands - lose their contact with the
    surface and have no ducts
    ◦ hormones – secretion of endocrine glands
    ◦ secrete (hormones) directly into blood
    ◦ thyroid, adrenal and pituitary glands
   some organs have both endocrine and exocrine
    function (liver, gonads, pancreas)
Exocrine Glands
 More numerous than endocrine glands
 Secrete products into ducts
 Secretions released onto body surfaces
  (skin) or into body cavities
 Examples:
    ◦   mucous glands
    ◦   sweat glands
    ◦   Oil glands
    ◦   salivary glands
Exocrine Glands
 Single     cell
 ◦ Goblet cell (secretes mucus)
      The only important unicellular gland is the goblet cell

 Multiple        cells
 ◦   Simple Tubular (found in intestine)
 ◦   Branched tubular (found in stomach)
 ◦   Coiled tubular (sweat glands)
 ◦   Saclike or alveolar (sebaceous glands)
 ◦   Compound (salivary glands)

Rough ER
Multicellular Exocrine Glands
 Multicellular exocrine glands are
  composed of a duct and a secretory unit
 Classified according to:
    ◦ Duct type (simple or compound)
    ◦ Structure of their secretory units (tubular,
      alveolar, or tubuloalveolar)
Types of Exocrine Glands
      Simple coiled tubular       Compound areolar              Compound tubuloareolar

      Example: Sweat gland
                                                                   Example: Pancreas
      Duct                      Example: Mammary gland

      Secretory unit

        simple - unbranched duct
        compound - branched duct
        shape of gland
         ◦ tubular – duct and secretory portion have uniform diameter
         ◦ alveolar - secretory cells form dilated sac (alveolar or sacklike )
         ◦ tubuloalveolar - both tubular and alveolar portions
Multicellular Exocrine Glands
               Simple duct structure                          Compound duct structure
               (duct does not branch)                         (duct branches)

            Simple tubular          Simple branched
            Example                 Example                            Compound tubular
            Intestinal glands       Stomach (gastric)                  Example
                                    glands                             Duodenal glands of small intestine

            Simple                  Simple branched
            alveolar                alveolar              Compound alveolar            Compound
            Example                 Example               Example                      tubuloalveolar
            No important            Sebaceous (oil)       Mammary glands               Example
            example in humans       glands                                             Salivary glands

               Surface epithelium      Duct     Secretory epithelium
Methods of Secretion Merocrine Gland
                                    merocrine glands (eccrine
                                     glands) – have vesicles that
                                     release their secretion by
                                     ◦ tear glands, pancreas, gastric
                                       glands, and others

                                    apocrine glands – primarily
                                     merocrine mode of secretion
                    Nucleus          ◦ axillary sweat glands, mammary

  Merocrine gland
Methods of Secretion Holocrine Gland

   holocrine glands – cells
    accumulate a product and then
    the entire cell disintegrates
    ◦ secretion a mixture of cell
      fragments and synthesized
    ◦ oil glands of scalp, glands of eyelids
                                               (b) Holocrine gland
Connective Tissue Characteristics
   cells usually occupy less space than the
    extracellular material
   most cells are not in direct contact with each
    ◦ separated by extracellular material
   highly vascular – richly supplied with blood
    vessels (except cartilage which is avascular)
   most abundant, widely distributed, and
    histologically variable of the primary tissues
Functions of Connective Tissue
 binding of organs – tendons and ligaments
 support – bones and cartilage
 protection – bones and blood
 movement – bones
 storage – fat, calcium, phosphorus
 transport - blood
Structural Elements of Connective
   Ground substance

    ◦ Medium through which solutes diffuse
      between blood capillaries and cells
    ◦ Components:
      Interstitial fluid
      Adhesive glycoproteins (―glue‖)
      Proteoglycans
Connective Tissue Fibers
   Collagen (white fibers)
    ◦ Strongest and most abundant type
    ◦ tough, flexible, and resist stretching
    ◦ tendons, ligaments, and deep layer of the skin are mostly
   Elastic (yellow fibers)
    ◦ Thinner than collagen fibers
    ◦ Allows stretch and recoil
   Reticular
    ◦ thin collagen fibers coated with glycoprotein
    ◦ form framework of such organs as spleen and lymph
Structural Elements of Connective
   Cells
    ◦ Immature, secretory cells = ―blasts‖
    ◦ Mature cells = ―cytes‖
       Fibroblasts – produce fibers and ground substances
       Chondroblasts and chondrocytes in cartilage
       Osteoblasts and osteocytes in bone
       Hematopoietic stem cells in bone marrow
       Adipocytes, leukocytes, mast cells, and
Cell types   Extracellular matrix
               Ground substance
Macrophage     Fibers
               • Collagen fiber
               • Elastic fiber
               • Reticular fiber

Fat cell       Capillary
Mast cell

Connective Tissue Categories
Categorized by physical properties
 Circulating connective tissue
    ◦ Blood
   Generalized (fibrous) connective tissue
    ◦ Loose: Areolar, Adipose and Reticular
    ◦ Dense: Regular, Irregular and Elastic
   Structural connective tissue
    ◦ Cartilage: Hyaline, Elastic, Fibrocartilage
    ◦ Osseous (Bone) Tissue
Description: Red and white
blood cells in a fluid matrix

Function: Transport of
respiratory gases, nutrients,                                                           Neutrophil
wastes, and other substances.

Location: Contained within
blood vessels.                                                                          Red blood


                                Photomicrograph: Smear of human blood (1860x); two
                                white blood cells (neutrophil in upper left and lymphocyte
                                in lower right) are seen surrounded by red blood cells.
Types of Generalized (Fibrous)
Connective Tissue
   loose connective tissue
    ◦ much gel-like ground substance
      between cells

    dense connective tissue
    ◦ fibers fill spaces between cells
Areolar (loose connective tissue)
Description: Gel-like matrix with all
three fiber types; cells: fibroblasts,
macrophages, mast cells, and some                                                        Elastic
white blood cells.                                                                       fibers

Function: Wraps and cushions
organs; its macrophages phagocytize
bacteria; plays important role in                                                        Collagen
inflammation; holds and conveys                                                          fibers
tissue fluid.
Location: Widely distributed under
epithelia of body, e.g., forms lamina
propria of mucous membranes;
packages organs; surrounds


                                         Photomicrograph: Areolar connective tissue, a
Lamina                                   soft packaging tissue of the body (300x).
Adipose (loose connective tissue)
Description: Matrix as in areolar,
but very sparse; closely packed
adipocytes, or fat cells, have
nucleus pushed to the side by large
fat droplet.

Function: Provides reserve food                                                     Nucleus of
fuel; insulates against heat loss;                                                  fat cell
supports and protects organs.

Location: Under skin in the
hypodermis; around kidneys and
eyeballs; within abdomen; in breasts.
                          Adipose                                                   Vacuole
                          tissue                                                    containing
                                                                                    fat droplet

                                        Photomicrograph: Adipose tissue from the
                          Mammary       subcutaneous layer under the skin (350x).
Reticular (loose connective tissue)
Description: Network of reticular
fibers in a typical loose ground
substance; reticular cells lie on the

Function: Fibers form a soft internal
skeleton (stroma) that supports other
cell types including white blood cells,
mast cells, and macrophages.
                                                                                               White blood
Location: Lymphoid organs (lymph                                                               (lymphocyte)
nodes, bone marrow, and spleen).



                                          Photomicrograph: Dark-staining network of reticular
                                          connective tissue fibers forming the internal skeleton
                                          of the spleen (350x).
 Dense Regular Connective tissue
Description: Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast.

Function: Attaches muscles to                                                        fibers
bones or to muscles; attaches bones
to bones; withstands great tensile
stress when pulling force is applied
in one direction.

Location: Tendons, most
ligaments, aponeuroses.
                                                                                     Nuclei of

                                         Photomicrograph: Dense regular connective
                                         tissue from a tendon (500x).
Dense Irregular Connective Tissue
  Description: Primarily
  irregularly arranged collagen
  fibers; some elastic fibers;
  major cell type is the fibroblast.
                                                                                  Nuclei of
  Function: Able to withstand                                                     fibroblasts
  tension exerted in many
  directions; provides structural

  Location: Fibrous capsules of
  organs and of joints; dermis of
  the skin; submucosa of
  digestive tract.                                                                Collagen

                                       Photomicrograph: Dense irregular
                                       connective tissue from the dermis of the
                                       skin (400x).
  Elastic (dense connective tissue)
Description: Dense regular
connective tissue containing a high
proportion of elastic fibers.

Function: Allows recoil of tissue
following stretching; maintains
pulsatile flow of blood through
arteries; aids passive recoil of lungs
following inspiration.
                                                                                         Elastic fibers
Location: Walls of large arteries;
within certain ligaments associated
with the vertebral column; within the
walls of the bronchial tubes.


                                         Photomicrograph: Elastic connective tissue in
Heart                                    the wall of the aorta (250x).
    Connective Tissue: Cartilage
   cartilage lacks blood vessels (avascular)
   Cartilage Cells:
    ◦ Chondroblasts – immature cartilage cells; produce
      extracellular material (matrix)
    ◦ Chondrocytes – mature cartilage cells; once trapped
      in matrix, chondroblasts become chondrocytes
 Three     types of cartilage:
    ◦ Hyaline cartilage
    ◦ Elastic cartilage
    ◦ Fibrocartilage
Hyaline Cartilage
Description: Amorphous but firm
matrix; collagen fibers form an
imperceptible network; chondroblasts
produce the matrix and when mature
(chondrocytes) lie in lacunae.

Function: Supports and reinforces;
has resilient cushioning properties;
resists compressive stress.
Location: Forms most of the
embryonic skeleton; covers the ends                                                       Chondrocyte
of long bones in joint cavities; forms                                                    in lacuna
costal cartilages of the ribs; cartilages
of the nose, trachea, and larynx.


Costal                                      Photomicrograph: Hyaline cartilage from the
cartilages                                  trachea (750x).
Elastic Cartilage
Description: Similar to hyaline
cartilage, but more elastic fibers
in matrix.

Function: Maintains the shape
of a structure while allowing                                                  Chondrocyte
great flexibility.                                                             in lacuna

Location: Supports the external                                                Matrix
ear (pinna); epiglottis.

                                     Photomicrograph: Elastic cartilage from
                                     the human ear pinna; forms the flexible
                                     skeleton of the ear (800x).
 Description: Matrix similar to
 but less firm than that in hyaline
 cartilage; thick collagen fibers

 Function: Tensile strength
 with the ability to absorb
 compressive shock.

 Location: Intervertebral discs;
 pubic symphysis; discs of knee
 joint.                                                                              Chondrocytes
                                                                                     in lacunae

                                      Photomicrograph: Fibrocartilage of an
                                      intervertebral disc (125x). Special staining
                                      produced the blue color seen.
Osseous (Bone) Tissue
 Description: Hard, calcified
 matrix containing many collagen
 fibers; osteocytes lie in lacunae.
 Very well vascularized.

 Function: Bone supports and                                                  Central
 protects (by enclosing);                                                     canal
 provides levers for the muscles                                              Lacunae
 to act on; stores calcium and
 other minerals and fat; marrow
 inside bones is the site for blood
 cell formation (hematopoiesis).
 Location: Bones

                                      Photomicrograph: Cross-sectional view
                                      of bone (125x).
Excitable Tissues: Muscular &
   excitability – ability to respond to stimuli
    ◦ a characteristic of all living cells but developed to highest
      degree in nervous and muscular tissues
   membrane potential – electrical charge difference
    (voltage) that occurs across the plasma
    membranes is the basis for their excitation
    ◦ respond quickly to outside stimulus by means of changes
      in membrane potential
    ◦ nerves – changes result in rapid transmission of signals
      to other cells
    ◦ muscles – changes result in contraction, shortening of
      the cell
Muscular Tissue Functions
   muscular tissue is made up of elongated cells
    that are specialized to contract in response
    to stimulation
   primary job is to exert physical force on
    other tissues and organs
   creates movements involved in body and
    limb movement, digestion, waste elimination,
    breathing, speech, and blood circulation
   important source of body heat
   three types of muscle: skeletal, cardiac, and
Muscle Tissue
   Skeletal muscle
    ◦ Voluntary muscle
    ◦ Striated muscle
    ◦ Multinucleated
   Cardiac muscle (myocardium)
    ◦ Involuntary muscle
    ◦ Striated; Intercalated disks
    ◦ Uninucleated
   Smooth muscle (visceral muscle)
    ◦ Involuntary muscle
    ◦ Non-striated
    ◦ uninucleated
Skeletal muscle
 Description: Long, cylindrical,
 multinucleate cells; obvious

 Function: Voluntary movement;
 locomotion; manipulation of the
 environment; facial expression;                                                      Nuclei
 voluntary control.

 Location: In skeletal muscles
 attached to bones or
 occasionally to skin.
                                                                                      Part of
                                                                                      fiber (cell)

                                   Photomicrograph: Skeletal muscle (approx. 460x).
                                   Notice the obvious banding pattern and the
                                   fact that these large cells are multinucleate.
Cardiac Muscle
 Description: Branching,
 striated, generally uninucleate
 cells that interdigitate at
 specialized junctions
 (intercalated discs).

 Function: As it contracts, it
 propels blood into the
 circulation; involuntary control.
 Location: The walls of the
 heart.                                                                               Nucleus

                                     Photomicrograph: Cardiac muscle (500X);
                                     notice the striations, branching of cells, and
                                     the intercalated discs.
Smooth muscle
 Description: Spindle-shaped
 cells with central nuclei; no
 striations; cells arranged
 closely to form sheets.

 Function: Propels substances                                                        Smooth
 or objects (foodstuffs, urine,                                                      muscle
 a baby) along internal passage-                                                     cell
 ways; involuntary control.

 Location: Mostly in the walls                                                       Nuclei
 of hollow organs.

                                   Photomicrograph: Sheet of smooth muscle (200x).
Nervous Tissue
Body’s communication system is made of
  nervous tissue
 Brain
 Nerves
 Spinal cord
The Neuron
 The main cell type of nervous tissue
 A neuron has 3 parts:
    ◦ Nerve cell body
    ◦ Dendrite
    ◦ Axon
   Neuroglia (glial cells) support and protect
    the neurons neurons and nervous tissue.
Nervous tissue
 Description: Neurons are
 branching cells; cell processes
 that may be quite long extend from
 the nucleus-containing cell body;
 also contributing to nervous tissue
 are nonirritable supporting cells                                         Nuclei of
 (not illustrated).                                                        supporting
     Neuron processes Cell body

 Axon    Dendrites
                                                                           Cell body
                                                                           of a neuron

 Function: Transmit electrical
 signals from sensory receptors
 and to effectors (muscles and
 glands) which control their activity.                                     Neuron
 Location: Brain, spinal
 cord, and nerves.

                                         Photomicrograph: Neurons (350x)
   Thin sheets of tissue that cover surfaces, line body cavities,
    line hollow organs or anchor an organ
   Epithelial Membranes
    ◦ Serous
    ◦ Mucous
    ◦ Cutaneous

   Connective Membranes
    ◦   Synovial membranes
    ◦   Meninges
    ◦   Superficial (subcutaneous) fascia
    ◦   Deep fascia
    ◦   Fibrous pericardium
    ◦   Periosteum
    ◦   Perichondrium
Serous Membranes
Three types of serous membranes
 Pleurae
 Serous pericardium
 Peritoneum

Organization of the serous membrane
 Parietal layer
 Visceral layer
Mucous Membranes
Vary in structure and function
 Trap and remove foreign particles
 Protect deeper tissue
 Absorb food materials
Benign and Malignant Tumors
 Abnormal growth of cells is called a tumor
   or neoplasm.
  Benign
  Malignant
  Cancer
Benign Tumors
Do not invade other tissues or spread to other sites
 Papilloma – in epithelium (ex. Wart)
 Adenoma – in a gland
 Lipoma – adipose tissue
 Osteoma – in bone
 Myoma – in muscle tissue. (most commonly smooth
 Angioma – in small blood vessels (ex.
 Nevus – in skin (ex. Moles)
 Chondroma – in cartilage
Malignant Tumors
Classified according to tissues of origin
 Carcinoma – form in epithelium (ex. Skin, breast,
  lungs, prostate, colon, stomach, uterus)
 Sarcoma – form in connective tissue (anywhere in
  the body)

Classified according to cells of origin
 Neuroma – originate in nerves
 Glioma – originate in neuroglia (of brain and spinal
 Lymphoma – in lymphatic tissue
 Leukemia – in white blood cells
Symptoms of Cancer
   Unusual bleeding or discharge
   Persistent indigestion
   Chronic hoarseness or cough
   Changes in the color or size of moles
   Sore that does not heal
   Unusual lump
   White patches in mouth or white spots on
   Weight loss
   Pain
Treatment of Cancer
Treatment methods may be combined
 Surgery
 Radiation
 Chemotherapy
 Immunotherapy
 Hormone receptor blockers
 Angiogenesis blockers
Tissues and Aging
Tissues lose elasticity as they age
 Skin
 Blood vessels
 Tendons and ligaments
 Bones
 Muscles
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