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					           Chapter 1: An introduction to the Structure and Function of the Body
                                                     Group: Pathology

Introduction
There are many wonders in our world, but none is more amazing than the human body. This is a textbook about this
incomparable structure. It deals with two very distinct and yet interrelated sciences: anatomy and physiology

As a science, anatomy is defined as the study of the structure of an organism and the relationship of its parts. The
term anatomy is derived from two Greek words that mean “a cutting up.” Anatomists learn about the structure of
the human body by cutting it apart. This process, called dissection, is still the main technique used to study the
structures of the human body.

Physiology, on the other hand, is the study of the functions (jobs) of living organisms and their parts. It is a changing
science that requires active experimentation. In the chapters that follow, you will see again and again that anatomical
structures are exactly made to perform specific functions. Each has a particular size, shape, form, or position in the
body related directly to its ability to perform a special function.

Although an understanding of the normal structure and function of the body is important, it is also important to
know the mechanisms (methods) of disease. Disease conditions happen because of abnormalities (things that are not
normal) of body structure or function that stop the body from keeping the internal stability that keeps us alive and
healthy. Pathology, the study of disease, uses principals (ideas) from anatomy and physiology to find out the nature
of diseases. The term pathology comes from pathos, the Greek word for “disease.’ Chapter 5 provides an overview of
the basic mechanisms of disease, such as infection and cancer. Throughout the rest of this textbook, explanations of
normal structure and function are presented along with discussions of related disease processes. By knowing the
structure and function of a healthy body, you will be better able to understand what can go wrong to cause disease.
At the same time, knowledge of disease states will increase your understanding of normal structure and function.

SUMMARY:

          Anatomy is the study of the body’s structure and the relationship of its parts
          Physiology is the study of how the body works
          Pathology is the study of disease and uses ideas from Anatomy and Physiology to work

Section 1.1: Structural Levels of Organization
Before you begin the study of structure and function of the human body and its many parts, it is important to think
about how those parts are organized and how they might logically fit together into a functioning whole. Examine
Figure 1-1. It illustrates the different levels or organization that influences body structure and function. Note that the
levels of organization move from the least complex (chemical level) to the most complex (organism level).

Organization is one of the most important characteristics of body structure. Even the word organism, or a living
thing, implies organization.

        Summary: All living things are organized into different levels

Although the body itself is considered a single structure, it is made up of trillions of smaller structures. Atoms and
molecules are often referred to as the chemical level of organization. The existence of life depends on the proper
levels of proportions of many chemical substances in the cells of the body.
Many of the physical and chemical phenomena that play important roles in the life process are reviewed in Chapter
2. Such information gives an understanding of the base for life and for the study of the next levels of organization
that are so important in the study of anatomy and physiology- cells, tissues, organs, and systems.

    Summary: the Chemical level of organization is the smallest level of organization and life depends on these tiny
     things.

Cells are considered to be the smallest “living” units of structure and function in our bodies. Although long
recognized as the simplest units of living matter, cells are far from simple. They are extremely complex, a fact you will
                                                                                                review in Chapter 3.



                                                                                               Tissues are more
                                                                                               complex than cells. By
                                                                                               definition a tissue is an
                                                                                               organization of many
                                                                                               cells that act together to
                                                                                               perform (do) a common
                                                                                               function. The cells of a
                                                                                               tissue may be of several
                                                                                               types but all are working
                                                                                               together in some way to
                                                                                               make the structural and
                                                                                               functional qualities of
                                                                                               the tissue. Cells of a
                                                                                               tissue are often held
                                                                                               together and surrounded
                                                                                               by varying amounts and
                                                                                               varieties of glue-like,
                                                                                               nonliving intercellular
                                                                                               substances.

                                                                                            Organs are larger and
                                                                                            even more complex than
                                                                                            tissues. An organ is a
                                                                                            group of several
                                                                                            different kinds of tissues
                                                                                            arranged so that they
                                                                                            can act together as a unit
                                                                                            to perform a special
                                                                                            function. For instance,
                                                                                            the heart shown in
                                                                                            Figure 1-1 is an example
                                                                                            of organization at the
                                                                                            organ level. Unlike
microscopic molecules and cells, some tissues and most organs are gross (large) structures that can be seen easily
without a microscope.
Systems are the most complex units that make up the body. A system is an organization of varying numbers and
kinds of organs arranged so that they can together perform complex functions for the body. The organs of the
cardiovascular system shown in Figure 1-1 allow blood to carry nutrients, oxygen, and wastes to and from the tissues
of the body. The heart and each of the blood vessels are the organs that pump blood and carry it throughout the
body as it performs its functions.

The body as a whole-the human organism- is all the atoms, molecules, cells, tissues, organs, and systems that you will
study in subsequent chapters of this text. Although capable of being dissected or broken down into many parts, the
body is a unified and complex collection of structurally and functionally interactive parts, each working together to
ensure healthy survival.

SUMMARY

     Cells are made up of the chemical level- atoms, molecules, particles
     Tissues are made up of cells- sometimes more than one type of cell
     Organs are made up of tissues, sometimes more than one type of tissue
     Systems are made up of organs, sometimes more than one type of organ
     All the systems make up an organism.

Section 1.2: Anatomical Position
Discussions about the body, the way it moves, its posture, or the relationship of one
area to another assume that the body as a whole is in a specific position called the
anatomical position. In this reference positions (Figure 1-2) the body is in an erect or
standing posture with the arms at the sides and palms turned forward. The head also
points forward, as do the feet, which are aligned at the toe and set slightly apart. The
anatomical position is a reference position that gives meaning to the directional terms
used to describe the body parts and regions. In other words, you need to know the
anatomical position so that you know how to apply the directional terms correctly no
matter what position the body being described is in.
                                                                                                     Figure 1-2
Supine and Prone are terms used to describe the position of the body when it is not in the anatomical position. In the
supine position the body is laying face upward, and in the prone position the body is laying face downward.

SUMMARY

     Anatomists and Physiologists use the anatomical position to describe were something is located in the body
     The anatomical position is standing straight up, head and feet forward, arms at the side with palms facing
      forward.

Section 1.3: Anatomical Directions
When studying the body, it is often helpful to know where an organ is in relation to other structures. The following
directional terms are used in describing relative (in comparison to another) positions of body parts. To help you
understand them better, they are listed here in sets of opposite pairs.

     1. Superior and Inferior (Figure 1-3)- superior means “toward the head” and inferior means “toward the feet”.
        Superior also means “upper” or “above”, and inferior means “lower” or “below.” For example, the lungs are
        located superior to the diaphragm (refer to figure 1-7 if you are not sure where these are located).
     2. Anterior and Posterior (Figure 1-3)- anterior means “front” or “in front of;” Posterior means “back” or “in
        back of.” In humans, who walk in an upright position, ventral (toward the belly) can be used in place of
        anterior and dorsal (towards the back) can be used for posterior. For example, the nose is on the anterior
        surface of the body, and the shoulder blades are on its posterior surface.
     3. Medial and Lateral (Figure 1-3)- medial means “toward the midline of the body”; lateral means “toward the
        side of the body or away from the midline.” For example, the great toe is at the medial side of the foot, and
        the little toe is at its lateral side. The heart lies medial to the lungs, and the lungs lie lateral to the heart.
                                                                                             Figure 1-3
     4. Proximal and Distal (Figure 1-3)- proximal means
        “toward or nearest the trunk of the body, or nearest
        the point of origin of one of its parts”; distal means
        “away from, or farthest from the trunk or the point
        of origin of a body part.” For example, the elbow lies
        at the proximal end of the lower arm, whereas the
        hand lies at its distal end.
     5. Superficial and Deep- superficial means nearer the
        surface; deep means farther away from the body
        surface. For example, the skin of the arm is
        superficial to the muscles below it, and the bone of
        the upper arm is deep to the muscles that surround
        or cover it.

To make the reading of anatomical figures a little easier for
you, we have used an anatomical compass rosette
throughout this book. On many figures, you will see a small
compass rosette like you might see on a geographical map.
Instead of being labeled N,S,E, and W, the anatomical rosette
is labeled with abbreviated anatomical directions. For
example, in Figure 1-2, the rosette is labeled S (superior) on
top and I (inferior) on the bottom. Notice that in Figure 1-2 the rosette shows R (right) on the subject’s right- not your
right. Here are the directional abbreviations used with the rosettes in this book:

Abbreviation      Direction
A                 Anterior
D                 Distal
I                 Inferior
L (opposite R)    Left
L (opposite M)    Lateral
M                 Medial
P (opposite A)    Posterior
P (opposite D)    Proximal
R                 Right
S                 Superior
SUMMARY

     All directional terms are used in pairs. One and its opposite.
     Superior means upward, inferior means downward
     Proximal means close and Distal means further away
     Anterior means to the front, Posterior means to the back
     Lateral means to the side, Medial means to the middle
     Superficial means toward the surface (top) and Deep means away from the surface

Section 1.4: Planes or Sections of the Body
To facilitate the study of individual organs or the body as a whole, it is often useful to first subdivided or “cut” it into
smaller segments. To aid in doing this uniformly, body planes or sections have been identified with special names.
Read the following definitions and identify each of these terms in Figure 1-3.

     1. Sagittal- a sagittal cut or section is a lengthwise plane running from front to back. It divides the body or any
        of its parts into right and left sides. The sagittal plane shown in Figure 1-3 divides the body into two equal
        halves. This unique type of sagittal plane is called a midsaggital plane.
     2. Frontal- a frontal (coronal) plane is a lengthwise plane running from side to side. As you can see in Figure 1-3,
        a frontal plane divides the body or any of its parts into anterior and posterior (front and back) portions.
     3. Transverse- a transverse plane is a horizontal or crosswise plane. Such a plane (see Figure 1-3) divides the
        body or any of its parts into upper and lower portions.

SUMMARY

     In order to study the human body it is sometimes subdivided (cut) into in different ways
     Sagittal splits the body into right and left sides
     Frontal splits the body into front and back sides
     Transverse splits the body into top and bottom parts

Now: Before you continue on to the next part of the reading and study guide, you will need to take the
quiz.

Below is a link to Quia so that you can practice with the flashcards:

Chapter 1: Section 1.1-1.4 Flashcards


When you are finished studying the link below will take you to the quiz. You must pass it with a 70% or
above in order to continue on. You have three chances.

Chapter 1: Section 1.1-1.4 Quiz


Section 1.5: Body Cavities

In contrast to its outside appearance, the body is not a solid
structure. It is made up of open spaces or cavities that hold
compact, well-ordered arrangements of internal organs. The two
major body cavities are called the ventral and dorsal body
cavities. The location and outlines of the body cavities are
illustrated in Figure 1-4. The upper part of the ventral cavity
includes the thoracic cavity, a space that you may think of as your
chest cavity. Its middle area is a subdivision of the thoracic cavity
called the mediastinum; its other subdivisions are called the right
and left pleural cavities. The lower part of the ventral cavity in
Figure 1-4 includes an abdominal cavity and pelvic cavity.
Actually, these two form only one cavity, the abdominopelvic
cavity, because no physical barrier separates them. In Figure 1-4 a
dotted line shows the approximate point of separation between the abdominal and pelvic subdivisions. Notice,
however, that an actual physical barrier separates the thoracic cavity from the abdominal cavity. This muscular sheet
is the diaphragm. It is dome-shaped and is the most important muscle for breathing.

                                          To make it easier to locate organs in the large abdominopelvic cavity,
          Figure 1-5                      anatomists have divided the abdominopelvic cavity into four quadrants:
                                          right and upper or superior, right lower or interior, left upper or superior,
                                          and left lower or inferior. As you can see in Figure 1-5, the midsagittal and
                                          transverse planes, which were described in the previous section, pass
                                          through the navel (umbilicus) and divide the abdominopelvic region into the
                                          four quadrants. This method of subdividing the abdominopelvic cavity is
                                          frequently used by healthy professionals and is useful for locating the
                                          location of pain or describing the location of a tumor or other abnormality.

                                          Another and perhaps more precise way to divide the abdominopelvic cavity
                                          is shown in Figure 1-6. Here, the abdominopelvic cavity is subdivided into
                                          nine regions defined as follows:

                                               1. Upper abdominopelvic                       Figure 1-6
                                           regions- the right and left
                                           hypochondriac regions and the
                                           epigastric region lie above an
                                           imaginary line across the
       abdomen at the level of the ninth rib cartilages.
    2. Middle regions- the right and left lumbar regions and the
       umbilical region lie below an imaginary line across the abdomen
       at the level of the ninth rib cartilages and above the imaginary
       lines across the abdomen at the top of the hip bones.
    3. Lower regions- the right and left iliac (or inguinal) regions and the
       hypogastric region lie below an imaginary line across the
       abdomen at the level of the top of the hip bones.

The dorsal cavity shown in Figure 1-4 includes the space inside the skull
that holds the brain; it is called the cranial cavity. The space inside the
spinal column is called the spinal cavity; it contains the spinal cord. The
cranial and spinal cavities are dorsal cavities, whereas the thoracic and
abdominopelvic cavities are ventral cavities.

Knowledge of the body cavities has important medical uses. For example, one can locate specific organs by knowing
in which cavity they are found. Some of the organs in the larges body cavities are visible in Figure 1-7 and are listed in
Table 1-1.

Table 1-1 Body Cavities
VENTRAL BODY CAVITY
Thoracic Cavity
   Mediastinum                Heart, trachea, esophagus, thymus, blood vessels
   Pleural Cavities           Lungs
Abdominopelvic cavity
   Abdominal Cavity           Liver, gallbladder, stomach, spleen, pancreas, small intestine, parts of large intestine
    Pelvic Cavity             Lower (sigmoid) colon, rectum, urinary bladder, reproductive organs
DORSAL BODY CAVITY
Cranial Cavity                Brain
Spinal Cavity                 Spinal Cord
SUMMARY

    The body is not a solid structure it has cavities (spaces) within it. The two major categories are Ventral and
     Dorsal
    Each cavity can be divided into more specific areas. For example: The thoracic cavity can be divided into the
     mediastinum and the pleural cavities.



                                                                                        Figure 1-7




Section 1.6: Body Regions
To recognize something, you usually first notice its overall structure and form (shape). For example, a car is
recognized as a car before the specific details of its tires, grill, or wheel covers are noticed. Recognition of the human
form also occurs as you first identify overall shape and basic outline. However, for more specific identification to
occur, details of size, shape, and appearance of individual body areas must be described. Individuals differ in overall
appearance because specific body areas such as the face or torso have unique identifying characteristics. Detailed
descriptions of the human form require that specific regions be identified and appropriate terms be used to describe
them.
The ability to identify and correctly describe specific body areas is particularly important in the health sciences. For a
patient to complain of pain in the head is not as specific, and therefore, not as useful to health professional as a more
specific description would be. Saying that the pain is facial provides additional information and helps to more
specifically identify the area of pain. By using correct anatomical terms such as forehead, cheek or chin to describe
the area of pain, attention can be focused even more quickly on the specific anatomical area that may need
attention. Familiarize yourself with the more common terms used to describe specific body regions in Figure 1-8.

The body as a whole can be divided into two major parts: axial and appendicular. The axial part of the body is made
up of the head, neck and torso or trunk; the appendicular part is made up of the upper and lower extremities. Each
major area is subdivided as shown in Figure 1-8. Note, for example, that the torso is composed of thoracic, abdominal
and pelvic areas, and the upper extremity is divided into arms, forearm, wrist and hand components (parts). Although
most terms used to describe gross body regions are well understood, misuse is common. The word leg is a good
                                                                                           example: it refers to the
                                                                                           area of the lower
                                                                                           extremity between the
                                                                                           knee and angle and not to
                                                                                           the entire lower
                                                                                           extremity.

                                                                                               The structure of the body
                                                                                               changes in many ways
                                                                                               and at varying (changing)
                                                                                               rates during a lifetime.
                                                                                               Before young adulthood,
                                                                                               the body develops and
                                                                                               grows; after young
                                                                                               adulthood, it gradually
                                          Figure 1-8                                           undergoes degenerative
                                                                                               (damaging) changes. With
                                                                                               the lowered activity of
                                                                                               the body as one advances
                                                                                               through older adulthood,
                                                                                               a generalized decrease in
                                                                                               size or wasting away of
                                                                                               many body organs and
tissues occurs that affects the structure and function of many body areas. This degenerative process, which results
from disuse( less use), is called atrophy. In many cases, atrophy can be reversed with therapy. Some tissues simply
lose their ability to regenerate as we get older. Nearly every chapter of this book refers to a few of those changes.

SUMMARY:

    The body can be divided into two parts: The axial part made up of the head, neck and the trunk; and the
     appendicular which is made up of the rest of the body

Section 1.7: The Balance of Body Functions
Although they may have very different structures, all living organisms use mechanisms that guarantee survival of the
body and success in reproducing its genes to its offspring.
Survival depends on the body keeping relatively constant (same) conditions within the body. Homeostasis is what
physiologists call the relative constancy of the internal environment. The cells of the body live in an internal
environment made up mostly of water combined with salts and other dissolved substances. Like fish in a fishbowl,
the cells are able to survive only if the conditions of their watery environment remain relatively stable-that is, only if
conditions stay within the same narrow range. The temperature, salt content, acid level (pH), fluid volume and
pressure, oxygen concentration, and other vital conditions must remain within normal limits. To keep a narrow range
of watery conditions in a fishbowl, one may add a heater, an air pump, and filters. Likewise, the body has
mechanisms (things) that act as heater, air pumps, and the like to maintain (keep) the relatively stable conditions of
its internal fluid environment.

Because the activities of cells and external disturbances (things that change the environment) area always changing
the conditions inside the body, changes occur frequently. Therefore the body must constantly work to keep or return
stability, or homeostasis. For example, the heat made by muscle activity during exercise may cause the body’s
temperature to rise above normal. The body must then release sweat, which evaporates and cools the body back to
a normal temperature. To accomplish such self-regulation, a highly complex and integrated (work together)
communication control system is required. The basic type of control system in the body is called a feedback loop.

The idea of a feedback loop is borrowed from engineering. Figure 1-9A shows how an engineer would describe the
                                                                                                 feedback loop that
                                                                                                 keeps stability of
                                                                                                 temperature in a
                                                                                                 building. Cold winds
                                                                                                 outside a building
                                                                                                 may cause a
                                                                                                 decrease in the
                                                                                                 building temperature
                                                                                                 below normal. A
                                                                                                 sensor, in this case a
                                                                                                 thermometer, senses
                                                                                                 the change in
                                                                                                 temperature.
                                                                                                 Information from the
                                                                                                 sensor feeds back (is
                                                                                                 given) to a control
                                                                                                 center- a thermostat
                                                                                                 for example- that
                                                                                                 compares the actual
                                                                                                 temperature to the
                                                                                                 normal temperature
                                                                                                 and responds by
                                                                                                 activating the
                                                                                Figure 1-9       building’s furnace.
The furnace is called the effector because it has an effect on the controlled condition (temperature). Because the
sensor continually feeds information back to the control center, the furnace will be automatically shut off when the
temperature has returned to normal.

As you can see in Figure 1-9B the body uses a similar feedback loop in restoring body temperature when we become
chilled (cold). Nerve endings that act as temperature sensors give information to a control center in the brain that
compares actual body temperature to normal body temperature. In response to a chill, the brain sends nerve signals
to muscles that shiver. Shivering makes heat that increases out body temperature. We stop shivering when feedback
information tells the brain that body temperature has increased to normal.

Feedback loops such as those shown in Figure 1-9 are called negative feedback loops because they oppose, or resist,
a change in a controlled condition. Most homeostatic control loops in the body use negative feedback because
changing back toward a normal value tends to stabilize conditions- exactly what homeostasis is all about. An example
of negative feedback loop happens when decreasing blood oxygen concentration caused by muscles using oxygen
during exercise is changed by an increase in breathing to bring the blood oxygen level back up to normal. Another
example is the excretion (getting rid ) of larger than usual amounts of urine when the amount of fluid in the body is
higher than the normal, ideal amount.

Although not common, positive feedback loops do happen in the body and are also used in normal function. Positive
feedback control loops are a stimulatory (they make something happen). Instead of opposing(resisting) a change in
the internal environment and causing a “return to normal,” positive feedback loops temporarily amplify(make bigger)
or reinforce the change that is happening. This type of feedback loop causes an always increasing rate of events to
occur until something stops the process. An example of a positive feedback loop includes the events that cause rapid
increase in uterine contractions before the birth of a baby. Another example is the increasingly rapid (fast) sticking
together of blood cells called platelets to form a plug that begins formation of a blood clot.

In each of these cases, the process increases quickly until the positive feedback loop is stopped suddenly by the birth
of a baby or the formation of a clot. In the long run, such normal positive feedback events also help maintain (keep)
constancy( same) of the internal environment.

It is important to understand that homeostatic control mechanisms can keep only a relative constancy (compared to
normal). All homeostatically controlled conditions in the body do not remain absolutely constant (same). Rather,
conditions normally fluctuate near a normal, ideal value. Thus body temperature, for example, rarely remains exactly
the same for very long it usually fluctuates up and down near a person’s normal body temperature.

Because all organs function to help maintain homeostatic balance, we will be discussing negative and positive
feedback mechanisms many times throughout the rest of the chapters of this book.

Before leaving this brief introduction to physiology, we must stop to state an important principle: the ability to
maintain (keep) the balance of body functions is related to age. During childbirth, homeostatic functions gradually
become more and more efficient and effective. They operate with the highest efficiency and effectiveness during
young adulthood. During late adulthood and old age, they gradually become less and less efficient and effective.
Changes and functions happening during the early years are called developmental processes; those occurring after
young adulthood area called aging processes. In general, development processes improve efficiency of functions;
aging, processes usually lessen it.

SUMMARY

    The body has to be able to communicate in order to keep an organism alive.
    Conditions must stay stable (same) so that an organism can survive
    The body has two different ways that it keeps the relative stability of the organism: Negative feedback loops
     and Positive Feedback Loops
    The Negative feedback loop senses a change and works to return conditions to normal
    The positive feedback loop amplifies a signal (makes it strong and its effects stronger) until something suddenly
     stops it.
Now: Before you continue on to the next part of the reading and study guide, you will need to take the
quiz.

Below is a link to Quia so that you can practice with the flashcards:

Chapter 1: Section 1.5-1.7 Flashcards


When you are finished studying the link below will take you to the quiz. You must pass it with a 70% or
above in order to continue on. You have three chances.

Chapter 1: Section 1.5-1.7 Quiz

				
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