An Overview of Anatomy
and Physiology (pp. 23)
Topics of Anatomy (p. 2)
Topics of Physiology (pp. 23)
Complementarity of Structure
and Function (p. 3)
Levels of Structural
Organization (pp. 34)
Maintaining Life (pp. 48)
Necessary Life Functions (pp. 48)
Survival Needs (p. 8)
Homeostasis (pp. 811)
Homeostatic Control (pp. 911)
elcome to the study of one of the most fascinating subjects
Homeostatic Imbalance (p. 11)
possible--your own body. Such a study is not only highly
The Language of Anatomy (pp. 1120) personal, but timely as well. We get news of some medical
advance almost daily. To appreciate emerging discoveries in genetic
Anatomical Position and Directional
Terms (p. 13)
engineering, to understand new techniques for detecting and treating
disease, and to make use of published facts on how to stay healthy, you'll
Regional Terms (p. 14) find it helpful to learn about the workings of your body. If you are
Anatomical Variability (p. 14) preparing for a career in the health sciences, the study of anatomy and
Body Planes and Sections (p. 14)
physiology has added rewards because it provides the foundation
needed to support your clinical experiences.
Body Cavities and Membranes (pp. 1420)
2 U NI T 1 Organization of the Body
In this chapter we define and contrast anatomy and physiol- Another subdivision of gross anatomy is surface anatomy,
ogy and discuss how the human body is organized. Then we re- the study of internal structures as they relate to the overlying
view needs and functional processes common to all living skin surface. You use surface anatomy when you identify the
organisms. Three essential concepts--the complementarity of bulging muscles beneath a bodybuilder's skin, and clinicians use
structure and function, the hierarchy of structural organization, it to locate appropriate blood vessels in which to feel pulses and
and homeostasis--will unify and form the bedrock for your draw blood.
study of the human body. The final section of the chapter deals Microscopic anatomy deals with structures too small to be
with the language of anatomy--terminology that anatomists seen with the naked eye. For most such studies, exceedingly
use to describe the body or its parts. thin slices of body tissues are stained and mounted on glass
1 slides to be examined under the microscope. Subdivisions of
microscopic anatomy include cytology (si-tolo-je), which con-
An Overview of Anatomy siders the cells of the body, and histology (his-tolo-je), the
study of tissues.
and Physiology Developmental anatomy traces structural changes that oc-
Define anatomy and physiology and describe their cur in the body throughout the life span. Embryology (embre-
subdivisions. olo-je), a subdivision of developmental anatomy, concerns
Explain the principle of complementarity. developmental changes that occur before birth.
Some highly specialized branches of anatomy are used pri-
Two complementary branches of science--anatomy and marily for medical diagnosis and scientific research. For exam-
physiology--provide the concepts that help us to understand ple, pathological anatomy studies structural changes caused by
the human body. Anatomy studies the structure of body parts disease. Radiographic anatomy studies internal structures as
and their relationships to one another. Anatomy has a certain visualized by X-ray images or specialized scanning procedures.
appeal because it is concrete. Body structures can be seen, felt, Subjects of interest to anatomists range from easily seen
and examined closely. You don't need to imagine what they structures down to the smallest molecule. In molecular biol-
look like. ogy, for example, the structure of biological molecules
Physiology concerns the function of the body, in other words, (chemical substances) is investigated. Molecular biology is
how the body parts work and carry out their life-sustaining actually a separate branch of biology, but it falls under the
activities. When all is said and done, physiology is explainable anatomy umbrella when we push anatomical studies to the
only in terms of the underlying anatomy. subcellular level.
To simplify the study of the body, when we refer to body One essential tool for studying anatomy is a mastery of
structures and/or physiological values (body temperature, heart anatomical terminology. Others are observation, manipulation,
rate, and the like), we will assume that we are talking about a and, in a living person, palpation (feeling organs with your
healthy young (22-year-old) male weighing about 155 lb (the hands) and auscultation (listening to organ sounds with a
reference man) or a healthy young female weighing about 125 lb stethoscope). A simple example illustrates how some of these
(the reference woman). tools work together in an anatomical study.
Let's assume that your topic is freely movable joints of the
body. In the laboratory, you will be able to observe an animal
Topics of Anatomy joint, noting how its parts fit together. You can work the joint
Anatomy is a broad field with many subdivisions, each provid- (manipulate it) to determine its range of motion. Using
ing enough information to be a course in itself. Gross, or anatomical terminology, you can name its parts and describe
macroscopic, anatomy is the study of large body structures how they are related so that other students (and your instruc-
visible to the naked eye, such as the heart, lungs, and kidneys. tor) will have no trouble understanding you. The list of word
Indeed, the term anatomy (derived from the Greek words roots (at the back of the book) and the glossary will help you
meaning "to cut apart") relates most closely to gross anatomy with this special vocabulary.
because in such studies preserved animals or their organs are Although you will make most of your observations with the
dissected (cut up) to be examined. naked eye or with the help of a microscope, medical technology
Gross anatomy can be approached in different ways. In has developed a number of sophisticated tools that can peer
regional anatomy, all the structures (muscles, bones, blood ves- into the body without disrupting it. Read about these exciting
sels, nerves, etc.) in a particular region of the body, such as the medical imaging techniques in A Closer Look on pp. 1819.
abdomen or leg, are examined at the same time.
In systemic anatomy (sis-temik),* body structure is studied Topics of Physiology
system by system. For example, when studying the cardiovascu-
lar system, you would examine the heart and the blood vessels Like anatomy, physiology has many subdivisions. Most of
of the entire body. them consider the operation of specific organ systems. For ex-
ample, renal physiology concerns kidney function and urine
*For the pronunciation guide rules, see the Preface to the Student.
production. Neurophysiology explains the workings of the
Chapter 1 The Human Body: An Orientation 3
nervous system. Cardiovascular physiology examines the op- widely in size and shape, reflecting their unique functions in
eration of the heart and blood vessels. While anatomy provides the body.
us with a static image of the body's architecture, physiology re- The simplest living creatures are single cells, but in complex
veals the body's dynamic and animated workings. organisms such as human beings, the hierarchy continues on to
Physiology often focuses on events at the cellular or mo- the tissue level. Tissues are groups of similar cells that have a
lecular level. This is because the body's abilities depend on common function. The four basic tissue types in the human
those of its individual cells, and cells' abilities ultimately de- body are epithelium, muscle, connective tissue, and nervous
pend on the chemical reactions that go on within them. tissue.
Physiology also rests on principles of physics, which help to Each tissue type has a characteristic role in the body, which
explain electrical currents, blood pressure, and the way mus- we explore in Chapter 4. Briefly, epithelium covers the body sur- 1
cles use bones to cause body movements, among other face and lines its cavities. Muscle provides movement. Connec-
things. We present basic chemical and physical principles in tive tissue supports and protects body organs. Nervous tissue
Chapter 2 and throughout the book as needed to explain provides a means of rapid internal communication by transmit-
physiological topics. ting electrical impulses.
An organ is a discrete structure composed of at least two tis-
sue types (four is more common) that performs a specific
Complementarity of Structure and Function function for the body. The liver, the brain, and a blood vessel
Although it is possible to study anatomy and physiology indi- are very different from the stomach, but each is an organ. You
vidually, they are really inseparable because function always re- can think of each organ of the body as a specialized functional
flects structure. That is, what a structure can do depends on its center responsible for a necessary activity that no other organ
specific form. This key concept is called the principle of com- can perform.
plementarity of structure and function. At the organ level, extremely complex functions become
For example, bones can support and protect body organs be- possible. Let's take the stomach for an example. Its lining is an
cause they contain hard mineral deposits. Blood flows in one di- epithelium that produces digestive juices. The bulk of its wall is
rection through the heart because the heart has valves that muscle, which churns and mixes stomach contents (food). Its
prevent backflow. Throughout this book, we accompany a de- connective tissue reinforces the soft muscular walls. Its nerve
scription of a structure's anatomy with an explanation of its fibers increase digestive activity by stimulating the muscle to
function, and we emphasize structural characteristics con- contract more vigorously and the glands to secrete more diges-
tributing to that function. tive juices.
The next level of organization is the organ system level.
C H E C K Y O U R U N D E R S TA N D I N G Organs that work together to accomplish a common purpose
1. In what way does physiology depend on anatomy?
make up an organ system. For example, the heart and blood
2. Would you be studying anatomy or physiology if you investi-
vessels of the cardiovascular system circulate blood continu-
gated how muscles shorten? If you explored the location of
ously to carry oxygen and nutrients to all body cells. Besides
the lungs in the body?
the cardiovascular system, the other organ systems of the
body are the integumentary, skeletal, muscular, nervous, en-
For answers, see Appendix G. docrine, lymphatic, respiratory, digestive, urinary, and
reproductive systems. (Note that the immune system is
closely associated with the lymphatic system.) Look ahead to
Figure 1.3 on pp. 6 and 7 for an overview of the 11 organ sys-
Levels of Structural Organization tems, which we discuss in the next section and study in more
Name the different levels of structural organization that detail in Units 25.
make up the human body, and explain their relationships. The highest level of organization is the organism, the living
human being. The organismal level represents the sum total of
List the 11 organ systems of the body, identify their
all structural levels working together to keep us alive.
components, and briefly explain the major function(s) of
C H E C K Y O U R U N D E R S TA N D I N G
The human body has many levels of structural organization 3. What level of structural organization is typical of a cytolo-
(Figure 1.1). The simplest level of the structural hierarchy is gist's field of study?
the chemical level, which we study in Chapter 2. At this level, 4. What is the correct structural order for the following terms:
atoms, tiny building blocks of matter, combine to form tissue, organism, organ, cell?
molecules such as water and proteins. Molecules, in turn, asso- 5. Which organ system includes the bones and cartilages?
ciate in specific ways to form organelles, basic components of Which includes the nasal cavity, lungs, and trachea?
the microscopic cells. Cells are the smallest units of living For answers, see Appendix G.
things. We examine the cellular level in Chapter 3. All cells
have some common functions, but individual cells vary
4 U NI T 1 Organization of the Body
Smooth muscle cell
1 Chemical level 2 Cellular level
Atoms combine to form molecules. Cells are made up of molecules.
Smooth muscle tissue
Cardiovascular 3 Tissue level
Tissues consist of similar types of cells.
vessels Blood vessel (organ)
Smooth muscle tissue
4 Organ level
Organs are made up of different types of tissues.
6 Organismal level 5 Organ system level
The human organism is made up of many Organ systems consist of different
organ systems. organs that work together closely.
Figure 1.1 Levels of structural organization. Components of the cardiovascular system are
used to illustrate the levels of structural organization in a human being.
Maintaining Life Like all complex animals, humans maintain their bound-
aries, move, respond to environmental changes, take in and
List the functional characteristics necessary to maintain life digest nutrients, carry out metabolism, dispose of wastes, repro-
in humans. duce themselves, and grow. We will introduce these necessary
List the survival needs of the body. life functions here and discuss them in more detail in later
We cannot emphasize too strongly that all body cells are in-
Necessary Life Functions terdependent. This interdependence is due to the fact that
Now that you know the structural levels of the human body, the humans are multicellular organisms and our vital body func-
question that naturally follows is: What does this highly orga- tions are parceled out among different organ systems. Organ
nized human body do?
Chapter 1 The Human Body: An Orientation 5
systems, in turn, work cooperatively to promote the well-being Digestive system Respiratory system
Takes in nutrients, breaks them Takes in oxygen and
of the entire body. This theme is repeated throughout the book. down, and eliminates unabsorbed eliminates carbon dioxide
Figure 1.2 identifies some of the organ systems making major matter (feces)
contributions to necessary life functions. Also, as you read this Food O2 CO2
section, check Figure 1.3 for more detailed descriptions of the
body's organ systems.
Via the blood, distributes oxygen
Maintaining Boundaries and nutrients to all body cells and
delivers wastes and carbon
Every living organism must maintain its boundaries so that its dioxide to disposal organs
internal environment (its inside) remains distinct from the ex- 1
ternal environment surrounding it (its outside). In single-celled Blood
organisms, the external boundary is a limiting membrane that CO2
encloses its contents and lets in needed substances while re- O2
stricting entry of potentially damaging or unnecessary sub-
stances. Similarly, all the cells of our body are surrounded by a
selectively permeable membrane. Heart
Additionally, the body as a whole is enclosed and protected Nutrients Eliminates
by the integumentary system, or skin (Figure 1.3a). This system nitrogenous
protects our internal organs from drying out (a fatal change), wastes and
Interstitial fluid excess ions
bacteria, and the damaging effects of heat, sunlight, and an un-
believable number of chemicals in the external environment.
Movement includes the activities promoted by the muscular
system, such as propelling ourselves from one place to another
by running or swimming, and manipulating the external envi- Nutrients and wastes pass
ronment with our nimble fingers (Figure 1.3c). The skeletal sys- between blood and cells
tem provides the bony framework that the muscles pull on as via the interstitial fluid
they work (Figure 1.3b). Movement also occurs when sub-
stances such as blood, foodstuffs, and urine are propelled Integumentary system
through internal organs of the cardiovascular, digestive, and Feces Protects the body as a whole Urine
urinary systems, respectively. On the cellular level, the muscle from the external environment
cell's ability to move by shortening is more precisely called
contractility. Figure 1.2 Examples of interrelationships among body organ
Responsiveness, or irritability, is the ability to sense changes
(which serve as stimuli) in the environment and then respond amoeba, the cell itself is the "digestion factory," but in the multi-
to them. For example, if you cut your hand on broken glass, a cellular human body, the digestive system performs this func-
withdrawal reflex occurs--you involuntarily pull your hand tion for the entire body (Figure 1.3i).
away from the painful stimulus (the broken glass). You don't
have to think about it--it just happens! Likewise, when carbon Metabolism
dioxide in your blood rises to dangerously high levels, chemical Metabolism (me -tabo-lizm; "a state of change") is a broad
sensors respond by sending messages to brain centers control- term that includes all chemical reactions that occur within body
ling respiration, and you breathe more rapidly. cells. It includes breaking down substances into their simpler
Because nerve cells are highly irritable and communicate building blocks (more specifically, the process of catabolism),
rapidly with each other via electrical impulses, the nervous synthesizing more complex cellular structures from simpler
system is most involved with responsiveness (Figure 1.3d). substances (anabolism), and using nutrients and oxygen to pro-
However, all body cells are irritable to some extent. duce (via cellular respiration) ATP, the energy-rich molecules
that power cellular activities. Metabolism depends on the diges-
Digestion tive and respiratory systems to make nutrients and oxygen avail-
Digestion is the breaking down of ingested foodstuffs to simple able to the blood and on the cardiovascular system to distribute
molecules that can be absorbed into the blood. The nutrient- them throughout the body (Figure 1.3i, h, and f, respectively).
rich blood is then distributed to all body cells by the cardiovas- Metabolism is regulated largely by hormones secreted by en-
cular system. In a simple, one-celled organism such as an docrine system glands (Figure 1.3e).
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