Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Whatlies ahead is an astounding ad-
venture—learning aboutthe structure
and function of the human body and
how theyare regulated by intricate sys-
tems ofchecks and balances. For exam-
ple, tiny collectionsof cells embedded in
the pancreas affect the uptake and use of
blood sugar in the body. Eating a candybar re-
sults in an increase in blood sugar, which actsas a
stimulus. The tiny collections of cells respond to the stimulus bysecreting in-
sulin. Insulin movesinto blood vessels and is transported to cells, where it in-
creasesthe movement of sugar from the blood into cells, thereby providing the
cellswith a source of energy and causing blood sugar levels to decrease.
Knowledge ofthe structure and function of the human body provides the
basisfor understanding disease. In one type of diabetes mellitus, cellsof the pan-
creasdo not secrete adequate amounts of insulin. Not enough sugar moves into
cells, which deprivesthem of a needed source of energy, and theymalfunction.
Knowledge ofthe structure and function of the human bodyis essential for
those planning a career in the health sciences. Itis also beneficial to nonprofes-
sionals because ithelps with understanding overall health and disease, with
evaluating recommended treatments, and with criticallyreviewing advertise-
mentsand articles.
This chapter definesanatomy and physiology (2). It also explains the
body’sstructural and functional organization (5) and provides an overview ofthe
human organism(5) and homeostasis (10). Finallythe chapter presents termi-
nologyand the body plan (13).
The Human
Organism
Colorized scanning electron micrograph
(SEM) of the peritoneum covering the liver.
These flattened cellshave many short, hairlike
microvilli, and theysecrete a lubricating fluid
thatprotects the liverfrom friction as it moves
within the abdominal cavity.
CHAPTER
1
Part 1 Organization ofthe Human Body
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Anatomy and Physiology
Objective
■ Define the termsanatomy and physiology, and identify the
differentways in which they can be studied.
Anatomy is the scientific discipline that investigates the body’s
structure.For example, anatomy describes the shape and size of
bones. In addition,anatomy examines the relationship between
the structure ofa body part and its function. Just as the structure
of a hammer makes it well suited for pounding nails,the st ruc-
ture ofa specific body part allows it to perform a particular func-
tion effectively.For example, bones can provide strength and
support because bone cells surround themselves with a hard,
mineralized substance. Understanding the relationship between
structure and function makes it easier to understand and
appreciate anatomy.
Anatomy can be considered at many different levels.Devel-
opmental anatomy is the study of the structural changes that
occur between conception and adulthood.Embryology (em-bre¯-
ol⬘o¯-je¯), a subspeciality of developmental anatomy,considers
changes from conception to the end ofthe eighth week of develop-
ment.Most birth defects occur during embryologic development.
Some structures,such as cells, are so small that they are best
studied using a microscope. Cytology (sı¯-tol⬘o¯-je¯) examines the
structural features of cells, and histology (his-tol⬘o¯-je¯) examines
tissues,which are cells and the materials surrounding them.
Gross anatomy,the study of structures that can be examined
without the aid of a microscope,can be approached from either a
systemic or regional perspective.In systemic anatomy the body is
studied system by system,which is the approach taken in this and
most other introductory textbooks.A system is a group of struc-
tures that have one or more common functions.Examples are the
circulatory,nervous, respiratory,skeletal, and muscular systems. In
regional anatomythe body is studied area by area, which is the ap-
proach taken in most graduate programs at medical and dental
schools.Within each region,such as the head, abdomen, or arm, all
systems are studied simultaneously.
Surface anatomyis the study of the external form of the
body and its relation to deeper structures.For example, the ster-
num (breastbone) and parts ofthe ribs can be seen and palpated
(felt) on the front of the chest. These structures can be used as
landmarks to identify regions of the heart and points on the
chest where certain heart sounds can best be heard. Anatomic
imaging uses radiographs (x-rays), ultrasound, magnetic reso-
nance imaging (MRI),and other technologies to create pictures
of internal structures. Both surface anatomy and anatomic im-
aging provide important information about the body for
diagnosing disease.
Part1 Organization ofthe Human Body2
AnatomicAnomalies
No two humansare structurally identical. For instance, one person may
have longer fingersthan another person. Despite this variability, most
humanshave the same basic pattern. Normally, we each have 10 fingers.
Anatomicanomalies are structures that are unusual and different from
the normalpattern. For example, some individuals have 12 fingers.
Anatomicanomalies can vary in severity from the relatively
harmlessto the life-threatening, which compromise normal function. For
example, each kidneyis normally supplied byone blood vessel, but in
some individualsa kidney can be supplied by two blood vessels. Either
way, the kidneyreceives adequate blood. On the other hand, in the
condition called “blue baby” syndrome certain blood vesselsarising
from the heartof an infant are not attached in their correct locations;
blood isnot effectively pumped to the lungs, resulting in tissues not
receiving adequate oxygen.
Physiologyis the scientific investigation of the processes or
functions ofliving things. Although it may not be obvious at times,
living things are dynamic and ever-changing,not static and with-
out motion.The major goals of physiology are to understand and
predict the responses ofthe body to stimuli and to understand how
the body maintains conditions within a narrow range ofvalues in a
constantly changing environment.
Like anatomy,physiology can be considered at many differ-
ent levels. Cell physiology examines the processes occurring in
cells and systemic physiology considers the functions of organ
systems.Neurophysiology focuses on the nervous system and car-
diovascular physiology deals with the heart and blood vessels.
Physiology often examines systems rather than regions because
portions of a system in more than one region can be involved in a
given function.
The study of the human body must encompass both
anatomy and physiology because structures, functions, and
processes are interwoven.Pathology (pa-thol⬘o¯-je¯) is the medical
science dealing with all aspects ofdisease, with an emphasis on the
cause and development of abnormal conditions as well as the
structural and functional changes resulting from disease.Exercise
physiology focuses on changes in function, but also structure,
caused by exercise.
1. Define anatomy and physiology. Describe different levels at
which each can be considered.
2. Define pathology and exercise physiology.
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
3
Clinical Focus AnatomicImaging
Anatomicimaging has revolutionized medical
science. Some estimate thatduring the past
20 yearsas much progresshas been made in
clinicalmedicine as in all its previous history
combined, and anatomicimaging hasmade a
major contribution to thatprogress. Anatomic
imaging allows medical personnelto look
inside the bodywith amazing accuracy and
without the trauma and riskof exploratory
surgery. Although mostof the technology of
anatomicimaging is very new, the concept
and earliesttechnology are quite old.
Wilhelm Roentgen (1845–1923) was
the firstto use x-rays in medicine in 1895 to
see inside the body. The rayswere called
x-raysbecause no one knew whatthey were.
This extremely shortwave electromagnetic
radiation (see chapter 2) movesthrough the
bodyexposing a photographic plate to form
a radiograph (ra¯⬘de¯-o¯-graf). Bones and ra-
diopaque dyes absorb the rays and create
underexposed areas that appear white on
the photographicfilm (figure A). X-rays have
been in common use for many years and
have numerousapplications. Almost every-
one hashad a radiograph taken, either to vi-
sualize a broken bone or to checkfor a cavity
in a tooth. A major limitation ofradiographs,
however, is thatthey give only a flat, two-
dimensional(2-D) image of the body, which
isa three-dimensional (3-D) structure.
Ultrasoundis the second oldest imag-
ing technique. Itwas first developed in the
early1950s as an extension of World War II
sonar technology and uses high-frequency
sound waves. The sound wavesare emitted
from a transmitter–receiver placed on the
skin over the area to be scanned. The sound
waves strike internal organs and bounce
back to the receiver on the skin. Even
though the basictechnology is fairly old, the
most important advances in the field oc-
curred onlyafter it became possible to ana-
lyze the reflected sound wavesby computer.
Once the computer analyzesthe pattern of
sound waves, the information istransferred
to a monitor, where the resultis visualized
asan ultrasound image called a sonogram
(son⬘o¯-gram) (figure B). One of the more re-
cent advancesin ultrasound technology is
the ability of more advanced computersto
analyze changesin position through time
and to displaythose changes as “real time”
movements. Among other medicaluses, ul-
trasound iscommonly used to evaluate the
condition ofthe fetus during pregnancy.
Computer analysisis also the basis of
another major medicalbreakthrough in im-
aging. Computed tomographic (to¯⬘mo¯-
graf⬘ik) (CT) scans, developed in 1972 and
originally called computerized axial tomo-
graphic(CAT) scans, are computer-analyzed
x-rayimages. A low-intensity x-raytube is ro-
tated through a 360-degree arc around the
patient, and the imagesare fed into a com-
puter. The computer then constructsthe im-
age ofa “slice” through the body at the point
where the x-raybeam was focused and ro-
tated (figure C). Itis also possible with some
computers to take severalscans short dis-
tancesapart and stack the slices to produce
a 3-D image ofa part of the body (figure D).
Figure D
Computed Tomography
(CT)
Stacking ofimagesacquired using CT technology.
Figure A
X-ray
Radiograph produced byx-raysshows a lateral
view ofthe head and neck.
Figure B
Ultrasound
Sonogram produced with ultrasound showsa
lateralview of the head and hand of a fetus
within the uterus.
Figure C
Computed Tomography
Transverse section through the skullat the level
ofthe eyes.
Continued
Chapter 1 The Human Organism
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Part1 Organization ofthe Human Body4
Dynamicspatial reconstruction (DSR)
takesCT one step further. Instead of using
a single rotating x-raymachine to take sin-
gle slices and add them together, DSR
uses about 30 x-ray tubes. The images
from allthe tubes are compiled simultane-
ouslyto rapidly produce a 3-D image. Be-
cause of the speed of the process,
multiple imagescan be compiled to show
changesthrough time, thereby giving the
system a dynamicquality. This system al-
lows us to move away from seeing only
static structure and toward seeing dy-
namicstructure and function.
Digital subtraction angiography (an-
je¯-og⬘ra˘-fe¯) (DSA) is also one step beyond
CT scans. A 3-D radiographic image ofan
organ such asthe brain is made and stored
in a computer. A radiopaque dye is in-
jected into the circulation, and a second
radiographiccomputer image is made. The
first image is subtracted from the second
one, greatly enhancing the differences,
with the primarydifference being the pres-
ence of the injected dye (figure E). These
computer imagescan be dynamic and can
be used, for example, to guide a catheter
into a carotid artery during angioplasty,
which isthe insertion of a tiny balloon into
a carotid artery to compressmaterial clog-
ging the artery.
Magneticresonance imaging (MRI) di-
rectsradio waves at a person lying inside a
large electromagnetic field. The magnetic
field causesthe protons of various atoms to
align (see chapter 2). Because ofthe large
amounts of water in the body, the align-
ment ofhydrogen atom protons is at pres-
entmost important in this imaging system.
Radio waves of certain frequencies, which
change the alignment of the hydrogen
atoms, then are directed at the patient.
When the radio wavesare turned off, the hy-
drogen atomsrealign in accordance with the
magneticfield. The time it takes the hydro-
gen atomsto realign is different for various
tissues ofthe body. These differences can
be analyzed by computer to produce very
clear sections through the body (figure F).
The technique isalso very sensitive in de-
tecting some formsof cancer and can detect
a tumor far more readilythan can a CT scan.
Positron emission tomographic(PET)
scans can identify the metabolic states of
various tissues. This technique is particu-
larly useful in analyzing the brain. When
cellsare active, they are using energy. The
energythey need is supplied by the break-
down of glucose (blood sugar). Ifradioac-
tively treated, or “labeled,” glucose is
given to a patient, the active cellstake up
the labeled glucose. Asthe radioactivity in
the glucose decays, positively charged
subatomic particles called positrons are
emitted. When the positrons collide with
electrons, the two particlesannihilate each
other, and gamma raysare given off. The
gamma rayscan be detected, pinpointing
the cells that are metabolically active
(figure G).
Whenever the human bodyis exposed
to x-rays, ultrasound, electromagneticfields,
or radioactivelylabeled substances, a poten-
tialrisk exists. In the medical application of
anatomicimaging, the risk must be weighed
againstthe benefit. Numerous studies have
been conducted and are stillbeing done to
determine the outcomesof diagnostic and
therapeuticexposures to x-rays.
The risk of anatomicimaging is mini-
mized by using the lowest possible doses
thatprovide the necessary information. For
example, it is well known that x-rays can
cause celldamage, particularly to the repro-
ductive cells. Asa result of this knowledge,
the number ofx-rays and the level of expo-
sure are keptto a minimum, the x-ray beam
is focused as closely aspossible to avoid
scattering ofthe rays, areas of the body not
being x-rayed are shielded, and personnel
administering x-raysare shielded. No known
risks existfrom ultrasound or electromag-
neticfields at the levels used for diagnosis.
Figure E
DigitalSubtraction
Angiography(DSA)
Revealsthe major blood vessels supplying the
head and upper limbs.
Figure F
MagneticResonance
Imaging (MRI)
Showsa lateral view of the head and neck.
Figure G
Positron Emission
Tomography(PET)
Showsa transverse section through the skull.
The highestlevel of brain activity is indicated in
red, with successivelylower levels represented
byyellow, green, and blue.
(Continued)
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Chapter 1 The Human Organism 5
3. From smallest to largest, list and define the six levels at
which the bodycan be considered conceptually.
4. What are the four primary tissue types?
5. Which two organ systems are responsible for regulating the
otherorgan systems? Which two are responsible for
supportand movement?
6. What are the functions of the integumentary,
cardiovascular, lymphatic, respiratory, digestive, urinary,
and reproductive systems?
PREDICT
One type ofdiabetes is a disorder in which the pancreas (an organ)
failsto produce insulin, which is a chemicalnormally made by
pancreaticcells and released into the circulation. List asmany levels
oforganization as you can in which thisdisorder could be corrected.
The Human Organism
Objective
■ Listthe six characteristics of life, and give examples of how
theyapply to the human organism.
Characteristicsof Life
Humans are organisms and share common characteristics with
other organisms. The most important common feature of all or-
ganisms is life.Organization, metabolism, responsiveness, growth,
development,and reproduction are life’s essential characteristics.
Organization is the condition in which the parts of an or-
ganism have specific relationships to each other and the parts in-
teract to perform specific functions. Living things are highly
organized.All organisms are composed of one or more cells. Cells
in turn are composed of highly specialized organelles, which de-
pend on the precise organization oflarge molecules. Disruption of
this organized state can result in loss offunctions, and even death.
Metabolism(me˘-tab⬘o¯-lizm) is all ofthe chemical reactions
taking place in an organism.It includes the ability of an organism
to break down food molecules,which are used as a source of energy
and raw materials to synthesize the organism’s own molecules.En-
ergy is also used when one part of a molecule moves relative to an-
other part,resulting in a change in shape of the molecule. Changes
in molecular shape, in turn,can change the shape of cells, which
can produce movements ofthe organism. Metabolism is necessary
for vital functions, such as responsiveness,growth, development,
and reproduction.
Responsiveness is the abilit y of an organism to sense
changes in its external or internal environment and adjust to those
changes.Responses include such things as moving toward food or
water and away from danger or poor environmental conditions.
Organisms can also make adjustments that maintain their internal
environment.For example, if body temperature increases in a hot
environment,sweat glands produce sweat, which can lower body
temperature back toward normal levels.
Growth happens when cells increase in size or number,
which produces an overall enlargement ofall or part of an organ-
ism.For example, a muscle enlarged by exercise has larger muscle
cells than an untrained muscle,and the skin of an adult has more
Structural and Functional
Organization
Objectives
■ Describe and give examplesof the different levels of
organization of the body.
■ Listand give the functions of the 11 organ systems of the body.
Conceptually,the body has six structural levels: the chemical, cell,
tissue,organ, organ system, and complete organism (figure 1.1).
1. Chemical level.The chemical level involves interactions
between atoms,which are tiny building blocks of matter.
Atoms can combine to form molecules such as water,sugar,
fats,and proteins. The function of a molecule is related
intimately to its structure.For example, collagen molecules
are ropelike protein fibers that give skin structural strength
and flexibility.With old age,the str ucture of collagen
changes,and the skin becomes fragile and is torn more easily.
A briefoverview of chemistry is presented in chapter2.
2. Cell level.Cells are the basic units of all living things.
Molecules can combine to form organelles(or⬘ga˘-nelz),
which are the small structures that make up cells.For
example,the plasma membrane forms the outer boundary
ofthe cell and the nucleus contains the cell’s hereditary
information.Although cell types differ in their structure
and function,they have many characteristics in common.
Knowledge ofthese characteristics and their variations is
essential to a basic understanding ofanatomy and
physiology.The cell is discussed in chapter 3.
3. Tissue level.A tissue is a group of similar cells and the
materials surrounding them.The characteristics of the cells
and surrounding materials determine the functions ofthe
tissue.The numerous different tissues that make up the body
are classified into four basic types:epithelial, connective,
muscle,and nervous. Tissues are discussed in chapter 4.
4. Organ level.An organ is composed of two or more tissue
types that perform one or more common functions.The
urinary bladder,heart, skin, and eye are examples of organs
(figure 1.2).
5. Organ system level.An organ system is a group of organs
that have a common function or set offunctions and are
therefore viewed as a unit.For example, the urinary system
consists ofthe kidneys, ureter, urinary bladder, and urethra.
The kidneys produce urine,which is transported by the
ureters to the urinary bladder,where it is stored until
eliminated from the body by passing through the urethra.
In this text the body is considered to have 11 major organ
systems:the integumentary, skeletal, muscular,nervous,
endocrine,cardiovascular, lymphatic, respiratory,digestive,
urinary,and reproductive systems. Figure 1.3 presents a
briefsummar y of the organ systems and their functions.
6. Organism level.An organism is any living thing considered
as a whole,whether composed of one cell such as a
bacterium or oftr illions of cells such as a human.The
human organism is a complex oforgan systems, all
mutually dependent on one another.
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Part1 Organization ofthe Human Body6
1. Chemical level. Atoms
(
colored balls
) combine
to form molecules.
2. Cell level. Molecules
form organelles, such as
the plasma membrane and
nucleus, which make up
cells.
3. Tissue level. Similar cells
and surrounding materials
make up tissues.
4. Organ level. Different
tissues combine to form
organs, such as the
urinary bladder.
5. Organ system level.
Organs such as the
urinary bladder and
kidneys make up an
organ system.
6. Organism level. Organ
systems make up an
organism.
Kidney
Ureter
Urinary bladder
Urethra
Urinary system
Urinary
bladder
Smooth
muscle
tissue
Smooth muscle cell
Plasma
membrane
Nucleus
Molecule
(DNA)
Atoms
Epithelium
Connective tissue
Connective tissue
Smooth muscle tissue
Organism
Wall of urinary bladder
1
2
3
4
5
6
Figure 1.1
Levelsof Organization
Sixlevels of organization for the human body are the chemical, cell, tissue, organ, organ system, and organism.
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
cells than the skin of infant. An increase in the materials
surrounding cells can also contribute to growth.For instance, the
growth of bone results from an increase in cell number and the
deposition ofmineralized materials around the cells.
Developmentincludes the changes an organism undergoes
through time; it begins with fertilization and ends at death. The
greatest developmental changes occur before birth, but many
changes continue after birth,and some continue throughout life. De-
velopment usually involves growth,but it also involves differentiation
and morphogenesis. Differentiation is change in cell structure
and function from generalized to specialized,and morphogenesis
(mo¯r-fo¯-jen⬘e˘-sis) is change in the shape oftissues, organs,and the
entire organism.For example,following fer tilization,generalized cells
specialize to become specific cell types,such as skin, bone, muscle,
or nerve cells.These differentiated cells form the tissues and organs.
Reproductionis the formation of new cells or new organisms.
Without reproduction,growth and development are not possible.
Without reproduction ofthe organism, species become extinct.
BiomedicalResearch
Studying other organisms has increased our knowledge about hu-
mans because humans share many characteristics with other or-
ganisms. For example, studying single-celled bacteria provides
much information about human cells.Some biomedical research,
however,cannot be accomplished using single-celled organisms or
Chapter 1 The Human Organism 7
isolated cells.Sometimes other mammals must be studied. For ex-
ample,great progress in open-heart surgery and kidney transplan-
tation was made possible by perfecting surgical techniques on
other mammals before attempting them on humans. Strict laws
govern the use of animals in biomedical research—laws designed
to ensure minimum suffering on the part ofthe animal and to dis-
courage unnecessary experimentation.
Although much can be learned from studying other organ-
isms,the ultimate answers to questions about humans can be ob-
tained only from humans, because other organisms are often
different from humans in significant ways.
Small intestine
Kidney
(behind stomach)
Stomach
Spleen (behind stomach)
Diaphragm
Trachea
Larynx
Brain
Spinal cord
Esophagus
Carotid
artery
Aortic arch
Lung
Heart
Liver
Kidney
(behind intestine)
Pancreas (behind
stomach)
Gallbladder
Large
intestine
Ureter
(behind small
intestine)
Urinary
bladder
Urethra
Figure 1.2
Organsof the Body
Human VersusAnimal-Based Knowledge
Failure to appreciate the differencesbetween humans and other animals
led to manymisconceptions by early scientists. One ofthe first great
anatomistswas a Greek physician, ClaudiusGalen (ca. 130–201). Galen
described a large number ofanatomic structures supposedly present in
humansbut observed only in other animals. For example, he described
the liver ashaving five lobes. This is true for rats, but notfor humans,
who have four-lobed livers. The errorsintroduced by Galen persisted for
more than 1300 yearsuntil a Flemish anatomist, AndreasVesalius
(1514–1564), who isconsidered the first modern anatomist, carefully
examined human cadaversand began to correct the textbooks. This
example should serve asa word of caution: Some current knowledge in
molecular biologyand physiology has not been confirmed in humans.
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Part1 Organization ofthe Human Body8
Figure 1.3
Organ Systemsof the Body
IntegumentarySystem
Providesprotection, regulates temperature,
preventswater loss, and produces vitamin D
precursors. Consistsof skin, hair, nails, and
sweatglands.
SkeletalSystem
Providesprotection and support, allows
bodymovements, produces blood cells, and
storesminerals and fat. Consists of bones,
associated cartilages, ligaments, and joints.
Muscular System
Producesbody movements, maintains
posture, and producesbody heat. Consists
ofmuscles attached to the skeleton by
tendons.
LymphaticSystem
Removesforeign substances from the blood
and lymph, combatsdisease, maintains
tissue fluid balance, and absorbsfats from
the digestive tract. Consistsof the lymphatic
vessels, lymph nodes, and other lymphatic
organs.
RespiratorySystem
Exchangesoxygen and carbon dioxide
between the blood and air and regulates
blood pH. Consistsof the lungsand
respiratorypassages.
Digestive System
Performsthe mechanical and chemical
processesof digestion, absorption of
nutrients, and elimination ofwastes.
Consistsof the mouth, esophagus,
stomach, intestines, and accessoryorgans.
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Figure 1.3
(continued)
Chapter 1 The Human Organism 9
NervousSystem
A major regulatorysystem that detects
sensationsand controls movements,
physiologicprocesses, and intellectual
functions. Consistsofthe brain, spinal cord,
nerves, and sensoryreceptors.
Endocrine System
A major regulatorysystem that influences
metabolism, growth, reproduction, and
manyother functions. Consists ofglands,
such asthe pituitary, that secrete hormones.
Cardiovascular System
Transportsnutrients, waste products, gases,
and hormonesthroughout the body; plays a
role in the immune response and the
regulation ofbody temperature. Consistsof
the heart, blood vessels, and blood.
UrinarySystem
Removeswaste products from the blood
and regulatesblood pH, ion balance, and
water balance. Consistsofthe kidneys,
urinarybladder, and ducts that carry urine.
Female Reproductive System
Producesoocytes and is the site of
fertilization and fetaldevelopment;
producesmilk for the newborn; produces
hormonesthat influence sexual functions
and behaviors. Consistsof the ovaries,
vagina, uterus, mammaryglands, and
associated structures.
Male Reproductive System
Producesand transfers sperm cells to the
female and produceshormones that
influence sexualfunctions and behaviors.
Consistsof the testes, accessorystructures,
ducts, and penis.
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
7. Describe six characteristics of life.
8. Why is it important to realize that humans share many, but
notall, characteristics with other animals?
Homeostasis
Objective
■ Define homeostasis. Give examplesof negative-feedback
and positive-feedbackmechanisms and explain their
relationship to homeostasis.
Homeostasis (ho¯⬘me¯-o¯-sta¯⬘sis) is the existence and maintenance
of a relatively constant environment within the body.A small
amount offluid sur rounds each cell of the body.For cells to func-
tion normally,the volume, temperature, and chemical content—
conditions known as variables because their values can
Part1 Organization ofthe Human Body10
Normal range
Set point
Time
Figure 1.4
Homeostasis
Homeostasisis the maintenance ofa variable around an ideal normal value,
or setpoint. The value of the variable fluctuates around the setpoint to
establish a normalrange of values.
Normal range
A control center responds to
information from the receptor.
The activity of an effector changes.
An increase in the variable is
detected by a receptor.
Value increases
Value decreases
A decrease in the variable is caused by
the response of the effector.
A decrease in the variable is
detected by a receptor.
An increase in the variable is caused
by the response of the effector.
A control center responds to
information from the receptor.
The activity of an effector changes.
Normal range
Homeostasis
is maintained
3
4
6
5
2
7
1
HomeostasisFigure 1.5
Mechanism ofNegative Feedback
Throughoutthe text, all homeostasis figures have the same formatas in this figure. The changes caused by an increase of a variable are shown in the green boxes,
and the changescaused by a decrease are shown in the red boxes.To help you learn how to interpret homeostasis figures, some of the stepsin this figure are
numbered: (1) The variable iswithin its normal range. (2) The value ofthe variable increases and is outside its normal range. (3) The increase in the variable is
detected byreceptors. (4) The control center responds to the change in the variable detected bythe receptors. (5) The control center causes the activity of the
effector to change. (6) The change in effector activitycausesthe value of the variable to decrease. (7) The variable returns to its normal range and homeostasisis
maintained. See the responsesto a decrease of the variable byfollowing the red boxes.
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Chapter 1 The Human Organism 11
change—of this fluid must remain within a narrow range. Body
temperature is a variable that can increase in a hot environment or
decrease in a cold one.
Homeostatic mechanisms, such as sweating or shivering,
normally maintain body temperature near an ideal normal value,
orset point (figure 1.4).Note that these mechanisms are not able
to maintain body temperature precisely at the set point.Instead,
body temperature increases and decreases slightly around the set
point to produce a normal range of values. As long as body
temperature remains within this normal range, homeostasis
ismaintained.
The organ systems help control the body’s internal environ-
ment so that it remains relatively constant.For example, the diges-
tive,respiratory,circulator y,and urinary systems function together
so that each cell in the body receives adequate oxygen and nutrients
and so that waste products do not accumulate to a toxic level.If the
fluid surrounding cells deviates from homeostasis,the cells do not
function normally and can even die.Disruption of homeostasis re-
sults in disease and sometimes death.
Negative Feedback
Most systems of the body are regulated by negative-feedback
mechanisms that maintain homeostasis.Ne gativ e means that any
deviation from the set point is made smaller or is resisted.Many
negative-feedback mechanisms have three components:a receptor,
which monitors the value ofsome variable such as blood pressure;
acontrol center, which establishes the set point around which the
variable is maintained;and an effector, which can change the value
ofthe variable. A deviation from the set point is called a stimulus.
The receptor detects the stimulus and informs the control center,
which analyzes the input from the receptor.The control center sends
output to the effector,and the effector produces a response,which
tends to return the variable back toward the set point (figure 1.5).
The maintenance ofnormal blood pressure is an example of
a negative-feedback mechanism that maintains homeostasis (fig-
ure 1.6).Normal blood pressure is important because it is respon-
sible for moving blood from the heart to tissues. The blood
supplies the tissues with oxygen and nutrients and removes waste
products. Thus normal blood pressure is required to ensure that
tissue homeostasis ismaintained.
Blood pressure
(normal range)
Blood pressure
increases
Blood pressure
decreases
Blood pressure
(normal range)
Blood pressure
homeostasis
is maintained
The control center in the brain that
regulates heart rate responds.
The heart rate decreases.
An increase in blood pressure is detected
by receptors in blood vessels.
A decrease in blood pressure is caused by
a decrease in heart rate.
A decrease in blood pressure is detected
by receptors in blood vessels.
An increase in blood pressure is caused
by an increase in heart rate.
The control center in the brain that
regulates heart rate responds.
The heart rate increases.
HomeostasisFigure 1.6
Example ofNegative Feedback
Blood pressure ismaintained within a normal range bynegative-feedback mechanisms.
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Receptors that monitor blood pressure are located within large
blood vessels near the heart,the control center for blood pressure is in
the brain,and the heart is the effector.Blood pressure depends in part
on contraction (beating) of the heart: as heart rate increases, blood
pressure increases;as heart rate decreases, blood pressure decreases.
If blood pressure increases slightly,the receptors detect the
increased blood pressure and send that information to the control
center in the brain.The control center causes heart rate to decrease,
resulting in a decrease in blood pressure. If blood pressure de-
creases slightly,the receptors inform the control center, which in-
creases heart rate,thereby producing an increase in blood pressure.
As a result,blood pressure constantly rises and falls within a nor-
mal range ofvalues.
Although homeostasis is the maintenance ofa normal range of
values,this does not mean that all variables are maintained within the
same narrow range ofvalues at all times. Sometimes a deviation from
the usual range ofvalues can be beneficial. For example, during exer-
cise the normal range for blood pressure differs from the range under
resting conditions, and the blood pressure is significantly elevated
(figure 1.7).The elevated blood pressure increases blood delivery to
muscles so that muscle cells are supplied with the extra nutrients and
oxygen they need to maintain their increased rate ofactivity.
9. Define homeostasis, variable, and set point. If a deviation
from homeostasisoccurs, what mechanism restores it?
10. What are the three components of many negative-feedback
mechanisms? Howdo they produce a response to a
stimulus?
Part1 Organization ofthe Human Body12
PREDICT
Explain how negative-feedbackmechanismscontrol respiratory rates
when a person isat rest and when a person is exercising.
Positive Feedback
Positive-feedbackresponses are not homeostatic and are rare in
healthy individuals.Positive implies that, when a deviation from a
normal value occurs,the response of the system is to make the de-
viation even greater (figure 1.8).Positive feedback therefore usually
creates a cycle that leads away from homeostasis and,in some cases,
results in death.
The cardiac (heart) muscle receiving an inadequate amount
ofblood is an example of positive feedback. Contraction of cardiac
muscle generates blood pressure and moves blood through blood
vessels to tissues.A system of blood vessels on the outside of the
heart provides cardiac muscle with a blood supply sufficient to al-
low normal contractions to occur.In effect,the hear t pumps blood
to itself.Just as with other tissues, blood pressure must be main-
tained to ensure adequate delivery ofblood to cardiac muscle. Fol-
lowing extreme blood loss,blood pressure decreases to the point
that delivery of blood to cardiac muscle is inadequate.As a result,
cardiac muscle homeostasis is disrupted,and cardiac muscle does
not function normally.The heart pumps less blood, which causes
the blood pressure to drop even further.This additional decrease in
blood pressure means that even less blood is delivered to cardiac
muscle, and the heart pumps even less blood, which again de-
creases the blood pressure (figure 1.9). If the process continues
until the blood pressure is too low to sustain the cardiac muscle,
the heart stops beating,and death results.
Normal range
Constantly increasing value
outside of the normal range
Homeostasis is
not maintained
Constantly decreasing value
outside of the normal range
Time
Figure 1.8
Positive Feedback
Deviationsfrom the normal set point value cause an additionaldeviation away
from thatvalue in either a positive or negative direction.
Blood pressure
Time
Normal BP at rest Normal BP
after exercise
Normal BP
during exercise
Figure 1.7
Changesin Blood Pressure During Exercise
During exercise the demand for oxygen bymuscle tissue increases. An
increase in blood pressure (BP) resultsin an increase in blood flow to the
tissues. The increased blood pressure isnot an abnormalor nonhomeostatic
condition butis a resetting of the normal homeostatic range to meetthe
increased demand. The resetrange is higher and broader than the resting
range. After exercise ceases, the range returnsto thatof the resting condition.
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Chapter 1 The Human Organism 13
Following a moderate amount ofblood loss (e.g., after a per-
son donates a pint of blood),negative-feedback mechanisms pro-
duce an increase in heart rate and other responses that restore blood
pressure.If blood loss is severe, however,negative-feedback mech-
anisms may not be able to maintain homeostasis,and the positive-
feedback effect of an ever-decreasing blood pressure can develop.
Circumstances in which negative-feedback mechanisms are not
adequate to maintain homeostasis illustrate a basic principle.Many
disease states result from failure ofnegative-feedback mechanisms
to maintain homeostasis.Medical therapy seeks to overcome illness
by aiding negative-feedback mechanisms (e.g.,a transfusion reverses
a constantly decreasing blood pressure and restores homeostasis).
A few positive-feedback mechanisms do operate in the
body under normal conditions,but in all cases they are eventu-
ally limited in some way. Birth is an example of a normally
occurring positive-feedback mechanism.Near the end of preg-
nancy,the baby’s larger size stretches the uterus.This stretching,
especially around the opening of the uterus,stimulates contrac-
tions of the uterine muscles. The uterine contractions push the
baby against the opening of the uterus and stretch it further.
This stimulates additional contractions that result in additional
stretching.This positive-feedback sequence ends only when the
baby is delivered from the uterus and the stretching stimulus is
eliminated.
11. Define positive feedback. Why are positive-feedback
mechanismsoften harmful?
PREDICT
Isthe sensation of thirst associated with a negative- or a positive-
feedbackmechanism? Explain.
Terminologyand the Body Plan
Objectives
■ Define the anatomicposition and its importance to
directional terms.
■ Identifyand define the directional terms, parts, and planes
of the body.
■ Name the majortrunk cavities and describe the serous
membranesassociated with each of them.
You will be learning many new words as you study anatomy and
physiology.Knowing the derivation, or etymology (et⬘uh-mol⬘˘o-j¯e),
of these words,can make learning them easy and fun. Most words
are derived from Latin or Greek,which are very descriptive lan-
guages.For example, foramen is a Latin word for hole,and magnum
means large.The foramen magnum is therefore a large hole in the
skull through which the spinal cord attaches to the brain.
Prefixes and suffixes can be added to words to expand their
meaning.The suffix -itis means an inflammation,so appendicitis
is an inflammation of the appendix.As new terms are introduced
in this text,their meanings are often explained. The glossary and
the list of word roots, prefixes,and suffixes on the inside back
cover of the textbook provide additional information about the
new terms.
It is very important to learn these new words so that when
you speak to colleagues or write reports your message is clear
andcorrect.
Body Positions
Theanatomic position refers to a person standing erect with the
face directed forward,the upper limbs hanging to the sides, and
the palms of the hands facing forward (figure 1.10).A person is
supine when lying face upward and prone when lying face
downward.
The position of the body can affect the description of body
parts relative to each other.In the anatomic position, the elbow is
above the hand,but in the supine or prone position, the elbow and
hand are at the same level.To avoid confusion, relational descrip-
tions are always based on the anatomic position,no matter the ac-
tual position of the body.Thus, the elbow is always described as
being above the wrist,whether the person is lying down or is even
upside down.
DirectionalTerms
Directional terms describe parts of the body relative to each
other. Important directional terms are illustrated in figure 1.9
and summarized in table 1.1.It is important to become familiar
with these directional terms as soon as possible because you will
see them repeatedly throughout the text. Right and left are
Blood pressure
(normal range)
Blood pressure
decreases below normal
Blood flow to cardiac
muscle decreases
Blood pressure
decreases even more
Figure 1.9
Example ofHarmful Positive Feedback
A decrease in blood pressure below the normalrange causes decreased blood
flow to the heart. The heartis unable to pump enough blood to maintain blood
pressure, and blood flow to the cardiacmuscle decreases. Thus the ability of
the heartto pump decreases further, and blood pressure decreases even more.
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retained as directional terms in anatomic terminology.Up is re-
placed by superior,down by infer ior, front by anterior, and
back by posterior.
In humans,superior is synonymous with cephalic (se-fal⬘ik),
which means toward the head, because, when we are in the
anatomic position, the head is the highest point.In humans, the
term inferior is synonymous with caudal (kaw⬘da˘l),which means
toward the tail,which would be located at the end of the vertebral
column ifhumans had tails. The terms cephalic and caudalcan be
used to describe directional movements on the trunk,but they are
not used to describe directional movements on the limbs.
The word anteriormeans that which goes before, and ventral
means belly.The anterior surface of the human body is therefore
the ventral surface,or belly, because the belly “goes first”when we
are walking. The word posterior means that which follows, and
dorsalmeans back. The posterior surface of the body is the dorsal
surface,or back, which follows as we are walking.
Part1 Organization ofthe Human Body14
12. What is the anatomic position in humans? Why is it
important?
13. List two terms that in humans indicate toward the head.
Name two termsthat mean the opposite.
14. List two terms that indicate the back in humans. What two
termsmean the front?
PREDICT
The anatomicposition of a cat refers to the animal standing erecton
allfour limbs and facing forward. On the basiso fthe etymolog yof the
directionalterms, what two terms indicate movement toward the
head? Whattwo terms mean movement toward the back? Compare
these termsto those referring to a human in the anatomic position.
Proximal means nearest, whereas distal means distant.
These terms are used to refer to linear structures,such as the limbs,
in which one end is near some other structure and the other end is
Right
Left
Superior
(Cephalic)
Proximal
Midline
Inferior
(Caudal)
Distal
Proximal
Medial
Lateral
Distal
Superior
(Cephalic)
Inferior
(Caudal)
Proximal
Distal
Anterior
Posterior
(Ventral)
(Dorsal)
Figure 1.10
DirectionalTerms
Alldirectional terms are in relation to a person in the anatomic position: a person standing erect with the face directed forward, the armshanging to the sides, and
the palmsof the hands facing forward.
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Chapter 1 The Human Organism 15
farther away.Each limb is attached at its proximal end to the body,
and the distal end,such as the hand, is farther away.
Medialmeans toward the midline, and lateral means away
from the midline.The nose is located in a medial position in the
face, and the eyes are lateral to the nose.The term sup erficial
refers to a structure close to the surface of the body,and deep is
toward the interior of the body.The skin is superficial to muscle
and bone.
15. Define the following terms, and give the word that means
the opposite: proximal, lateral, and superficial.
PREDICT
Describe in asmany directional terms as you can the relationship
between your kneecap and your heel.
Body Partsand Regions
A number of terms are used when referring to different parts or
regions of the body (figure 1.11).The upper limb is divided into
the arm, forearm, wrist, and hand. The arm extends from the
shoulder to the elbow,and the forearm extends from the elbow
to the wrist.The lower limb is divided into the thigh, leg, ankle,
and foot.The thigh extends from the hip to the knee, and the leg
extends from the knee to the ankle.Note that, contrary to popu-
lar usage, the terms arm and leg refer to only a part of the
respective limb.
The central region of the body consists of the head, neck,
andtr unk. The trunk can be divided into the thorax (chest), ab-
domen(region between the thorax and pelvis), and pelvis (the in-
ferior end ofthe tr unk associated with the hips).
The abdomen is often subdivided superficially into quad-
rantsby two imaginary lines—one horizontal and one vertical—
that intersect at the navel (figure 1.12a).The quadrants for med
are the right-upper,left-upper, right-lower, and left-lower quad-
rants.In addition to these quadrants, the abdomen is sometimes
subdivided into nine regions by four imaginary lines: two hori-
zontal and two vertical.These four lines create an imaginary tic-
tac-toe figure on the abdomen, resulting in nine regions:
epigastric, right and left hypochondriac,umbilical, right and left
lumbar,hypogastric, and right and left iliac (figure 1.12b). Clini-
cians use the quadrants or regions as reference points for locating
underlying organs. For example, the appendix is located in the
Table 1.1
Terms Etymology* Definition Example
Right Toward the right side of the body The right ear.
Left Toward the left side of the body The left eye.
Superior L., higher A structure above another The chin is superior to the navel.
Inferior L., lower A structure below another The navel is inferior to the chin.
Cephalic G. kephale,head Closer to the head than another The chin is cephalic to the navel.
structure (usually synonymous with superior)
Caudal L. cauda, a tail Closer to the tail than another The navel is caudal to the chin.
structure (usually synonymous with inferior)
Anterior L., before The front of the body The navel is anterior to the spine.
Posterior L. posterus, following The back of the body The spine is posterior to the breastbone.
Ventral L. ventr-, belly Toward the belly (synonymous with anterior) The navel is ventral to the spine.
Dorsal L. dorsum,back Toward the back (synonymous with posterior) The spine is dorsal to the breastbone.
Proximal L. proximus, nearest Closer to the point of attachment The elbow is proximal to the wrist.
to the body than another structure
Distal L. di- plus sto, to stand apart Farther from the point of attachment The wrist is distal to the elbow.
or be distant to the body than another structure
Lateral L. latus,side Away from the midline of the body The nipple is lateral to the breastbone.
Medial L. medialis, middle Toward the midline of the body The bridge of the nose is medial to the eye.
Superficial L. superficialis, Toward or on the surface The skin is superficial to muscle.
toward the surface (not shown in figure 1.10)
Deep O.E. deop, deep Away from the surface, internal The lungs are deep to the ribs.
(not shown in figure 1.10)
Directional Terms for Humans
*Origin and meaning of the word: L., Latin; G., Greek; O.E., Old English.
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right-lower quadrant,and the pain of an acute appendicitis is usu-
ally felt there.
16. What is the difference between the arm and the upper
limb and the difference between the leg and the lower
limb?
17. Describe the quadrant and the nine-region methods of
subdividing the abdominal region. Whatis the purpose of
these subdivisions?
PREDICT
Using figures1.2 (p. 7) and 1.12 (p. 18), determine in which quadrant
each ofthe following organs is located: spleen, gallbladder, kidneys,
mostof the stomach, and most of the liver.
Part1 Organization ofthe Human Body16
Planes
At times it is conceptually useful to describe the body as having
imaginary flat surfaces called planes passing through it (figure
1.13).A plane divides or sections the body, making it possible to
“look inside” and observe the body’s structures. A sagittal
(saj⬘i-ta˘l) plane runs vertically through the body and separates it
into right and left portions.The word sagittal literally means “the
flight ofan arrow” and refers to the way the body would be split by
an arrow passing anteriorly to posteriorly.A midsagittal, or a me-
dian,plane divides the body into equal right and left halves, and a
parasagittalplane runs vertically through the body to one side of
the midline.A transverse, or horizontal, plane runs parallel to
the ground and divides the body into superior and inferior por-
tions. A frontal, or coronal (ko¯r⬘o˘-na˘l,ko¯-ro¯⬘na˘l),plane runs
Figure 1.11
BodyParts and Regions
The common and anatomic(in parentheses) names are indicated for some parts and regions of the body. (a) Anterior view.
Head
(cephalic)
or skull
(cranium)
Thorax
(thoracic)
Trunk
Upper limb
Lower limb
Forehead (frontal)
Eye (orbital)
Nose (nasal)
Mouth (oral)
Neck (cervical)
Chest (pectoral)
Breastbone (sternal)
Breast (mammary)
Abdomen (abdominal)
Navel (umbilical)
Pelvis (pelvic)
Groin (inguinal)
Genital region (pubic)
Chin (mental)
Collar bone (clavicular)
Arm pit (axillary)
Shoulder
Arm (brachial)
Elbow (cubital)
Forearm (antebrachial)
Wrist (carpal)
Palm (palmar)
Fingers (digital)
Hip (coxal)
Thigh (femoral)
Kneecap (patellar)
Leg (crural)
Ankle
Top of foot (dorsum)
Toes (digital)
Cheek (buccal)
Ear (otic)
Foot (pedal)
Hand (manual)
(a)
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Chapter 1 The Human Organism 17
vertically from right to left and divides the body into anterior and
posterior parts.
Organs are often sectioned to reveal their internal structure
(figure 1.14).A cut through the long axis of the organ is a longitu-
dinalsection, and a cut at right angles to the long axis is a cross, or
transverse, section. If a cut is made across the long axis at other
than a right angle,it is called an oblique section.
18. Define the three planes of the body. What is the difference
between a parasagittal section and a midsagittal section?
19. In what three ways can an organ be cut?
Body Cavities
The body contains many cavities,among which are the nasal, cra-
nial,and abdominal cavities. Some of these open to the outside of
the body,and some do not. Introductory anatomy and physiology
textbooks sometimes describe a dorsal cavity,in which the brain and
spinal cord are found,and a ventral body cavity that contains all the
trunk cavities.The concept of a dorsal cavity is not described in stan-
dard works on anatomy.No embryonic,anatomic, or histologic par-
allels exist between the fluid-filled space around the central nervous
system and the trunk cavities.Discussion in this chapter is therefore
limited to the major trunk cavities that do not open to the outside.
The trunk contains three large cavities:the thoracic, the ab-
dominal,and the pelvic (figure 1.15). The rib cage surrounds the
thoracic cavity,and the muscular diaphragm separates it from the
abdominal cavity.The thoracic cavity is divided into right and left
parts by a median partition called the mediastinum (me⬘de¯-as-
tı¯⬘nu˘m;middle wall). The mediastinum contains the heart, thy-
mus gland,trachea, esophagus, and other structures such as blood
Shoulder blade (scapular)
Spinal column (vertebral)
Back of neck (nuchal)
Base of skull (occipital)
Back
(dosal)
Trunk
Upper limb
Lower limb
Loin (lumbar)
Between hips (sacral)
Buttock (gluteal)
Perineum (perineal)
Point of shoulder (acromion)
Point of elbow (olecranon)
Back of hand (dorsum)
Hollow behind knee (popliteal)
Calf (sural)
Sole (plantar)
Heel (calcaneal)
Figure 1.11
(continued)
(b) Posterior view.
(b)
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vessels and nerves. The two lungs are located on either side of
themediastinum.
Abdominal muscles primarily enclose the abdominal cavity,
which contains the stomach,intestines, liver,spleen, pancreas, and
kidneys.Pelvic bones encase the small space known as the pelvic
cavity,where the urinar y bladder,part of the large intestine, and
the internal reproductive organs are housed.The abdominal and
pelvic cavities are not physically separated and sometimes are
called the abdominopelvic cavity.
SerousMembranes
Serous(se¯r⬘u˘s)membranes cover the organs of the trunk cavities
and line the trunk cavities.Imagine an inflated balloon into which
a fist has been pushed (figure 1.16).The fist represents an organ,
the inner balloon wall in contact with the fist represents the vis-
ceral(vis⬘er-a˘l;organ)serous membrane covering the organ, and
the outer part of the balloon wall represents the parietal
(pa˘-rı¯⬘e˘-ta˘l;wall) serous membr ane. The cavity or space be-
tween the visceral and parietal serous membranes is normally
filled with a thin,lubricating film of serous fluid produced by the
membranes. As organs rub against the body wall or against an-
other organ,the combination of serous fluid and smooth serous
membranes reduces friction. The thoracic cavity contains three
serous membrane-lined cavities: a pericardial cavity and two
pleural cavities.
Part1 Organization ofthe Human Body18
Thepericardial (per-i-kar⬘de¯-a˘l;around the heart) cavity sur-
rounds the heart (figure 1.17a).The visceral pericardium covers the
heart,which is contained within a connective tissue sac lined with the
parietal pericardium.The pericardial cavity, which contains pericar-
dial fluid,is located between the visceral and parietal pericardia.
A pleural (ploor⬘a˘ l; associated with the ribs) cavity sur-
rounds each lung, which is covered by visceral pleura (figure
1.17b). Parietal pleura line the inner surface of the thoracic wall,
the lateral surfaces ofthe mediastinum, and the superior surface of
the diaphragm. The pleural cavity lies between the visceral and
parietal pleurae and contains pleural fluid.
The abdominopelvic cavity contains a serous membrane-
lined cavity called the peritoneal(per⬘i-to¯-ne¯⬘a˘l; to stretch over)
cavity (figure 1.17c). Visceral peritoneum covers many of the
organs ofthe abdominopelvic cavity. Parietal peritoneum lines the
wall of the abdominopelvic cavity and the inferior surface of the
diaphragm. The peritoneal cavity is located between the visceral
and parietal peritonea and contains peritoneal fluid.
Inflammation ofSerous Membranes
The serousmembranes can become inflamed, usually as a result of an
infection.Pericarditis (per⬘i-kar-dı¯⬘tis) isinflammation ofthe
pericardium, pleurisy(ploor⬘i-se¯) isinflammation ofthe pleura, and
peritonitis(per⬘i-to¯-nı¯⬘tis) is inflammation of the peritoneum.
Right-upper
quadrant
Left-upper
quadrant
Right-lower
quadrant
Left-lower
quadrant
Right
hypochondriac
region
Left
hypochondriac
region
Epigastric
region
Right
lumbar
region
Umbilical
region
Left
lumbar
region
Right
iliac
region
Hypogastric
region
Left
iliac
region
Figure 1.12
Subdivisionsof the Abdomen
Linesare superimposed over internal organs to demonstrate the relationship ofthe organs to the subdivisions. (a) Abdominal quadrants consist of four
subdivisions. (b) Abdominalregions consistof nine subdivisions.
(b)
(a)
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Chapter 1 The Human Organism 19
Midsagittal
plane
Parasagittal
plane
Cerebrum
Transverse
or horizontal,
plane
Frontal, or
coronal, plane
Cerebellum
Brainstem
Spinal cord
Vertebral
column
Nasal cavity
Tongue
Pharynx (throat)
Trachea
Midsagittal section of the head
Frontal section through the right hip Transverse section through the abdomen
Liver
Skin
Fat
Kidney
Spinal
cord
Stomach
Large
intestine
Spleen
Vertebra
Kidney
Hip muscle
Femur
(thighbone)
Coxa
(hipbone)
Thigh muscles
Figure 1.13
Planesof Section of the Body
Planesof section through the whole body are indicated by “glass” sheets.
Actualsections through the head, hip, and abdomen are also shown.
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Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Part1 Organization ofthe Human Body20
Longitudinal section
Transverse
section
Oblique
section
Intestine
Figure 1.14
Planesof Section Through an Organ
Planesof section through the small intestine are indicated by “glass” sheets.
The viewsof the small intestine after sectioning are also shown. Although the
smallintestine is basically a tube, the sectionsappear quite different in shape.
Trachea
Esophagus
Heart
Thymus
Blood vessels
Mediastinum
(divides
thoracic
cavity)
Abdominopelvic
cavity
Abdominal
cavity
Diaphragm
Thoracic
cavity
Abdominal
cavity
Pelvic
cavity
Pelvic cavity
Figure 1.15
TrunkCavities
(a) Anterior view showing the major trunkcavities. The diaphragm separatesthe thoracic cavity from the abdominal cavity. The mediastinum, which includesthe
heart, isa partition of organs dividing the thoracic cavity. (b) Sagittalview of trunk cavities. The dashed line shows the division between the abdominal and pelvic
cavities. The mediastinum hasbeen removed to show the thoraciccavity.
Mesenteries(mes⬘en-ter-e¯z),which consist of two layers of
peritoneum fused together (see figure 1.17c),connect the visceral
peritoneum of some abdominopelvic organs to the parietal peri-
toneum on the body wall or to the visceral peritoneum ofother ab-
dominopelvic organs. The mesenteries anchor the organs to the
body wall and provide a pathway for nerves and blood vessels to
reach the organs.Other abdominopelv ic organs are more closely
attached to the body wall and do not have mesenteries. Parietal
peritoneum covers these other organs which are said to be
retroperitoneal (re⬘tro¯-per⬘i-to¯-ne¯⬘a˘ l; behind the peritoneum).
The retroperitoneal organs include the kidneys,the adrenal glands,
the pancreas,parts of the intestines,and the urinar y bladder (see
figure 1.17c).
20. Define serous membranes. Differentiate between parietal
and visceral serousmembranes. What isthe function of the
serousmembranes?
21. Name the serous membranes lining each of the trunk
cavities.
22. What are mesenteries? Explain their function.
23. What are retroperitoneal organs? List four examples.
PREDICT
Explain how an organ can be located within the abdominopelviccavity
butnot be within the peritoneal cavity.
(a) (b)
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Chapter 1 The Human Organism 21
Figure 1.16
SerousMembranes
(a) Fistpushing into a balloon. A “glass” sheet indicates the location of a crosssection through the balloon. (b) Interior view produced by the section in (a). The fist
representsan organ, and the walls of the balloon the serous membranes. The inner wallof the balloon represents a visceral serous membrane in contact with the
fist(organ). The outer wall of the balloon represents a parietalserous membrane.
Outer balloon wall
Inner balloon wall
Cavity
Fist
Outer balloon wall
(parietal serous
membrane)
Inner balloon wall
(visceral serous
membrane)
Cavity
Fist
Figure 1.17
Location ofSerous Membranes
(a) Frontalsection showing the parietal pericardium (blue), visceral
pericardium (red), and pericardialcavity. (b) Frontal section showing the
parietalpleural (blue), visceralpleural (red), and pleural cavities. (c) Sagittal
section through the abdominopelviccavity showing the parietal peritoneum
(blue), visceralperitoneum (red), peritoneal cavity, mesenteries(purple), and
retroperitonealorgans.
Parietal
pericardium
Visceral
pericardium
Pericardial
cavity
containing
pericardial
fluid
Heart
Parietal
pleura
Visceral
pleura
Pleural cavity containing
pleural fluid
Diaphragm
Lung
Retroperitoneal
organs
Parietal
peritoneum
Visceral
peritoneum
Peritoneal
cavity
containing
peritoneal
fluid
Retroperitoneal
organs
Mesentery
Organ
surrounded
by visceral
peritoneum
(b)
(a)
(a)
(b)
(c)
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Part1 Organization ofthe Human Body22
A functional knowledge of anatomy and physiology can be used to solve
problems concerning the body when healthy or diseased.
Anatomyand Physiology
(p. 2)
1. Anatomy is the study ofthe body’s structures.
• Developmental anatomy considers anatomic changes from
conception to adulthood.Embryology focuses on the first eight
weeks ofdevelopment.
• Cytology examines cells, and histology examines tissues.
• Gross anatomy emphasizes organs from a systemic or regional
perspective.
2. Surface anatomy uses superficial structures to locate deeper
structures,and anatomic imaging is a noninvasive technique for
identifying deep structures.
3. Physiology is the study ofthe body’s functions. It can be approached
from a cellular or systems point ofview.
4. Pathology deals with all aspects ofdisease. Exercise physiology
examines changes caused by exercise.
Structuraland Functional Organization
(p. 5)
1. Basic chemical characteristics are responsible for the structure and
functions oflife.
2. Cells are the basic living units ofplants and animals and have many
common characteristics.Organelles are small structures within cells
that perform specific functions.
3. Tissues are groups ofcells of similar structure and function and the
materials surrounding them.The four primary tissue types are
epithelial,connective, muscle, and nervous tissues.
4. Organs are structures composed oftwo or more tissues that perform
specific functions.
5. Organs are arranged into the 11 organ systems ofthe human body
(see figure 1.2).
6. Organ systems interact to form a whole,functioning organism.
The Human Organism
(p. 5)
Characteristicsof Life
Humans have many characteristics such as organization,metabolism, re-
sponsiveness,g rowth,development, and reproduction in common with
other organisms.
BiomedicalResearch
Much ofwhat is known about humans is derived from research on other
organisms.
Homeostasis
(p. 10)
Homeostasis is the condition in which body functions,fluids, and other
factors of the internal environment are maintained at levels suitable to
support life.
Negative Feedback
1. Negative-feedback mechanisms operate to maintain homeostasis.
2. Many negative-feedback mechanisms consist ofa receptor,control
center,and effector.
Positive Feedback
1. Positive-feedback mechanisms usually increase deviations from
normal.
2. Although a few positive-feedback mechanisms normally exist in the
body,most positive-feedback mechanisms are harmful.
Terminologyand the Body Plan
(p. 13)
BodyPositions
1. A human standing erect with the face directed forward,the arms
hanging to the side,and the palms facing forward is in the anatomic
position.
2. A person lying face upward is supine and face downward is prone.
DirectionalTerms
Directional terms always refer to the anatomic position,no matter what
the actual position ofthe body (see table 1.1).
BodyParts and Regions
1. The body can be divided into the limbs,upper and lower,and a
central region consisting ofthe head, neck, and trunk regions.
2. Superficially the abdomen can be divided into quadrants or nine
regions.These divisions are useful for locating internal organs or
describing the location ofa pain or tumor.
Planes
1. Planes ofthe body
• A midsagittal (median) plane divides the body into equal left and
right halves.A parasagittal plane produces unequal left and right
parts.
• A transverse (horizontal) plane divides the body into superior and
inferior portions.
• A frontal (coronal) plane divides the body into anterior and
posterior parts.
2. Sections ofan organ
• A longitudinal section of an organ divides it along the long axis.
• A cross (transverse) section cuts at a right angle to the long axis of
an organ.
• An oblique section cuts across the long axis of an organ at an angle
other than a right angle.
BodyCavities
1. The mediastinum subdivides the thoracic cavity.
2. The diaphragm separates the thoracic and abdominal cavities.
3. Pelvic bones surround the pelvic cavity.
SerousMembranes
1. Serous membranes line the trunk cavities.The parietal portion of a
serous membrane lines the wall ofthe cavity, and the visceral
portion is in contact with the internal organs.
• The serous membranes secrete fluid that fills the space between the
visceral and parietal membranes.The serous membranes protect
organs from friction.
• The pleural membranes surround the lungs, the pericardial
membranes surround the heart,and the peritoneal membranes
line the abdominal and pelvic cavities and surround their organs.
2. Mesenteries are parts ofthe peritoneum that hold the abdominal
organs in place and provide a passageway for blood vessels and
nerves to the organs.
3. Retroperitoneal organs are located “behind”the parietal
peritoneum.
SUMMARY
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Chapter 1 The Human Organism 23
1. Physiology
a. deals with the processes or functions ofliving things.
b. is the scientific discipline that investigates the body’s structures.
c. is concerned with organisms and does not deal with different
levels oforganization, such as cells and systems.
d. recognizes the static (as opposed to the dynamic) nature ofliving
things.
e. can be used to study the human body without considering
anatomy.
2. Given the following conceptual levels for considering the body:
1. cell
2. chemical
3. organ
4. organ system
5. organism
6. tissue
Choose the correct order for these conceptual levels,from smallest
to largest.
a. 1,2,3,6,4,5
b. 2,1,6,3,4,5
c. 3,1,6,4,5,2
d. 4,6,1,3,5,2
e. 1,6,5,3,4,2
For questions 3–8,match each organ system with its correct function.
a. regulates other organ systems
b. removes waste products from the blood;maintains water balance
c. regulates temperature;prevents water loss; provides protection
d. removes foreign substances from the blood;combats disease;
maintains tissue fluid balance
e. produces movement;maintains posture; produces body heat
3. endocrine system
4. integumentary system
5. lymphatic system
6. muscular system
7. nervous system
8. urinary system
9. The characteristic oflife that is defined as “all the chemical reactions
taking place in an organism”is
a. development.
b. growth.
c. metabolism.
d. organization.
e. responsiveness.
10. Negative-feedback mechanisms
a. make deviations from the set point smaller.
b. maintain homeostasis.
c. are associated with an increased sense ofhunger the longer a
person goes without eating.
d. all ofthe above.
11. The following events are part ofa negative-feedback mechanism.
1. Blood pressure increases.
2. Control center compares actual blood pressure to the blood
pressure set point.
3. The heart beats faster.
4. Receptors detect a decrease in blood pressure.
Choose the arrangement that lists the events in the order they occur.
a. 1,2,3,4
b. 1,3,2,4
c. 3,1,4,2
d. 4,2,3,1
e. 4,3,2,1
12. Which ofthese statements concerning positive feedback is correct?
a. Positive-feedback responses maintain homeostasis.
b. Positive-feedback responses occur continuously in healthy
individuals.
c. Birth is an example ofa normally occurring positive-feedback
mechanism.
d. When the cardiac muscle receives an inadequate supply ofblood,
positive-feedback mechanisms increase blood flow to the heart.
e. Medical therapy seeks to overcome illness by aiding positive-
feedback mechanisms.
13. The clavicle (collarbone) is to the nipple ofthe
breast.
a. anterior
b. distal
c. superficial
d. superior
e. ventral
14. A term that means nearer the attached end ofa limb is
a. distal.
b. lateral.
c. medial.
d. proximal.
e. superficial.
15. Which ofthese directional terms are paired most appropriately as
opposites?
a. superficial and deep
b. medial and proximal
c. distal and lateral
d. superior and posterior
e. anterior and inferior
16. The part ofthe upper limb between the elbow and the wrist is called
the
a. arm.
b. forearm.
c. hand.
d. inferior arm.
e. lower arm.
17. A patient with appendicitis usually has pain in the
quadrant ofthe body.
a. lower-left
b. lower-right
c. upper-left
d. upper-right
18. A plane that divides the body into anterior and posterior parts is a
a. frontal (coronal) plane.
b. sagittal plane.
c. transverse plane.
19. The pelvic cavity contains the
a. kidneys.
b. liver.
c. spleen.
d. stomach.
e. urinary bladder.
20. The lungs are
a. part ofthe mediastinum.
b. surrounded by the pericardial cavity.
c. found within the thoracic cavity.
d. separated from each other by the diaphragm.
e. surrounded by mucous membranes.
21. Given these characteristics:
1. reduce friction between organs
2. line fluid-filled cavities
3. line trunk cavities that open to the exterior ofthe body
REVIEW AND COMPREHENSION
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Part1 Organization ofthe Human Body24
Which ofthe characteristics describe serous membranes?
a. 1,2
b. 1,3
c. 2,3
d. 1,2,3
22. Given these organ and cavity combinations:
1. heart and pericardial cavity
2. lungs and pleural cavity
3. stomach and peritoneal cavity
4. kidney and peritoneal cavity
Which ofthe organs is correctly paired with a space that surrounds
that organ?
a. 1,2
b. 1,2,3
c. 1,2,4
d. 2,3,4
e. 1,2,3,4
23. Which ofthese membrane combinations are found on the surface of
the diaphragm?
a. parietal pleura—parietal peritoneum
b. parietal pleura—visceral peritoneum
c. visceral pleura—parietal peritoneum
d. visceral pleura—visceral peritoneum
24. Mesenteries
a. are found in the pleural,pericardial, and abdominopelvic cavities.
b. consist oftwo layers of peritoneum fused together.
c. anchor organs such as the kidneys and urinary bladder to the
body wall.
d. are found primarily in body cavities that open to the outside.
e. all ofthe above.
25. Which ofthe following organs is not retroperitoneal?
a. adrenal glands
b. urinary bladder
c. kidneys
d. pancreas
e. stomach
Answers in Appendix F
1. Exposure to a hot environment causes the body to sweat.The hotter
the environment,the greater the sweating. Two anatomy and
physiology students are arguing about the mechanisms involved:
Student A claims that they are positive feedback,and student B
claims they are negative feedback.Do you agree with student A or
student B and why?
2. The following observations were made on a patient who had
suffered a bullet wound:Heart rate elevated and rising. Blood
pressure very low and dropping.After bleeding was stopped and a
blood transfusion was given,blood pressure increased. Which of the
following statements is (are) consistent with these observations?
a. Negative-feedback mechanisms are occasionally inadequate
without medical intervention.
b. The transfusion interrupted a positive-feedback mechanism.
c. The transfusion interrupted a negative-feedback mechanism.
d. The transfusion was not necessary.
e. Both a and b.
3. Provide the correct directional term for the following statement:
When a boy is standing on his head,his nose is to
his mouth.
4. Complete the following statements,using the correct directional
terms for a human being.Note that more than one term can apply.
a. The navel is to the nose.
b. The nipple is to the lung.
c. The arm is to the forearm.
d. The little finger is to the index finger.
5. The esophagus is a muscular tube that connects the pharynx
(throat) to the stomach.In which quadrant and region is the
esophagus located? In which quadrant and region is the urinary
bladder located?
6. Given the following procedures:
1. Make an opening into the mediastinum.
2. Lay the patient supine.
3. Lay the patient prone.
4. Make an incision through the pericardial serous membranes.
5. Make an opening into the abdomen.
Which ofthe procedures should be accomplished to expose the
anterior surface ofa patient’s heart?
a. 2,1,4
b. 2,5,4
c. 3,1,4
d. 3,5,4
7. During pregnancy,which of the mother’s body cavities increases
most in size?
8. A bullet enters the left side ofa man, passes through the left lung,
and lodges in the heart.Name in order the serous membranes and
their cavities through which the bullet passes.
9. A woman falls while skiing and accidentally is impaled by her ski
pole.The pole passes through the abdominal body wall and into and
through the stomach,pierces the diaphragm, and finally stops in the
left lung.List in order the serous membranes the pole pierces.
Answers in Appendix G
CRITICAL THINKING
Seeley−Stephens−Tate:
Anatomy and Physiology,
Sixth Edition
I. Organization of the
Human Body
1. The Human Organism
© The McGraw−Hill
Companies, 2004
Chapter 1 The Human Organism 25
1. The chemical level is the level at which correction is currently being
accomplished.Insulin can be purchased and injected into the
circulation to replace the insulin normally produced by the
pancreas.Another approach is drugs that stimulate pancreatic cells
to produce insulin.Current research is directed at transplanting cells
that can produce insulin.Another possibility is a partial transplant
oftissue or a complete organ transplant.
2. Negative-feedback mechanisms work to control respiratory rates so
that body cells have adequate oxygen and are able to eliminate
carbon dioxide.The greater the respiratory rate, the greater the
exchange ofgases between the body and the air. When a person is at
rest,there is less of a demand for oxygen, and less carbon dioxide is
produced than during exercise.At rest,homeostasis can be
maintained with a low respiration rate.During exercise there is a
greater demand for oxygen,and more carbon dioxide must be
eliminated.Consequently, to maintain homeostasis during exercise,
the respiratory rate increases.
3. The sensation ofthirst is involved in a negative-feedback
mechanism that maintains body fluids.The sensation of thirst
increases with a decrease in body fluids.The thirst mechanism
causes a person to drink fluids,which returns body fluid levels to
normal,thereby maintaining homeostasis.
4. In the cat,cephalic and anterior are toward the head; dorsal and
superior are toward the back.In humans, cephalic and superior are
toward the head;dorsal and posterior are toward the back.
5. Your kneecap is both proximal and superior to the heel.It is also
anterior to the heel because it is on the anterior side ofthe lower
limb,whereas the heel is on the posterior side.
6. The spleen is in the left-upper quadrant,the gallbladder is in the
right-upper quadrant,the left kidney is in the left-upper quadrant,
the right kidney is in the right-upper quadrant,the stomach is
mostly in the left-upper quadrant,and the liver is mostly in the
right-upper quadrant.
7. There are two ways in which an organ can be located within the
abdominopelvic cavity but not be within the peritoneal cavity.First,
the visceral peritoneum wraps around organs.Thus the peritoneal
cavity surrounds the organ,but the organ is not inside the
peritoneal cavity.The peritoneal cavity contains only peritoneal
fluid.Second, retroperitoneal organs are in the abdominopelvic
cavity,but they are between the wall of the abdominopelvic cavity
and the parietal peritoneal membrane.
ANSWERS TO PREDICT QUESTIONS
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