Saladin anatomy and physiology unity of form and function 6th c2012 txtbk 1

To help students manage the tremendous amount of information in this introductory course, the narrative is broken into short segments, each framed by expected learning outcomes and self-

&

Kenneth S Saladin

Georgia College & State University

The Unity of Form and Function

ANATOMY & PHYSIOLOGY: THE UNITY OF FORM AND FUNCTION, SIXTH EDITION

Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY

10020 Copyright © 2012 by The McGraw-Hill Companies, Inc All rights reserved Previous editions © 2010, 2007, and 2004 No

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Library of Congress Cataloging-in-Publication Data

Saladin, Kenneth S.

Anatomy & physiology : the unity of form and function / Kenneth S Saladin 6th ed.

Includes index.

ISBN 978–0–07–337825–1 — ISBN 0–07–337825–9 (hard copy : alk paper) 1 Human physiology 2 Human anatomy I Title

II Title: Anatomy and physiology

612 dc22

2010042586

www.mhhe.com

Organization of the Body

1 Major Themes of Anatomy and Physiology 1

Atlas A General Orientation to Human

Anatomy 28

2 The Chemistry of Life 42

3 Cellular Form and Function 78

4 Genetics and Cellular Function 114

5 Histology 143

PART TWO

Support and Movement

6 The Integumentary System 180

7 Bone Tissue 206

8 The Skeletal System 233

9 Joints 278

10 The Muscular System 312

Atlas B Regional and Surface Anatomy 379

14 The Brain and Cranial Nerves 511

15 The Autonomic Nervous System and

Visceral Reflexes 561

16 Sense Organs 582

17 The Endocrine System 633

PART FOUR

Regulation and Maintenance

18 The Circulatory System: Blood 678

19 The Circulatory System: The Heart 714

20 The Circulatory System: Blood Vessels

and Circulation 749

21 The Lymphatic and Immune Systems 808

22 The Respiratory System 854

23 The Urinary System 895

24 Water, Electrolyte, and Acid–Base Balance 930

25 The Digestive System 953

26 Nutrition and Metabolism 1000

PART FIVE

Reproduction and Development

27 The Male Reproductive System 1034

28 The Female Reproductive System 1064

29 Human Development and Aging 1102

Appendix A Periodic Table A-1 Appendix B Answer Keys A-2Appendix C Symbols of Weight and Measures A-13Appendix D Biomedical Abbreviations A-14Glossary G-1

Credits C-1Index I-1

KENNETH S SALADIN has taught since 1977 at

Georgia College and State University in Milledgeville,

Georgia He earned a B.S in zoology at Michigan State

University and a Ph.D in parasitology at Florida State

University, with interests especially in the sensory

ecol-ogy of freshwater invertebrates In addition to human

anatomy and physiology, his teaching experience includes

histology, parasitology, animal behavior, sociobiology,

introductory biology, general zoology, biological

etymol-ogy, and study abroad in the Galápagos Islands Ken has

been recognized as “most significant undergraduate

men-tor” nine times over the years by outstanding students

inducted into Phi Kappa Phi He received the university’s

Excellence in Research and Publication Award for the

first edition of this book, and was named Distinguished

Professor in 2001

Author

Ken is a member of the Human Anatomy and Physiology Society, the Society for Integrative and Com-parative Biology, the American Association of Anatomists, and the American Association for the Advancement of Science He served as a developmental reviewer and wrote supplements for several other McGraw-Hill anatomy and physiology textbooks for a number of years before becom-ing a textbook writer

Ken’s outside interests include the Big Brothers/

Big Sisters program for single-parent children, the Charles Darwin Research Station in the Galápagos, and student scholarships Ken is married to Diane Saladin, a regis-tered nurse They have two adult children

This book is dedicated

to the memory of

H Kenneth Hamill and with gratitude to Big Brothers–Big Sisters of Greater Kalamazoo Big Brothers–Big Sisters of America

iv

Ken in 1964

book for McGraw-Hill in 1993, and in

1997 the first edition of The Unity of

Form and Function was published

In 2011 the story continues with the

sixth edition of Ken’s best-selling A&P

textbook

The first edition (1997)

The story continues (2011)

One of Ken’s drawings

from Hydra Ecology

Ken's “first book,” Hydra

–Ken Saladin

A Good Story

made of many layers including the core science, clinical applications, the

history of medicine, and the evolution of the human body Saladin

combines this humanistic perspective on anatomy and physiology with

vibrant photos and art to convey the beauty and excitement of the subject

to beginning students

To help students manage the

tremendous amount of information

in this introductory course, the

narrative is broken into short

segments, each framed by expected

learning outcomes and self-testing

review questions This

presentation strategy works as a

whole to create a more efficient

and effective way for students to

Engaging Chapter Layouts Tiered Assessments Based on Key Lists of Expected Learning OutcomesInnovative Chapter Sequencing xvThe Saladin Digital Story xvi-xix

What’s New in the Sixth Edition?

“Ken Saladin’s Anatomy &

Physiology: The Unity of Form

and Function, 6th edition,

pro-vides a fresh approach to the study of A&P, with modern ped- agogy, an abundance of ancil- lary learning resources, and the most up-to-date information

Instructors and students alike will benefit from the Saladin experience.”

–David Manry, Hillsborough

Community College

New Atlas Organization

Many figures of regional anatomy (former figs A.12–A.22) are moved

from atlas A to atlas B, now titled “Regional and Surface Anatomy.”

Beside shortening atlas A and moving the student more quickly to

chapter 2, this moves some anatomical detail to a later point where

students will be better equipped to understand it and relate it to

surface anatomy

New Deeper Insight Essays

New essays introduce contemporary issues in health science and a

fascinating historical account that underscores some principles of

respiratory physiology.

• Trans fats and cardiovascular disease (Deeper Insight 2.3)

• Bone marrow and cord blood transplants (Deeper Insight 18.3)

• Altitude sickness and the Zenith ballooning tragedy (Deeper Insight 22.3)

It’s not unusual to hear book cynics say that new edi- tions are just the same material bound in new covers, but that certainly isn’t true of this one

text-Just listing my sixth-edition changes came to 50 pages and 18,000 words.

—Ken Saladin

vi

Saladin’s Anatomy & Physiology, sixth edition, stays abreast

of key developments in science Yet, more efficient

writ-ing and illustration result in a book slightly shorter than

the fifth edition even with these additions.

• Advances in tissue engineering (chapter 5)

• The stem-cell controversy and induced pluripotent

stem cells (chapter 5)

• Melanoma (chapter 6)

• Cola beverages and bone loss (chapter 7)

• Bases of muscle fatigue (chapter 11)

• Microglia and astrocyte functions (chapter 12)

• Neural mechanism of working memory (chapter 12)

• Hypothalamic control of hunger and satiety

(chapter 14)

• Orexins, sleep, and narcolepsy (chapter 14)

• Vascular pathogenesis in diabetes mellitus (chapter 17)

• Glycemic index of foods (chapter 26)

• Treatment of alcoholism (chapter 26)

• Vaccination against human papillomavirus (chapter 27)

• In vitro fertilization and the 2010 Nobel Prize

(chapter 29)

New Writing

Several sections have been rewritten for improved clarity,

especially:

• Carrier-mediated membrane transport (chapter 3)

• Genetic translation and ribosomal function (chapter 4)

• A better example of an anatomical second-class lever

(chapter 9)

• Muscle compartments and blood supply (chapter 10)

• Smooth muscle physiology (chapter 11)

• A view of saltatory conduction more accurate than

most textbook presentations (chapter 12)

• The adrenal cortex (chapter 17)

• Causes of arteriosclerosis and distinctions between

arteriosclerosis and atherosclerosis (chapter 20)

New Photographs

• Male-female pelvic differences (fig 8.37)

• Treatment of infant hip dislocation (fig 9.27)

• External anatomy of the orbital region (fig 16.22)

• Use of a spirometer (fig 22.17)

• Cis- and trans-fatty acids (fig 2.20)

• Genetic translation (fig 4.8)

• Types of cell junctions (fig 5.28)

• Embryonic development of exocrine and endocrine glands (fig 5.29)

• Serous membrane histology (fig 5.33b)

• The femur as a second-class lever (fig 9.9b)

• The spinal reflex arc (fig 13.21)

• Oxyhemoglobin dissociation curves (figs 22.24 and 22.27)

• Connective Issues art and layouts

New Pedagogy

• Brushing Up is fleshed out and repositioned to better

catch the student’s attention and emphasize the importance of understanding earlier material before starting a new chapter

• A list of Expected Learning Outcomes heads up each

chapter subdivision and exercises called Assess Your Learning Outcomes end each chapter as a whole

Instructors can now easily show how their courses are outcome-driven

• Apply What You Know questions, formerly called

Think About It, stress that these thought exercises are analytical applications of basic anatomy and physiol-ogy knowledge to clinical situations and other new contexts Students can see how the basic anatomy and physiology they are learning will be relevant to ana-lyzing new problems

• Building Your Medical Vocabulary, new to each

end-of-chapter Study Guide, focuses on familiarity with the most common and useful biomedical word roots and affixes Like a mini-medical vocabulary course, this will help students with retention, spelling, and insight into medical terms, and ability to more com-fortably approach even new terms beyond the scope

of this book

• Muscle tables in chapter 10 are organized in a new,

more columnar format and enhanced with new color shading for easier reading and learning

Homeostasis and Negative Feedback

The human body has a remarkable capacity for self- restoration Hippocrates commented that it usually returns to a state of equilibrium by itself, and people recover from most illnesses even without the help of

a physician This tendency results from homeostasis18

(HO-me-oh-STAY-sis), the body’s ability to detect change, activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions.

French physiologist Claude Bernard (1813–78)

observed that the internal conditions of the body remain quite constant even when external conditions vary greatly

For example, whether it is freezing cold or swelteringly hot outdoors, the internal temperature of the body stays within a range of about 36° to 37°C (97°–99°F) Ameri can physiologist Walter Cannon (1871–1945) coined the term

homeo stasis for this tendency to maintain internal

stabil-ity Homeostasis has been one of the most enlightening theories in physiology We now see physiology as largely

a group of mechanisms for maintaining homeostasis, and the loss of homeostatic control as the cause of illness and death Pathophysiology is essentially the study of

18 homeo = the same; stas = to place, stand, stay

Z

The Temporal Bones

If you palpate your skull just above and anterior

to the ear—that is, the temporal region—you can feel the temporal bone, which forms the

lower wall and part of the floor of the cranial cavity (fig 8.10) The temporal bone derives its name from the fact that people often develop their first gray hairs on the temples with the passage of time 9 The relatively complex shape

of the temporal bone is best understood by dividing it into four parts:

e

●

Appropriate Level

• Plain language for A&P students early in their curricula

• Careful word selection and paragraph structure

• Appropriate for all audiences (international

readers, English as a second language, and

• Review activities integrated in the chapter

• Self-teaching prompts and simple experiments

liberally seeded through the narrative

• Learning aids such as pronunciation guides and

insights into the origins and root meanings of

Familiarity with word origins helps students retain meaning and spelling.

“The physiological mechanisms presented throughout the text emphasize the basic fundamental processes that occur in the human body I believe the information is simplistic enough for students to compre- hend yet detailed to provide important information […] for students and for instructors to present during lectures.”

—Scott Pallotta, Baker College at Allen Park

viii

Action potential

in progress

membrane Excitable membrane

+ + + + + + + + + – – – + + + + + +

+ + + + + + + + + – – – + + + + + + – – – – – – – – – + + + – – – – – –

+ + + + – – – + + + + + + + + + + +

+ + + + – – – + + + + + + + + + + + – – – – + + + – – – – – – – – – – –

– – – – + + + – – – – – – – – – – –

– – – – – – – – – + + + – – – – – –

+ + + + + + + + + + + + + – – – + +

+ + + + + + + + + + + + + – – – + + – – – – – – – – – – – – – + + + – –

– – – – – – – – – – – – – + + + – –

Dendrites Cell body Axon

Signal

458 PART THREE Integration and Control

voltage-gated channels immediately distal to the action potential Sodium and potassium channels open and close just as they did at the trigger zone, and a new action poten- tial is produced By repetition, this excites the membrane immediately distal to that This chain reaction continues until the traveling signal reaches the end of the axon.

Note that an action potential itself does not travel along an axon; rather, it stimulates the production of a new action potential in the membrane just ahead of it Thus,

we can distinguish an action potential from a nerve signal.

The nerve signal is a traveling wave of excitation produced

by self-propagating action potentials It is like a line of falling dominoes No one domino travels to the end of the

is a transmission of energy from the first domino to the last

Similarly, no one action potential travels to the end of an axon; a nerve signal is a chain reaction of action potentials.

If one action potential stimulates the production of a new one next to it, you might think that the signal could does not occur, however, because the membrane behind the nerve signal is still in its refractory period and cannot

stimulation The refractory period thus ensures that nerve signals are conducted in the proper direction, from the soma to the synaptic knobs.

A traveling nerve signal is an electrical current, but

it is not the same as a current traveling through a wire A current in a wire travels millions of meters per second and

is decremental—it gets weaker with distance A nerve nal is much slower (not more than 2 m/s in unmyelinated

sig-fibers), but it is nondecremental Even in the longest axons,

the last action potential generated at a synaptic knob has the same voltage as the first one generated at the trigger zone To clarify this concept, we can compare the nerve signal to a burning fuse When a fuse is lit, the heat ignites itself in a self-propagating fashion until the end of the fuse

is reached At the end, the fuse burns just as hotly as it did

at the beginning In a fuse, the combustible powder is the

a nondecremental fashion In an axon, the potential energy comes from the ion gradient across the plasma membrane

self-propagating, like the burning of a fuse.

Myelinated Fibers

Matters are somewhat different in myelinated fibers

covered internodes—fewer than 25/μm 2 in these regions compared with 2,000 to 12,000/μm 2 at the nodes of Ranvier There would be little point in having ion chan- nels in the internodes—myelin insulates the fiber from the ECF at these points, and Na + from the ECF could not flow into the cell even if more channels were present

Therefore, no action potentials can occur in the nodes, and the nerve signal requires some other way of traversing the distance from one node to the next.

When Na + enters the axon at a node of Ranvier, it diffuses for a short distance along the inner face of the axolemma (fig 12.17a) Each sodium ion has an electri- cal field around it When one Na + moves toward another, its field repels the second ion, which moves slightly and each other if you try to push their north poles together

No one ion moves very far, but this energy transfer travels down the axon much faster and farther than any distance, however, partly because the axoplasm resists the movement of the ions and partly because Na + leaks back out of the axon along the way Therefore with

Na + to relay the charge Furthermore, with a surplus of positive charges on the inner face of the axolemma and cations and  anions are attracted to each other through attracting each other through a sheet of cardboard This

FIGURE 12.16 Conduction of a Nerve Signal in an Unmyelinated Fiber Note that the membrane polarity is reversed in the region of the

action potential (red) A region of membrane in its refractory period (yellow) trails the action potential and prevents the nerve signal from going backward toward the soma The other membrane areas (green) are fully polarized and ready to respond

axon; a nerve signal is a chain reaction of action

If one action potential stimulates the produ new one next to it, you might think that the si also start traveling backward and return to the s does not occur, however, because the membra

be restimulated Only the membrane ahead is s

Foot fixed

Anterior cruciate ligament (torn) Tibial collateral ligament (torn)

Patellar ligament

Medial meniscus (torn)

Twisting motion

CHAPTER 9 Joints 305

The ligaments of the ankle include (1) anterior and posterior tibiofibular ligaments, which bind the tibia to the

fibula; (2) a multipart medial (deltoid30) ligament, which

binds the tibia to the foot on the medial side; and (3) a tipart lateral (collateral) ligament, which binds the fibula

mul-to the foot on the lateral side The calcaneal (Achilles) tendon extends from the calf muscles to the calcaneus It

plantarflexes the foot and limits dorsiflexion Plantar ion is limited by extensor tendons on the anterior side of the ankle and by the anterior part of the joint capsule.

flex-Sprains (torn ligaments and tendons) are common at the ankle, especially when the foot is suddenly inverted or everted to excess They are painful and usually accompa-

bilizing the joint and reducing swelling with an ice pack, but in extreme cases may require a cast or surgery Sprains and other joint disorders are briefly described in table 9.1.

13 Explain how the biceps tendon braces the shoulder joint.

14 Identify the three joints found at the elbow and name the movements in which each joint is involved.

15 What keeps the femur from slipping backward off the tibia?

16 What keeps the tibia from slipping sideways off the talus?

FIGURE 9.30 Knee Injuries.

DEEPER INSIGHT 9.4 Clinical Application Knee Injuries and Arthroscopic Surgery

Although the knee can bear a lot of weight, it is highly vulnerable to (as in skiing or running) and receives a blow from behind or from the cruciate ligament (ACL) (fig 9.30) Knee injuries heal slowly because ligaments and tendons have a scanty blood supply and cartilage usually has no blood vessels at all.

The diagnosis and surgical treatment of knee injuries have been

greatly improved by arthroscopy, a procedure in which the interior

inserted through a small incision The arthroscope has a light, a lens, and fiber optics that allow a viewer to see into the cavity and take photographs or video recordings A surgeon can also with- draw samples of synovial fluid by arthroscopy or inject saline into

is required, additional small incisions can be made for the cal instruments and the procedures can be observed through the less tissue damage than conventional surgery and enables patients

surgi-to recover more quickly.

Orthopedic surgeons now often replace a damaged ACL with

a graft from the patellar ligament or a hamstring tendon The geon “harvests” a strip from the middle of the patient’s ligament (or threads the ligament through the holes, and fastens it with biodegrad- able screws The grafted ligament is more taut and “competent” than

sur-as a substrate for the deposition of more collagen, which further

a patient typically must use crutches for 7 to 10 days and undergo exercise therapy Healing is completed in about 9 months.

30delt = triangular, Greek letter delta (∆); oid = resembling

voltage as the first one generated at the trigger la

b m e A n po m si a

e

e te t w h t th d th N r o th on w i h m o th h d ra e

oltage as the first one generated at the trigger a

m e A n m i a

e

e e w h t h

h N r o h i n w v e h a d a

voltage-gated channels immediately distal to the action potential Sodium and potassium channels open and close just as they did at the trigger zone, and a new action poten- tial is produced By repetition, this excites the membrane immediately distal to that This chain reaction continues until the traveling signal reaches the end of the axon.

Note that an action potential itself does not travel along an axon; rather, it stimulates the production of a new action potential in the membrane just ahead of it Thus,

we can distinguish an action potential from a nerve signal.

The nerve signal is a traveling wave of excitation produced

by self-propagating action potentials It is like a line of falling dominoes No one domino travels to the end of the line, but each domino pushes over the next one and there

is a transmission of energy from the first domino to the last

Similarly, no one action potential travels to the end of an axon; a nerve signal is a chain reaction of action potentials.

If one action potential stimulates the production of a new one next to it, you might think that the signal could also start traveling backward and return to the soma This does not occur, however, because the membrane behind the nerve signal is still in its refractory period and cannot

be restimulated Only the membrane ahead is sensitive to

ential travels to the end of an

n reaction of action potentials.

timulates the production of a

ht think that the signal could

d and return to the soma This ecause the membrane behind

s refractory period and cannot embrane ahead is sensitive to

“Saladin is a gifted author, and his tional tone will be sure to keep students very engaged.”

conversa-—Davonya Person, Auburn University

Interesting Reading

• Students say the enlightening

analogies, clinical applications, historical notes, biographical vignettes, and evolutionary insights make the book not merely informative, but a pleasure to read

• Even instructors say they often

learn something new and interesting from Saladin’s innovative perspectives

Alexis St Martin (1794–1880) William Beaumont (1785–1853)

FIGURE 25.33 Doctor and Patient in a Pioneering Study of Digestion

DEEPER INSIGHT 25.5 Medical History

The Man with a Hole in His Stomach

Perhaps the most famous episode in the history of digestive

physi-ology began with a grave accident in 1822 on Mackinac Island in

northern Michigan Alexis St Martin, a 28-year-old Canadian voyageur

(fig 25.33), was standing outside a trading post when he was

acciden-tally hit by a shotgun blast from 3 feet away A frontier Army doctor

stationed at Fort Mackinac, William Beaumont, was summoned to

examine St Martin As Beaumont later wrote, “a portion of the lung as

burnt flesh Below that was a portion of the stomach with a puncture

to pick out bone fragments and dress the wound, though he did not

expect St Martin to survive.

Surprisingly, he lived Over a period of months the wound

extruded pieces of bone, cartilage, gunshot, and gun wadding As

that Beaumont had to cover it with a compress to prevent food from

coming out The opening remained, covered only by a loose flap of

skin, for the rest of St Martin's life A fold of tissue later grew over the

Town authorities decided they could no longer support him on public

funds and wanted to ship him 1,500 miles to his home Beaumont,

was known about digestion, and he saw the accident as a unique

opportunity to learn He took St Martin in at his personal expense and

never attended medical school and had little idea how scientists work,

yet he proved to be an astute experimenter Under crude frontier

conditions and with almost no equipment, he discovered many of the

basic facts of gastric physiology discussed in this chapter.

“I can look directly into the cavity of the stomach, observe its

motion, and almost see the process of digestion,” Beaumont wrote

“I can pour in water with a funnel and put in food with a spoon, and

into the stomach and removed them hourly for examination He sent

vials of gastric juice to the leading chemists of America and Europe,

who could do little but report that it contained hydrochloric acid He

stomach, but he found that HCl alone did not digest meat; gastric

juice must contain some other digestive ingredient Theodor Schwann,

one of the founders of the cell theory, identified that ingredient as

only in response to food; it did not accumulate between meals as

the walls of the empty stomach rubbing against each other.

Now disabled from wilderness travel, St Martin agreed to

participate in Beaumont's experiments in exchange for room and

board—though he felt helpless and humiliated by it all The fur

trap-pers taunted him as “the man with a hole in his stomach,” and he

longed to return to his work in the wilderness He had a wife and

repeatedly to join them He was once gone for 4 years before erty made him yield to Beaumont’s financial enticement to come

pov-and was quite insensitive to his embarrassment pov-and discomfort over

the first direct observations of the relationship between emotion and digestion When St Martin was particularly distressed, Beaumont

nervous system inhibits digestive activity.

Beaumont published a book in 1833 that laid the foundation for modern gastric physiology and dietetics It was enthusiastically

physiologist Ivan Pavlov (1849–1936) performed his celebrated ments on digestion in animals Building on the methods pioneered by Beaumont, Pavlov received the 1904 Nobel Prize for Physiology or Medicine.

experi-In 1853, Beaumont slipped on some ice, suffered a blow to the base of his skull, and died a few weeks later St Martin continued

to tour medical schools and submit to experiments by other ologists, whose conclusions were often less correct than Beaumont’s

physi-Some, for example, attributed chemical digestion to lactic acid instead of hydrochloric acid St Martin lived in wretched poverty in a

Beaumont By then he was senile and believed he had been to Paris, where Beaumont had often promised to take him.

1076 PART FIVE Reproduction and Development

stimulates gonadotropin secretion Therefore, if body fat and leptin levels drop too low, gonadotropin secretion cease Adolescent girls with very low body fat, such as

a later age than average.

Menarche does not necessarily signify fertility A

girl’s first few menstrual cycles are typically anovulatory

about a year after they begin menstruating

Estradiol stimulates many other changes of puberty It causes the vaginal metaplasia described earlier It stimu- lates growth of the ovaries and secondary sex organs It increase in height and widening of the pelvis Estradiol is stimulates fat deposition in the mons pubis, labia majora, hips, thighs, buttocks, and breasts It makes a girl’s skin than in males of corresponding age.

Progesterone27 acts primarily on the uterus, ing it for possible pregnancy in the second half of each menstrual cycle and playing roles in pregnancy discussed later Estrogens and progesterone also suppress FSH and anterior pituitary Inhibin selectively suppresses FSH

prepar-secretion.

Thus, we see many hormonal similarities in males and females from puberty onward The sexes differ less their relative amounts—high levels of androgens and females Another difference is that these hormones are secreted more or less continually and simultaneously cyclic and the hormones are secreted in sequence This menstrual cycles.

Climacteric and Menopause

Women, like men, go through a midlife change in mone secretion called the climacteric In women, it is

hor-accompanied by menopause, the cessation of

menstrua-tion (see Deeper Insight 28.2).

A female is born with about 2 million eggs in her ries, each in its own follicle The older she gets, the fewer but when she has only about 1,000 follicles left Even the they secrete less estrogen and progesterone Without these steroids, the uterus, vagina, and breasts atrophy Intercourse may become uncomfortable, and vaginal infections more

ova-common, as the vagina becomes thinner, less distensible, and drier The skin becomes thinner, cholesterol levels bone mass declines (increasing the risk of osteoporosis)

hormone balances, and the sudden dilation of ous arteries may cause hot flashes—a spreading sense of

cutane-heat from the abdomen to the thorax, neck, and face Hot flashes may occur several times a day, sometimes accompa- nied by headaches resulting from the sudden vasodilation

of arteries in the head In some people, the changing monal profile also causes mood changes Many physicians

hor-of estrogen and progesterone usually taken orally or by a and benefits of HRT are still being debated.

Apply What You Know

FSH and LH secretion rise at climacteric and these mones attain high concentrations in the blood Explain this the pituitary–gonadal relationship.

hor-Menopause is the cessation of menstrual cycles, ally occurring between the ages of 45 and 55 The average about 52 It is difficult to precisely establish the time of menopause because the menstrual periods can stop for several months and then begin again Menopause is gen- erally considered to have occurred when there has been

usu-no menstruation for a year or more.

27 pro = favoring; gest = pregnancy; sterone = steroid hormone

DEEPER INSIGHT 28.2 Evolutionary Medicine The Evolution of Menopause

There has been considerable speculation about why women do not remain fertile to the end of their lives, as men do Some theorists argue that menopause served a biological purpose for our prehistoric foremothers Human offspring take a long time to rear Beyond a cer- tain point, the frailties of age make it unlikely that a woman could rear might do better in the long run to become infertile and finish rearing her last child, or help to rear her grandchildren, instead of having more In this view, menopause was biologically advantageous for our ancestors—in other words, an evolutionary adaptation.

Others argue against this hypothesis on the grounds that Pleistocene (Ice Age) skeletons indicate that early hominids rarely lived past age

40 If this is true, menopause setting in at 45 to 55  years of age may indeed have been fertile to the end of their lives; menopause have made it possible for us to live much longer than our ances- tors did.

Estradiol stimulates many other changes of puberty It causes the vaginal metaplasia described earlier It stimu- lates growth of the ovaries and secondary sex organs It increase in height and widening of the pelvis Estradiol is stimulates fat deposition in the mons pubis, labia majora, hips, thighs, buttocks, and breasts It makes a girl’s skin than in males of corresponding age.

Progesterone27 acts primarily on the uterus, ing it for possible pregnancy in the second half of each later Estrogens and progesterone also suppress FSH and anterior pituitary Inhibin selectively suppresses FSH

prepar-secretion.

Thus, we see many hormonal similarities in males and females from puberty onward The sexes differ less their relative amounts—high levels of androgens and females Another difference is that these hormones are

in males, whereas in females, secretion is distinctly will be very apparent as you read about the ovarian and menstrual cycles.

Climacteric and Menopause

Women, like men, go through a midlife change in mone secretion called the climacteric In women, it is

hor-accompanied bymenopause, the cessation of

menstrua-tion (see Deeper Insight 28.2).

A female is born with about 2 million eggs in her ries, each in its own follicle The older she gets, the fewer but when she has only about 1,000 follicles left Even the they secrete less estrogen and progesterone Without these may become uncomfortable, and vaginal infections more

ova-27pro = favoring; gest = pregnancy; sterone = steroid hormone

DEEPER INSIGHT 28.2 Evolutionary Medicine

The Evolution of Menopause

There has been considerable speculation about why women do not remain fertile to the end of their lives, as men do Some theorists argue that menopause served a biological purpose for our prehistoric foremothers Human offspring take a long time to rear Beyond a cer- tain point, the frailties of age make it unlikely that a woman could rear another infant to maturity or even survive the stress of pregnancy She might do better in the long run to become infertile and finish rearing her last child, or help to rear her grandchildren, instead of having more In this view, menopause was biologically advantageous for our ancestors—in other words, an evolutionary adaptation.

(Ice Age) skeletons indicate that early hominids rarely lived past age

40 If this is true, menopause setting in at 45 to 55  years of age could have served little purpose In this view, Pleistocene women may indeed have been fertile to the end of their lives; menopause now may be just an artifact of modern nutrition and medicine, which have made it possible for us to live much longer than our ances- tors did.

Alexis St Martin (1794–1880) umont (1785–1853)

5 5.33 33 3 Doctor and Patient in a Pioneering Study of

em inhibits digestive activity.

nt published a book in 1833 that laid the foundation gastric physiology and dietetics It was enthusiastically

van Pavlov (1849–1936) performed his celebrated gestion in animals Building on the methods pioneered by Pavlov received the 1904 Nobel Prize for Physiology or

experi-Beaumont slipped on some ice, suffer ff ed a blow to the skull, and died a few weeks later St Martin continued ical schools and submit to experiments by other physi- ose conclusions were often less correct than Beaumont’s

example, attributed chemical digestion to lactic acid drochloric acid St Martin lived in wretched poverty in a

th his wife and several children, and died 28 years after

y then he was senile and believed he had been to Paris, mont had often promised to take him.

Alexis St Martin (1794–1880) William Beaumont (1785–1853)

FIGURE 25.33 Doctor and Patient in a Pioneering Study of Digestion

who could do little but report that it contained hydrochloric acid He proved that digestion required HCl and could even occur outside the stomach, but he found that HCl alone did not digest meat; gastric juice must contain some other digestive ingredient Theodor Schwann, one of the founders of the cell theory, identified that ingredient as pepsin Beaumont also demonstrated that gastric juice is secreted

previously thought He disproved the idea that hunger is caused by the walls of the empty stomach rubbing against each other.

Now disabled from wilderness travel, St Martin agreed to participate in Beaumont's experiments in exchange for room and board—though he felt helpless and humiliated by it all The fur trap- pers taunted him as “the man with a hole in his stomach,” and he

Evolutionary Medicine Rapidly growing,

increasingly fascinating

Evolutionary medicine provides

novel and intriguing ways of

• theories of aging and death

people behind the science Students say these stories make learning A&P more fun and stimulating

More than a few distinguished scientists and cians say they found their inspiration in reading of the lives of their predecessors Maybe these stories will inspire some of our own students to go on to

clini-do great things.

–Ken Saladin

x

Microfilaments

Secretory vesicle in Desmosome

Intermediate filaments

Centrosome Microtubule undergoing disassembly

(a)

15 μm

(b)

Basement membrane

Hemidesmosome

Kinesin CHAPTER 3 Cellular Form and Function 103

FIGURE 3.25 The Cytoskeleton (a) Components of the cytoskeleton

Few organelles are shown in order to emphasize the cytoskeleton Note that all microtubules radiate from the centrosome; they often serve as trackways for motor proteins (kinesin) transporting organelles (b) Cells with their cytoskeletons labeled with fluorescent antibodies, photographed through a fluorescence microscope.

The density of a typical cytoskeleton far exceeds even that shown in part (a).

The C

re show ate fro transp antibod yp typical

r i a t Cilia

Cilia

Microvilli

Central microtubule Peripheral microtubules

Axoneme

Plasma membrane

Shaft of cilium

Dynein arms Central microtubules Axoneme:

(a)

(b)

ocardial Vortex (a) Anterior view of

um rendered transparent to expose muscle (b) View from the apex to oils around the heart This results in a ventricles contract.

ocardiall V

um rend de muscle ( oils arouu ventriclees

o

u m o v

Sets the Standard

• Stunning portfolio of art and photos

• Hundreds of accuracy reviews

• Art focus groups

Vivid Illustrations Rich textures and shading, and bold, bright colors bring structures to life.

The visual appeal of nature is immensely important

in motivating one to study it We certainly see this

at work in human anatomy—in the countless dents who describe themselves as ‘visual learners’;

stu-in the many laypeople who fstu-ind anatomy atlases so intriguing; and in the enormous popularity of Body Worlds and similar exhibitions of human anatomy.

Sternum Ribs

Left lung

Pleural cavity

Vertebra Spinal cord

Posterior

Anterior

Fat of breast Pectoralis

Aorta

Right lung Esophagus

Epidermis

Dermis Hair matrix

Sebaceous gland Old club hair

Piloerector New hair Bulge

Club hair (detached from matrix)

Club

Dermal papilla

Degeneration

of lower follicle Hair bulb

1 Anagen (early)

(Growing phase, 6–8 years)

Stem cells multiply and follicle grows deeper into dermis; hair matrix

cells multiply and keratinize, causing hair to grow upward; old club hair

may persist temporarily alongside newly growing hair.

Anagen (mature) Catagen

(Degenerative phase, 2–3 weeks) Hair growth ceases; hair bulb keratinizes and forms club hair;

lower follicle degenerates.

Telogen

(Resting phase, 1–3 months)

to level of bulge; club hair falls out, usually in telogen or next anagen.

2

1

7

8 9

Inferior vena cava

Right AV (tricuspid) valve Right ventricle

Right atrium

Superior vena cava

Pulmonary trunk

Left pulmonary artery

Left pulmonary veins

Aortic valve Left AV (bicuspid) valve Left atrium

Left ventricle 6

Blood in right atrium flows through right

AV valve into right ventricle.

Contraction of right ventricle forces pulmonary valve open.

Blood flows through pulmonary valve into pulmonary trunk.

Blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO 2 and loads O 2 Blood returns from lungs via pulmonary veins to left atrium.

Blood in left atrium flows through left AV valve into left ventricle.

Contraction of left ventricle (simultaneous with step 3) ) forces aortic valve open.

Blood flows through aortic valve into ascending aorta.

Blood in aorta is distributed to every organ in the body, where it unloads O 2 and loads CO 2 Blood returns to heart via venae cavae.

3

Sternum Ribs Fat of breast

TABLE 10.1 Muscles of Facial Expression (continued)

Depressor Anguli Oris25 Draws angle of mouth laterally and downward in opening

mouth or sad expressions

O: Inferior margin of mandibular body I: Modiolus

Facial nerve

Depressor Labii Inferioris26 Draws lower lip downward and laterally in chewing and

expressions of melancholy or doubt

O: Mandible near mental protuberance I: Skin and mucosa of lower lip

Facial nerve

The Mental and Buccal Regions Adjacent to the oral orifice are the mental region (chin) and buccal region (cheek) In addition to muscles already discussed that

act directly on the lower lip, the mental region has a pair of small mentalis muscles extending from the upper margin of the mandible to the skin of the chin In some people, these muscles are especially thick and have a visible dimple between them called the mental cleft (see fig 4.18, p 135 ) The buccinator is the muscle in the

cheek It has multiple functions in chewing, sucking, and blowing If the cheek is inflated with air, compression of the buccinator blows it out Sucking is achieved

by contracting the buccinators to draw the cheeks inward, and then relaxing them This action is especially important to nursing infants To feel this action, hold your fingertips lightly on your cheeks as you make a kissing noise You will notice the relaxation of the buccinators at the moment air is sharply drawn in through

the pursed lips The platysma is a thin superficial muscle of the upper chest and lower face It is relatively unimportant, but when men shave they tend to tense the

platysma to make the concavity between the jaw and neck shallower and the skin tauter.

O: Alveolar processes on lateral surfaces of

mandible and maxilla

I: Orbicularis oris; submucosa of cheek

O: Fascia of deltoid and pectoralis major I: Mandible; skin and subcutaneous

tissue of lower face

Facial nerve

Conducive to Learning

• Easy-to-understand process figures

• Tools for students to easily orient themselves

Orientation Tools Saladin art integrates tools

to help students quickly orient themselves within a

figure and make connections between ideas

Process Figures Saladin breaks complicated physiological processes into numbered steps for a man- ageable introduction to difficult concepts.

Muscles tables are organized in new columnar format and enhanced with new shading for easier reading and learning

pho-—Charmaine Irvin, Baker College of Allen Park

xii

• Unmyelinated Nerve Fibers 450

• Conduction Speed of Nerve Fibers 450

• Regeneration of Nerve Fibers 450

12.4 Electrophysiology of Neurons 451

• Electrical Potentials and Currents 452

• Local Potentials 454

• Action Potentials 455

• The Refractory Period 457

• Signal Conduction in Nerve Fibers 457

12.5 Synapses 460

• The Discovery of Neurotransmitters 460

• Structure of a Chemical Synapse 461

• Neurotransmitters and Related Messengers 461

• Neural Pools and Circuits 469

• Memory and Synaptic Plasticity 471

Connective Issues 474 Study Guide 475

12.3 Medical History: Nerve Growth Factor—

From Home Laboratory to Nobel Prize 452

12.4 Clinical Application: Alzheimer and

Engaging Chapter Layouts

• Chapters are structured around the way students learn

• Frequent subheadings and expected learning outcomes help students plan their study time and review strategies

Chapter Outline provides

a quick overview of the content

Deeper Insights highlight areas

of interest for students.

PEDAGOGICAL

20.1 General Anatomy of the Blood Vessels

Expected Learning Outcomes

When you have completed this section, you should be able to

a describe the structure of a blood vessel;

b describe the different types of arteries, capillaries, and veins;

c trace the general route usually taken by the blood from the heart and back again; and

d describe some variations on this route.

There are three principal categories of blood vessels:

arteries, veins, and capillaries (fig 20.1) Arteries are the

efferent vessels of the cardiovascular system—that is,

vessels that carry blood away from the heart Veins are

the afferent vessels that carry blood back to the heart

Capillaries are microscopic, thin-walled vessels that

con-nect the smallest arteries to the smallest veins Aside from their general location and direction of blood flow, these three categories of vessels also differ in the histological structure of their walls.

The Vessel Wall

The walls of arteries and veins are composed of three

layers called tunics (fig 20.2):

1 The tunica interna (tunica intima) lines the inside of

the vessel and is exposed to the blood It consists of a

simple squamous epithelium called the endo thelium

overlying a basement membrane and a sparse layer

of loose connective tissue; it is continuous with the endocardium of the heart The endothelium acts as

a selectively permeable barrier to materials entering

or leaving the bloodstream; it secretes chemicals that

normally repels blood cells and platelets so that they

the endothelium is damaged, however, platelets may adhere to it and form a blood clot; and when the tissue around a vessel is inflamed, the endothelial

Brushing Up

• The concepts of homeostatic set point and dynamic equilibrium should be reviewed (p 17) as background for understanding the control of blood pressure

• The principles of blood volume, pressure, and flow discussed in this chapter hinge on the reasons behind the osmolarity and viscosity of blood introduced on page 682

• Familiarity with cardiac systole and diastole (p 728) is necessary for understanding blood pressure in this chapter

• Blood flow is regulated by variations in cardiac output and blood vessel diameter, which are governed in part by the autonomic nervous system as discussed on page 576

• The exchange of materials between the blood capillaries and surrounding tissues is based on the principles of filtration, osmosis and osmotic pressure, diffusion, and transcytosis introduced earlier (pp. 91–100)

The route taken by the blood after it leaves the heart was a point of much confusion for many centuries In traditional Chinese medicine as early as 2650 BCE , blood was believed

to flow in a complete circuit around the body and back to the heart, just as we know today But in the second century CE , Roman physician Claudius Galen (129–c 199) argued that it flowed back and forth in the veins, like air in the bronchial tubes He believed that the liver received food directly from the esophagus and converted it to blood, the heart pumped the blood through the veins to all other organs, and those organs consumed it

The arteries were thought to contain only a mysterious vapor or

“vital spirit.”

The Chinese view was right, but the first experi mental demonstration of this did not come for another 4,000 years English physician William Harvey (1578–1657) (see p 5 ) studied the filling and emptying of the heart in snakes, tied off the vessels above and below the heart to observe the effects on cardiac filling and output, measured cardiac output in a variety of living animals, and estimated cardiac output in humans He concluded that (1) entire body, (2) not enough food is consumed to account for the continual production of so much blood, and therefore (3) the blood returns to the heart rather than being consumed by the peripheral organs He could not explain how, since the microscope had yet to

be devel oped to the point that enabled Antony van Leeuwen hoek (1632–1723) and Marcello Malpighi (1628–94) to discover the blood capillaries.

Harvey’s work was the first experimental study of animal physiology and a landmark in the history of biology and medicine

But so entrenched were the ideas of Aristotle and Galen in the medical community, and so strange was the idea of doing experiments on living animals, that Harvey’s contemporaries rejected his ideas Indeed, some of them regarded him as a

if the blood was continually recirculated and not consumed by the know, of course, that he was right Harvey’s case is one of the most interesting in biomedical history, for it shows how empirical science overthrows old theories and spawns better ones, and how common sense and blind allegiance to authority can interfere with the acceptance of truth But most importantly, Harvey’s contributions represent the birth of experimental physiology.

and be output and est

he hea entire b continu eturns organs

be dev 1632–

capillar Ha physiol But so experim ejecte

a o a th e re o 1

p t e re

Pubic symphysis

Intervertebral disc (fibrocartilage)

282 PART TWO Support and Movement

fibers that extend from the bone matrix of the jaw into

the dental tissue (see fig 9.2b) The periodontal ligament

chewing This allows us to sense how hard we are biting or

to sense a particle of food stuck between the teeth.

Syndesmoses

A syndesmosis6 (SIN-dez-MO-sis) is a fibrous joint at

which two bones are bound by relatively long collagenous

fibers The separation between the bones and length of

or gomphosis has An especially movable syndesmosis

are joined by a broad fibrous interosseous membrane This

the forearm A less movable syndesmosis is the one that

by side (see fig 9.2c).

Cartilaginous Joints

A cartilaginous joint is also called an amphiarthrosis7

(AM-fee-ar-THRO-sis) or amphiarthrodial joint In these

joints, two bones are linked by cartilage (fig 9.4) The

two types of cartilaginous joints are synchondroses and

symphyses.

Synchondroses

A synchondrosis8 (SIN-con-DRO-sis) is a joint in which the bones are bound by hyaline cartilage An example is

7amphi = on all sides; arthr = joined; osis = condition

8syn = together; chondr = cartilage; osis = condition

FIGURE 9.4 Cartilaginous Joints

(a) A synchondrosis, represented by the

costal cartilage joining rib 1 to the sternum

(b) The pubic symphysis (c) Intervertebral

discs, which join adjacent vertebrae to each

other by symphyses.

● What is the difference between the pubic

symphysis and the interpubic disc?

6syn = together; desm = band; osis = condition

B d

(c)

Interpubic disc (fibrocartilage)

rim Dislocations of the hip are rare, but some infants suffer congenital dislocations because the acetabulum is not deep enough to hold the head of the femur in place If detected early, this condition can be treated with a harness, worn for 2 to 4 months, that holds the head of the femur in the proper position until the joint is stronger (fig 9.27).

Apply What You Know

Where else in the body is there a structure similar to the acetabular labrum? What do those two locations have in common?

Ligaments that support the coxal joint include the

iliofemoral (ILL-ee-oh-FEM-oh-rul) and pubofemoral

(PYU-bo-FEM-or-ul) ligament s on the anterior side and

the i schiofemoral (ISS-kee-oh-FEM-or-ul) ligament on the

posterior side The name of each ligament refers to  the bones to which it attaches—the femur and the ilium, pubis, or ischium When you stand up, these ligaments become twisted and pull the head of the femur tightly into the acetabulum The head of the femur has a conspic-

uous pit called the fovea capiti s The round ligament, or ligamentum teres27 (TERR-eez), arises here and attaches

Tiered Assessments Based on Key

Learning Outcomes

• Chapters are divided into easily manageable

chunks, which help students

budget study time effectively

• Section-ending questions allow students to

check their understanding before moving on

End-of-chapter questions

build on all levels of Bloom's taxonomy in sections that:

1 assess learning outcomes

2 test simple recall and analytical thought

3 build medical vocabulary

4 apply the basic knowledge to new clinical problems and other situations

Questions in figure legends and

Apply What You Know items

prompt students to think more

deeply about the implications and

applications of what they have

learned

New! Each chapter begins with Brushing

Up to emphasize the interrelatedness of

con-cepts and also provides an aid to returning,

nontraditional students

Each numbered section begins with Expected

Learning Outcomes to help focus the reader’s

attention on the larger concepts and make the

course outcome-driven

xiv

Innovative Chapter

Order

Some chapters and topics are presented

in a sequence that is more instructive

than the conventional order

Early Presentation of Heredity

Fundamental principles of heredity are

presented in the last few pages of

chapter 4 rather than at the back of the

book to better integrate molecular and

mendelian genetics This organization

also prepares students to learn about

such genetic traits and conditions as

cystic fibrosis, color blindness, blood

types, hemophilia, cancer genes, or

sickle-cell disease by first teaching

them about dominant and recessive

alleles, genotype and phenotype, and

sex linkage

Muscle Anatomy and

Physiology Follow Skeleton

and Joints

The functional morphology of the

skeleton, joints, and muscles is treated

in three consecutive chapters, 8 through

10, so when students learn muscle

origins and insertions, these come only

two chapters after the names of the

relevant bone features When they learn

muscle actions, it is in the first chapter

after learning the terms for the joint

movements This order brings another

advantage: the physiology of muscle and

nerve cells is treated in two consecutive

chapters (11 and 12), which are thus

closely integrated in their treatment of

synapses, neurotransmitters, and

membrane electrophysiology

BRIEF Contents

About the Author iv Preface v Reviewers xxi Contents xxii Letter to the Students xxvi

PART ONE

Organization of the Body

1 Major Themes of Anatomy and Physiology 1 Atlas A General Orientation to Human

Anatomy 28

2 The Chemistry of Life 42

3 Cellular Form and Function 78

4 Genetics and Cellular Function 114

5 Histology 143

PART TWO

Support and Movement

6 The Integumentary System 180

14 The Brain and Cranial Nerves 511

15 The Autonomic Nervous System and

Visceral Reflexes 561

16 Sense Organs 582

17 The Endocrine System 633

PART FOUR

Regulation and Maintenance

18 The Circulatory System: Blood 678

19 The Circulatory System: The Heart 714

20 The Circulatory System: Blood Vessels

and Circulation 749

21 The Lymphatic and Immune Systems 808

22 The Respiratory System 854

23 The Urinary System 895

24 Water, Electrolyte, and Acid–Base Balance 930

25 The Digestive System 953

26 Nutrition and Metabolism 1000

PART FIVE

Reproduction and Development

27 The Male Reproductive System 1034

28 The Female Reproductive System 1064

29 Human Development and Aging 1102

Appendix A Periodic Table A-1 Appendix B Answer Keys A-3 Appendix C Symbols of Weight and Measures A-15 Appendix D Biomedical Abbreviations A-17 Glossary G-1

Credits C-1 Index I-1

Urinary System Presented Close to Circulatory and Respiratory Systems

Most textbooks place this system near the end of the book because

of its anatomical and developmental relationships with the reproductive system However, its physiological ties to the circulatory and respiratory systems are much more important

Except for a necessary digression on lymphatics and immunity, the circulatory system is followed almost immediately with the

respiratory and urinary systems

INNOVATIVE

The Saladin Digital Story

The Complete Package

Digital images (stepped-out

images, split images,

tables, photos)

Digital Resources:

Assignable Anatomy &

Physiology Revealed quizzes

MediaPhys

(physiology tutorials) Laboratory manuals

Print Resources:

Clinical applications manual

Student study guide

Instructor Resources

Course Content

Student Resources

L

d S

xvi

McGraw-Hill ConnectPlus Anatomy & Physiology is a

web-based assignment and assessment platform that gives

students the means to better connect with their

course-work, with their instructors, and with the important

concepts that they will need to know for success now

and in the future With Connect Anatomy & Physiology,

instructors can deliver assignments, quizzes and tests

easily online Students can practice important skills at

their own pace and on their own schedule With Connect

Anatomy & Physiology Plus, students also get 24/7 online

access to an eBook—an online edition of the text—to aid

them in successfully completing their work, wherever

and whenever they choose www.mhhe.com/saladin6

teaching easier and learning smarter

Engaging

Presentation Materials

for Lecture and Lab

LearnSmart is an online diagnostic learning system that

determines the level of student knowledge, and feed the student suitable content for the Anatomy & Physiology course Students learn faster and study more effectively

As a student works within the system, LearnSmart develops a personal learning path adapted to what the student has learned and retained LearnSmart is able to recommend additional study resources to help the stu-dent master topics This innovative and outstanding study tool also has features for instructors where they can see exactly what students have accomplished, and a built in assessment tool for graded assignments You can access LearnSmart through ConnectPlus

Not only do you get single sign-on with Connect™ and Create™, you also get deep integration of McGraw-Hill content and content engines right in Blackboard

Whether you’re choosing a book for your course or building Connect™ assignments, all the tools you need are right where you want them – inside of Blackboard

Gradebooks are now seamless When a student pletes an integrated Connect™ assignment, the grade for that assignment automatically (and instantly) feeds your Blackboard grade center

com-McGraw-Hill and Blackboard can now offer you easy access to industry leading technology and content, whether your campus hosts it, or we do Be sure to ask your local McGraw-Hill representative for details

McGraw-Hill Higher Education and Blackboard have

teamed up

Blackboard, the Web-based course-management system,

has partnered with McGraw-Hill to better allow

stu-dents and faculty to use online materials and activities

to complement face-to-face teaching Blackboard features

exciting social learning and teaching tools that foster

more logical, visually impactful and active learning

opportunities for students You’ll transform your

closed-door classrooms into communities where students

remain connected to their educational experience

24 hours a day

This partnership allows you and your students access to

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Measure Your Students Progress

xviii

NEW! Saladin’s Anatomy & Physiology 6th edition eBook and APR 3.0—Now, Seamlessly Integrated

New to this edition, the text, images, and artwork in the Saladin’s Anatomy & Physiology 6th edition are brought to life with the click of a mouse Wherever students see the APR 3.0 logo in their eBook, they can simply click the logo and they will be taken specifically to the dissection photos, animations, histology slides, and radiological images in APR that support and enrich their understanding of the text

If you’d like to use APR in your course, but don’t have the time to create

APR navigational directions for your students

If you’d like to use APR as a complement to your course, but don’t have the time to go through

APR and choose the views that complement the text

We understand, and we’ve done the work for you!

APR 3.0 and Saladin’s Anatomy & Physiology 6th edition are now combined into one easy-to-use, harmonious, unified system.

Anatomy & Physiology Revealed is the ultimate online

interactive cadaver dissection experience Now fully

customizable to fi t any course or lab, this state-of-the-art

program uses cadaver photos combined with a layering

technique that allows the student to peel away layers of

the human body to reveal structures beneath the surface

Anatomy & Physiology Revealed also offers animations,

histologic and radiologic imaging, audio pronunciations,

and comprehensive quizzing It can be used as part of any

one or two semester undergraduate Anatomy & Physiology

or Human Anatomy course; Anatomy & Physiology

Revealed is available stand-alone, or can be combined with

any McGraw-Hill product

Other resources available:

Student Study Guide

This comprehensive study guide written by experienced

instructor Jacque Homan in collaboration with Ken

Saladin contains vocabulary-building and

content-testing exercises, labeling exercises, and practice exams

Physiology Tutorials

MediaPhys offers detailed explanations, high-quality

illustrations, and animations to provide students with a

thorough introduction to the world of physiology—

giving them a virtual tour of physiological processes

Physiology Interactive Lab Simulations

Ph.I.L.S offers 37 lab simulations that may be used to supplement or

substitute for wet labs

Clinical Applications Manual

This manual expands on Anatomy & Physiology's

clinical themes, introduces new clinical topics, and

provides test questions and case studies to develop

students' abilities to apply knowledge to realistic

situations A print version is available for students

Lab Manual Options to Fit Your Course

The Anatomy & Physiology

Laboratory Manual by Eric Wise of

Santa Barbara City College is expressly written to coincide with

chapters of Saladin's Anatomy &

Physiology.

New! The Laboratory Manual for Human Anatomy &

Physiology by Terry Martin of Kishwaukee College is

written to coincide with Saladin or any A&P textbook

• Three versions available including main, cat, and fetal pig

• Includes Ph.I.L.S 3.0 CD-ROM

• Outcomes and assessments format

• Clear, concise writing style

Student Supplements

McGraw-Hill offers various tools and technology products

to support the textbook Students can order supplemental study materials by contacting their campus bookstore or online at www.shopmcgraw-hill.com

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Instructors can obtain teaching aides by calling the Hill Customer Service Department at 1-800-338-3987, visiting our online catalog at www.mhhe.com, or by contacting their local McGraw-Hill sales representative

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Pm

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students can save as much as 50% on selected titles

delivered on the most advanced eBook platform available

Contact your McGraw-Hill sales representative to

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Create™

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xx

Tami Asplin, North Dakota State

University

Seher Atamturktur, Bronx Community

College of CUNY

Vincent Austin, Bluegrass Community

and Technical College

Melissa M Bailey, Emporia State

Matthew Geddis, Borough of Manhattan

Community College-City Univ of NY

Elmer Godeny, Baton Rouge Community

Jo Anne Lucas, Wayne County

Community College District

Paul Luyster, Tarrant County College

Applied Arts & Sciences, Kelsey Campus

Scott Pallotta, Baker College at Allen

Ronald Slavin, Borough of Manhattan

Community College-City Univ of NY

Ken Smith, Arapahoe Community

Dr Timothy A Ballard, University of

North Carolina Wilmington

Dr Jane L Johnson-Murray, Houston

Community College

Vladimir Jurukovski, PhD, Suffolk

County Community College

Dale Smoak, Piedmont Technical College

Dr Wanda Hargroder, Louisiana State

James Horwitz, Palm Beach Community

College – Lake Worth

Sonya Williams, Oklahoma City

Community College

Teresa Gillian, Virginia Tech

Reviewers

1.7 The Language of Medicine 20

1.8 Review of Major Themes 22

Study Guide 25

Atlas A

General Orientation to Human

Anatomy 28

A.1 General Anatomical Terminology 29

A.2 Major Body Regions 31

A.3 Body Cavities and Membranes 34

A.4 Organ Systems 37

Study Guide 40

Chapter 2

The Chemistry of Life 42

2.1 Atoms, Ions, and Molecules 432.2 Water and Mixtures 502.3 Energy and Chemical Reactions 562.4 Organic Compounds 59

Study Guide 75

Chapter 3

Cellular Form and Function 7 8

3.1 Concepts of Cellular Structure 793.2 The Cell Surface 82

3.3 Membrane Transport 913.4 The Cell Interior 101

Study Guide 111

Chapter 4

Genetics and Cellular Function 114

4.1 DNA and RNA—The Nucleic Acids 115

4.2 Genes and Their Action 1204.3 DNA Replication and the Cell Cycle 129

4.4 Chromosomes and Heredity 134

Excitable Tissues 1625.5 Cell Junctions, Glands, and Membranes 164

5.6 Tissue Growth, Development, Repair, and Degeneration 171

Study Guide 177

PART TWO

Support and Movement

Chapter 6

The Integumentary System 180

6.1 The Skin and Subcutaneous Tissue 181

6.2 Hair and Nails 1906.3 Cutaneous Glands 1956.4 Skin Disorders 197

Connective Issues 202 Study Guide 203

Chapter 8

The Skeletal System 233

8.1 Overview of the Skeleton 2348.2 The Skull 236

xxii

8.4 The Pectoral Girdle and Upper

Limb 2598.5 The Pelvic Girdle and Lower

The Muscular System 312

10.1 The Structural and Functional

Organization of Muscles 31310.2 Muscles of the Head and Neck

32210.3 Muscles of the Trunk 333

10.4 Muscles Acting on the Shoulder and

Upper Limb 34310.5 Muscles Acting on the Hip and

11.5 Behavior of Whole Muscles 41811.6 Muscle Metabolism 42311.7 Cardiac and Smooth Muscle 428

Connective Issues 435 Study Guide 436

PART THREE

Integration and Control

Chapter 12Nervous Tissue 439

12.1 Overview of the Nervous System 440

12.2 Properties of Neurons 44112.3 Supportive Cells (Neuroglia) 44612.4 Electrophysiology of Neurons 45112.5 Synapses 460

12.6 Neural Integration 466

Connective Issues 474 Study Guide 475

The Spinal Cord, Spinal Nerves, and Somatic Reflexes 478

13.1 The Spinal Cord 47913.2 The Spinal Nerves 48713.3 Somatic Reflexes 500

Study Guide 508

Chapter 14The Brain and Cranial Nerves 511

14.1 Overview of the Brain 51214.2 Meninges, Ventricles, Cerebrospinal Fluid, and Blood Supply 516

14.3 The Hindbrain and Midbrain 52114.4 The Forebrain 528

14.5 Integrative Functions of the Brain 534

14.6 The Cranial Nerves 546

Study Guide 558

Chapter 15The Autonomic Nervous System and Visceral Reflexes 561

15.1 General Properties of the Autonomic Nervous System 56215.2 Anatomy of the Autonomic Nervous System 565

15.3 Autonomic Effects on Target Organs 572

15.4 Central Control of Autonomic Function 577

Study Guide 579

Chapter 16Sense Organs 582

16.1 Properties and Types of Sensory Receptors 583

16.2 The General Senses 58516.3 The Chemical Senses 591

Study Guide 629

Chapter 17

The Endocrine System 633

17.1 Overview of the Endocrine

System 634

17.2 The Hypothalamus and Pituitary

Gland 637

17.3 Other Endocrine Glands 645

17.4 Hormones and Their Actions 655

17.5 Stress and Adaptation 665

17.6 Eicosanoids and Paracrine

19.1 Overview of the Cardiovascular System 715

19.2 Gross Anatomy of the Heart 71719.3 Cardiac Muscle and the Cardiac Conduction System 72519.4 Electrical and Contractile Activity of the Heart 728

19.5 Blood Flow, Heart Sounds, and the Cardiac Cycle 734

19.6 Cardiac Output 740

Study Guide 746

Chapter 20The Circulatory System: Blood Vessels and Circulation 749

20.1 General Anatomy of the Blood Vessels 750

20.2 Blood Pressure, Resistance, and Flow 758

20.3 Capillary Exchange 76520.4 Venous Return and Circulatory Shock 769

20.5 Special Circulatory Routes 77120.6 Anatomy of the Pulmonary Circuit 772

20.7 Systemic Vessels of the Axial Region 773

20.8 Systemic Vessels of the Appendicular Region 792

Connective Issues 803 Study Guide 804

The Lymphatic and Immune Systems 808

21.1 The Lymphatic System 80921.2 Nonspecific Resistance 82221.3 General Aspects of Specific Immunity 830

21.4 Cellular Immunity 83421.5 Humoral Immunity 83721.6 Immune System Disorders 843

Connective Issues 849 Study Guide 850

Chapter 22The Respiratory System 854

22.1 Anatomy of the Respiratory System 855

22.2 Pulmonary Ventilation 86622.3 Gas Exchange and Transport 87722.4 Respiratory Disorders 887

Connective Issues 891 Study Guide 892

Chapter 23The Urinary System 895

23.1 Functions of the Urinary System 896

23.2 Anatomy of the Kidney 89823.3 Urine Formation I: Glomerular Filtration 904

23.4 Urine Formation II: Tubular Reabsorption and Secretion 91023.5 Urine Formation III: Water Conservation 914

23.6 Urine and Renal Function Tests 91823.7 Urine Storage and Elimination 920

Connective Issues 926 Study Guide 927

xxiv

Water, Electrolyte, and Acid–Base

The Digestive System 953

25.1 General Anatomy and Digestive

Processes 95425.2 The Mouth Through Esophagus 958

25.3 The Stomach 965

25.4 The Liver, Gallbladder, and

Pancreas 97425.5 The Small Intestine 980

25.6 Chemical Digestion and

Absorption 98425.7 The Large Intestine 990

26.3 Lipid and Protein Metabolism 1020

26.4 Metabolic States and Metabolic

Rate 102326.5 Body Heat and

Thermoregulation 1025

Study Guide 1030

Reproduction and Development

Chapter 27The Male Reproductive System 1034

27.1 Sexual Reproduction and Development 103527.2 Male Reproductive Anatomy 104027.3 Puberty and Climacteric 1047 27.4 Sperm and Semen 105027.5 Male Sexual Response 1055

Study Guide 1061

Chapter 28The Female Reproductive System 1064

28.1 Reproductive Anatomy 106528.2 Puberty and Menopause 107528.3 Oogenesis and the Sexual Cycle 1077

28.4 Female Sexual Response 108528.5 Pregnancy and Childbirth 108628.6 Lactation 1093

Connective Issues 1098 Study Guide 1099

Human Development and Aging 1102

29.1 Fertilization and the Preembryonic Stage 1103

29.2 The Embryonic and Fetal Stages 1109

29.3 The Neonate 111929.4 Aging and Senescence 1124

Appendix D: Biomedical Abbreviations A-14 Glossary G-1

Credits C-1 Index I-1

Letter to the Students

When I was a young boy, I became interested in

what I then called “nature study” for two sons One was the sheer beauty of nature I rev-eled in children’s books with abundant, colorful drawings

rea-and photographs of animals, plants, minerals, rea-and gems

It was this esthetic appreciation of nature that made me

want to learn more about it and made me happily

sur-prised to discover I could make a career of it At a slightly

later age, another thing that drew me still deeper into

biology was to discover writers who had a way with

words—who could captivate my imagination and

curios-ity with their elegant prose Once I was old enough to

hold part-time jobs, I began buying zoology and

anato-my books that mesmerized me with their gracefulness of

writing and fascinating art and photography I wanted to

write and draw like that myself, and I began teaching

myself by learning from “the masters.” I spent many late

nights in my room peering into my microscope and jars

of pond water, typing page after page of manuscript, and

trying pen and ink as a medium In short, I was the

ultimate nerd My “first book” was a 318-page paper on

some little pond animals called hydras, with 53 India ink

illustrations that I wrote for my tenth-grade biology class

when I was 16

Fast-forward about 30 years, to when I became a

textbook writer, and I found myself bringing that same

enjoyment of writing and illustrating to the first edition of

this book you are now holding Why? Not only for its

intrinsic creative satisfaction, but because I’m guessing

that you’re like I was—you can appreciate a book that

does more than simply give you the information you

need You appreciate, I trust, a writer who makes it

enjoy-able for you through his scientific, storytelling prose and

his concept of the way things should be illustrated to

spark interest and facilitate understanding

I know from my own students, however, that you need more than captivating illustrations and enjoyable reading Let’s face it—A&P is a complex subject and it may seem a formidable task to acquire even a basic knowledge of the human body It was difficult even for me

to learn (and the learning never ends) So in addition to simply writing this book, I’ve given a lot of thought to its pedagogy—the art of teaching I’ve designed my chapters

to make them easier for you to study and to give you abundant opportunity to check whether you’ve under-stood what you read—to test yourself (as I advise my own students) before the instructor tests you

Each chapter is broken down into short, digestible bits with a set of Expected Learning Outcomes at the beginning of each section, and self-testing questions (Before You Go On) just a few pages later Even if you have just 30 minutes to read during a lunch break or a bus ride, you can easily read or review one of these brief sec-tions There are also numerous self-testing questions at the end of each chapter, in some of the figure legends, and the occasional Apply What You Know questions dis-persed throughout each chapter The questions cover a broad range of cognitive skills, from simple recall of a term to your ability to evaluate, analyze, and apply what you’ve learned to new clinical situations or other prob-lems

I hope you enjoy your study of this book, but I know there are always ways to make it even better Indeed, what quality you may find in this edition owes a great deal to feedback I’ve received from students all over the world If you find any typos or other errors, if you have any suggestions for improvement, if I can clarify a con-cept for you, or even if you just want to comment on some-thing you really like about the book, I hope you’ll feel free

to write to me I correspond quite a lot with students and would enjoy hearing from you

Ken Saladin

Georgia College & State UniversityMilledgeville, GA 31061 (USA)ken.saladin@gcsu.edu

xxvi

W W W A P R E V E A L E D.C O M

An Interactive Cadaver Dissection Experience

This unique multimedia tool is designed to help you master human anatomy and physiology with:

my y

my

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concepts, and instructors can access specifi c LearnSmart

reports to monitor progress For more information, go to

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McGraw-Hill ConnectPlus TM Anatomy & Physiology

interactive learning platform provides a customizable,

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Learn more at www.mcgrawhillconnect.com

Full Textbook Integration!

Icons throughout the book indicate specifi c McGraw-Hill Anatomy & Physiology|REVEALED® 3.0 content that corresponds to the text and fi gures

Students can navigate directly from the ConnectPlus eBook to related APR content.

Instructors can assign APR within the ConnectPlus eBook.

Students can navigate directly from the ConnectPlus eBook to

LEXICON OF BIOMEDICAL WORD ELEMENTS

a- no, not, without (atom, agranulocyte) ab- away (abducens, abduction) acetabulo- small cup (acetabulum) acro- tip, extremity, peak (acromion,

temporal)

ala- wing (ala nasi) albi- white (albicans, linea alba, albino) algi- pain (analgesic, myalgia)

aliment- nourishment (alimentary) allo- other, different (allele, allograft) amphi- both, either (amphiphilic,

-ata, -ate 1 possessing (hamate, corniculate)

2 plural of -a (stomata, carcinomata)

athero- fat (atheroma, atherosclerosis) atrio- entryway (atrium, atrioventricular) auri- ear (auricle, binaural)

auto- self (autolysis, autoimmune) axi- axis, straight line (axial, axoneme, axon) baro- pressure (baroreceptor, hyperbaric) bene- good, well (benign, beneficial) bi- two (bipedal, biceps, bifid)

bili- bile (biliary, bilirubin) bio- life, living (biology, biopsy, microbial) blasto- precursor, bud, producer (fibroblast,

celi- belly, abdomen (celiac) centri- center, middle (centromere,

centriole)

cephalo- head (cephalic, encephalitis) cervi- neck, narrow part (cervix, cervical) chiasm- cross, X (optic chiasm)

choano- funnel (choana) chole- bile (cholecystokinin,

cholelithotripsy)

chondro- 1 grain (mitochondria)

2 cartilage, gristle (chondrocyte,

cisterna reservoir (cisterna chyli) clast- break down, destroy (osteoclast) clavi- hammer, club, key (clavicle,

supraclavicular)

-cle little (tubercle, corpuscle) cleido- clavicle (sternocleidomastoid) cnemo- lower leg (gastrocnemius) co- together (coenzyme, cotransport) collo- 1 hill (colliculus) 2 glue (colloid,

collagen)

contra- opposite (contralateral) corni- horn (cornified, corniculate, cornu) corono- crown (coronary, corona, coronal) corpo- body (corpus luteum, corpora

quadrigemina)

corti- bark, rind (cortex, cortical) costa- rib (intercostal, subcostal) coxa- hip (os coxae, coxal) crani- helmet (cranium, epicranius) cribri- sieve, strainer (cribriform, area

auricular)

cune- wedge (cuneiform, cuneatus) cutane-, cuti- skin (subcutaneous, cuticle) cysto- bladder (cystitis, cholecystectomy) cyto- cell (cytology, cytokinesis, monocyte) de- down (defecate, deglutition,

dehydration)

demi- half (demifacet, demilune) den-, denti- tooth (dentition, dens, dental) dendro- tree, branch (dendrite,

dia- 1 across, through, separate

(diaphragm, dialysis) 2 day (circadian)

dis- 1 apart (dissect, dissociate) 2 opposite,

absence (disinfect, disability)

diure- pass through, urinate (diuretic, diuresis) dorsi- back (dorsal, dorsum, latissimus dorsi) duc- to carry (duct, adduction, abducens) dys- bad, abnormal, painful (dyspnea,

dystrophy)

e- out (ejaculate, eversion) -eal pertaining to (hypophyseal, arboreal)

ob- 1 life (aerobic, microbe) 2 against,

toward, before (obstetrics, obturator, obstruction)

oculo- eye (oculi, oculomotor) odonto- tooth (odontoblast, periodontal) -oid like, resembling (colloid, sigmoid,

onychomycosis)

op- vision (optics, myopia, photopic) -opsy viewing, to see (biopsy, rhodopsin) or- mouth (oral, orbicularis oris) orbi- circle (orbicularis, orbit) organo- tool, instrument (organ, organelle) ortho- straight (orthopnea, orthodontics,

orthopedics)

-ose 1 full of (adipose) 2 sugar (sucrose,

glucose)

-osis 1 process (osmosis, exocytosis)

2 condition, disease (cyanosis,

thrombosis) 3 increase (leukocytosis)

osmo- push (osmosis, chemiosmotic) osse-, oste- bone (osseous, osteoporosis) oto- ear (otolith, otitis, parotid)

-ous 1 full of (nitrogenous, edematous)

2 pertaining to (mucous, nervous)

3 like, characterized by (squamous,

plasm- shaped, molded (cytoplasm,

endoplasmic)

plasti- form (thromboplastin) platy- flat (platysma) pnea- breath, breathing (eupnea, dyspnea) pneumo- air, breath, lung (pneumonia,

-ptosis dropping, falling, sagging (apoptosis,

nephroptosis)

puncto- point (puncta) pyro- fire (pyrogen, antipyretic) quadri- four (quadriceps, quadratus) quater- fourth (quaternary)

radiat- radiating (corona radiata) rami- branch (ramus)

recto- straight (rectus abdominis, rectum) reno- kidney (renal, renin)

reti- network (reticular, rete testis) retinac- retainer, bracelet (retinaculum) retro- behind, backward (retroperitoneal,

sarco- flesh, muscle (sarcoplasm, sarcomere) scala- staircase (scala tympani)

sclero- hard, tough (sclera, sclerosis) scopo- see (microscope, endoscopy) secto- cut (section, dissection) semi- half (semilunar, semimembranosus) sepsi- infection (asepsis, septicemia) -sis process (diapedesis, amniocentesis) sole- sandal, sole of foot, flatfish (sole, soleus) soma-, somato- body (somatic, somatotropin) spheno- wedge (sphenoid)

spiro- breathing (inspiration, spirometry) splanchno- viscera (splanchnic) spleno- 1 bandage (splenius capitis)

2 spleen (splenic artery) squamo- scale, flat (squamous,

supra- above (supraspinous, supraclavicular) sura- calf of leg (triceps surae)

sym- together (sympathetic, symphysis) syn- together (synostosis, syncytium) tachy- fast (tachycardia, tachypnea) tarsi- ankle (tarsus, metatarsal) tecto- roof, cover (tectorial membrane,

tomo- 1 cut (tomography, atom, anatomy)

2 segment (dermatome, myotome,

(trapezium) 2 trapezoid (trapezius)

tri- three (triceps, triglyceride) tricho- hair (trichosiderin, peritrichial) trocho- wheel, pulley (trochlea) troph- 1 food, nourishment (trophic,

trophoblast) 2 growth (dystrophy,

vagino- sheath (invaginate, tunica vaginalis) vago- wander (vagus)

vaso- vessel (vascular, vas deferens, vasa

recta)

ventro- belly, lower part (ventral, ventricle) vermi- worm (vermis, vermiform appendix) vertebro- spine (vertebrae, intervertebral) vesico- bladder, blister (vesical, vesicular) villo- hair, hairy (microvillus)

vitre- glass (in vitro, vitreous humor) vivi- life, alive (in vivo, revive) zygo- union, join, mate (zygomatic, zygote,

azygos)

ec-, ecto- outside, out of, external (ectopic,

ectoderm, splenectomy)

ef- out of (efferent, effusion)

-el, -elle small (fontanel, organelle, micelle)

electro- electricity (electrocardiogram,

electrolyte)

em- in, within (embolism, embedded)

emesi-, emeti- vomiting (emetic, hyperemesis)

-emia blood condition (anemia, hypoxemia)

en- in, into (enzyme, parenchyma)

encephalo- brain (encephalitis,

entero- gut, intestine (mesentery, myenteric)

epi- upon, above (epidermis, epiphysis,

epididymis)

ergo- work, energy, action (allergy, adrenergic)

eryth-, erythro- red (erythema, erythrocyte)

esthesio- sensation, feeling (anesthesia,

somesthetic)

eu- good, true, normal, easy (eupnea,

aneuploidy)

exo- out (exopeptidase, exocytosis, exocrine)

facili- easy (facilitated)

fasci- band, bundle (fascia, fascicle)

fenestr- window (fenestrated)

fer- to carry (efferent, uriniferous)

ferri- iron (ferritin, transferrin)

fibro- fiber (fibroblast, fibrosis)

fili- thread (myofilament, filiform)

flagello- whip (flagellum)

foli- leaf (folic acid, folia)

-form shape (cuneiform, fusiform)

fove- pit, depression (fovea)

funiculo- little rope, cord (funiculus)

fusi- 1 spindle (fusiform) 2 pour out

(perfusion)

gamo- marriage, union (monogamy, gamete)

gastro- belly, stomach (gastrointestinal,

digastric)

-gen, -genic, -genesis producing, giving rise

to (pathogen, carcinogenic, glycogenesis)

genio- chin (geniohyoid, genioglossus)

germi- 1 sprout, bud (germinal,

germinativum) 2 microbe (germicide)

gero- old age (progeria, geriatrics,

gerontology)

gesto- 1 to bear, carry (ingest) 2 pregnancy

(gestation, progesterone)

glia- glue (neuroglia, microglia)

globu- ball, sphere (globulin, hemoglobin)

glom- ball (glomerulus)

glosso- tongue (glossopharyngeal,

hypoglossal)

glyco- sugar (glycogen, glycolysis,

hypoglycemia)

gono- 1 angle, corner (trigone) 2 seed,

sex cell, generation (gonad, oogonium,

gonorrhea)

gradi- walk, step (retrograde, gradient)

-gram recording of (electrocardiogram,

(homeostasis, homeothermic)

homo- same, alike (homologous, homozygous) hyalo- clear, glassy (hyaline, hyaluronic acid) hydro- water (dehydration, hydrolysis,

hydrophobic)

hyper- above, above normal, excessive

(hyperkalemia, hypertonic)

hypo- below, below normal, deficient

(hypogastric, hyponatremia, hypophysis)

-ia condition (anemia, hypocalcemia,

ischi- to hold back (ischium, ischemia) -ism 1 process, state, condition

(metabolism, rheumatism) 2 doctrine,

belief, theory (holism, reductionism, naturalism)

iso- same, equal (isometric, isotonic, isomer) -issimus most, greatest (latissimus,

longissimus)

-ite little (dendrite, somite) -itis inflammation (dermatitis, gingivitis) jug- to join (conjugated, jugular) juxta- next to (juxtamedullary,

lati- broad (fascia lata, latissimus dorsi)

-lemma husk (sarcolemma, neurilemma) lenti- lens (lentiform)

-let small (platelet) leuko- white (leukocyte, leukemia) levato- to raise (levator labii, elevation) ligo- to bind (ligand, ligament)

line- line (linea alba, linea nigra) litho- stone (otolith, lithotripsy) -logy study of (histology, physiology,

malformed)

malle- hammer (malleus, malleolus) mammo- breast (mammary, mammillary) mano- hand (manus, manipulate) manubri- handle (manubrium) masto- breast (mastoid, gynecomastia) medi- middle (medial, mediastinum,

intermediate)

medullo- marrow, pith (medulla) mega- large (megakaryocyte, hepatomegaly) melano- black (melanin, melanocyte,

metri- 1 length, measure (isometric,

emmetropic) 2 uterus (endometrium)

micro- small (microscopic, microcytic,

Module 1: Body Orientation

1

CHAPTER OUTLINE

1.1 The Scope of Anatomy and Physiology 2

• Anatomy—The Study of Form 2

• Physiology—The Study of Function 3

1.2 The Origins of Biomedical Science 3

• The Greek and Roman Legacy 3

• The Birth of Modern Medicine 4

• Living in a Revolution 6

1.3 Scientific Method 7

• The Inductive Method 7

• The Hypothetico–Deductive Method 8

• Experimental Design 8

• Peer Review 8

• Facts, Laws, and Theories 9

1.4 Human Origins and Adaptations 9

• Evolution, Selection, and Adaptation 10

• Our Basic Primate Adaptations 10

• Homeostasis and Negative Feedback 16

• Positive Feedback and Rapid Change 18

1.7 The Language of Medicine 20

• The History of Anatomical Terminology 20

• Analyzing Medical Terms 20

• Plural, Adjectival, and Possessive Forms 21

• Pronunciation 22

• The Importance of Precision 22

1.8 Review of Major Themes 22 Study Guide 25

A new life begins—a human embryo on the point of a pin

MAJOR THEMES

OF ANATOMY AND PHYSIOLOGY

1

No branch of science hits as close to home as the science of

our own bodies We’re grateful for the dependability of our

hearts; we’re awed by the capabilities of muscles and joints

displayed by Olympic athletes; and we ponder with philosophers

the ancient mysteries of mind and emotion We want to know how

our body works, and when it malfunctions, we want to know what

is happening and what we can do about it Even the most ancient

writings of civilization include medical documents that attest to

humanity’s timeless drive to know itself You are embarking on a

subject that is as old as civilization, yet one that grows by thousands

of scientific publications every week

This book is an introduction to human structure and function,

the biology of the human body It is meant primarily to give you a

foundation for advanced study in health care, exercise physiology,

pathology, and other fields related to health and fitness Beyond

that purpose, however, it can also provide you with a deeply

satisfying sense of self-understanding

As rewarding and engrossing as this subject is, the human body

is highly complex, and understanding it requires us to comprehend

a great deal of detail The details will be more manageable if we

relate them to a few broad, unifying concepts The aim of this

chapter, therefore, is to introduce such concepts and put the rest of

the book into perspective We consider the historical development

of anatomy and physiology, the thought processes that led to

the knowledge in this book, the meaning of human life, a central

concept of physiology called homeostasis, and how to better

understand medical terminology

Physiology

Expected Learning Outcomes

When you have completed this section, you should be able to

a define anatomy and physiology and relate them to each

other;

b describe several ways of studying human anatomy; and

c define a few subdisciplines of human physiology

Anatomy is the study of structure, and physiology is the

study of function These approaches are complementary

and never entirely separable Together, they form the

bed-rock of the health sciences When we study a structure,

we want to know, What does it do? Physiology thus lends

meaning to anatomy; and, conversely, anatomy is what

makes physiology possible This unity of form and

func-tion is an important point to bear in mind as you study the

body Many examples of it will be apparent throughout

the book—some of them pointed out for you, and others

you will notice for yourself

Anatomy—The Study of Form

There are several ways to examine the structure of the human body The simplest is inspection—simply looking at

the body’s appearance, as in performing a physical tion or making a clinical diagnosis from surface appearance

examina-Physical examinations also involve touching and listening

to the body Palpation1 means feeling a structure with the hands, such as palpating a swollen lymph node or taking a pulse Auscultation2 (AWS-cul-TAY-shun) is listening to the natural sounds made by the body, such as heart and lung sounds In percussion, the examiner taps on the body, feels

for abnormal resistance, and listens to the emitted sound for signs of abnormalities such as pockets of fluid or air

But a deeper understanding of the body depends

on dissection (dis-SEC-shun)—the careful cutting and

separation of tissues to reveal their relationships The

very words anatomy3 and dissection4 both mean “cutting apart”; until the nineteenth century, dissection was called

“anatomizing.” In many schools of health science, one of the first steps in the training of students is dissection of the cadaver,5 a dead human body (fig 1.1) Many insights into human structure are obtained from comparative anatomy—the study of more than one species in order

to examine structural similarities and differences and analyze evolutionary trends Anatomy students often begin by dissecting other animals with which we share a common ancestry and many structural similarities Many

of the reasons for human structure become apparent only when we look at the structure of other animals

1 palp = touch, feel; ation = process

2 auscult = listen; ation = process

3 ana = apart; tom = cut

4 dis = apart; sect = cut

5 from cadere = to fall down or die

Laboratory with Three Cadavers.

● Why should medical students study more than one cadaver?

Dissection, of course, is not the method of choice when studying a living person! It was once common to

diagnose disorders through exploratory surgery—opening

the body and taking a look inside to see what was wrong

and what could be done about it Any breach of the body

cavities is risky, however, and most exploratory surgery

has now been replaced by medical imaging techniques—

methods of viewing the inside of the body without

surgery, discussed at the end of this chapter (see Deeper

Insight 1.5) The branch of medicine concerned with

imag-ing is called radiology Structure that can be seen with the

naked eye—whether by surface observation, radiology, or

dissection—is called gross anatomy.

Ultimately, the functions of the body result from its individual cells To see those, we usually take tissue

specimens, thinly slice and stain them, and observe them

under the microscope This approach is called histology6

(microscopic anatomy) Histopathology is the microscopic

examination of tissues for signs of disease Cytology7 is the

study of the structure and function of individual cells

Ultrastructure refers to fine detail, down to the molecular

level, revealed by the electron microscope

Physiology—The Study of Function

Physiology 8 uses the methods of experimental science

discussed later It has many subdisciplines such as

neu-rophysiology (physiology of the nervous system),

endo-crinology (physiology of hormones), and pathophysiology

(mechanisms of disease) Partly because of limitations on

experimentation with humans, much of what we know

about bodily function has been gained through

compara-tive physiology, the study of how different species have

solved problems of life such as water balance,

respira-tion, and reproduction Comparative physiology is also

the basis for the development of new drugs and medical

procedures For example, a cardiac surgeon may have to

learn animal surgery before practicing on humans, and

a vaccine cannot be used on human subjects until it has

been demonstrated through animal research that it

con-fers significant benefits without unacceptable risks

Before You Go On

Answer the following questions to test your understanding of the

preceding section:

1 What is the difference between anatomy and physiology? How

do these two sciences support each other?

2 Name the method that would be used for each of the

follow-ing: listening to a patient for a heart murmur; studying the microscopic structure of the liver; microscopically examining liver tissue for signs of hepatitis; learning the blood vessels of

a cadaver; and performing a breast self-examination.

Science

Expected Learning Outcomes

When you have completed this section, you should be able to

a give examples of how modern biomedical science emerged from an era of superstition and authoritarianism; and

b describe the contributions of some key people who helped to bring about this transformation

Any science is more enjoyable if we consider not just the current state of knowledge, but how it compares to past understandings of the subject and how our knowledge was gained Of all sciences, medicine has one of the most fasci-nating histories Medical science has progressed far more

in the last 50 years than in the 2,500 years before that, but the field did not spring up overnight It is built upon centuries of thought and controversy, triumph and defeat

We cannot fully appreciate its present state without standing its past—people who had the curiosity to try new things, the vision to look at human form and function in new ways, and the courage to question authority

under-The Greek and Roman Legacy

As early as 3,000 years ago, physicians in Mesopotamia and Egypt treated patients with herbal drugs, salts, physical therapy, and faith healing The “father of medicine,” how-ever, is usually considered to be the Greek physician Hippo- crates (c 460–c 375 BCE) He and his followers established

a code of ethics for physicians, the Hippocratic Oath, that

is still recited in modern form by many graduating medical students Hippocrates urged physicians to stop attributing disease to the activities of gods and demons and to seek their natural causes, which could afford the only rational basis for therapy

Aristotle (384–322 BCE) was one of the first phers to write about anatomy and physiology He believed that diseases and other natural events could have either

philoso-supernatural causes, which he called theologi, or natural ones, which he called physici or physiologi We derive such terms as physician and physiology from the latter Until

the nineteenth century, physicians were called “doctors

of physic.” In his anatomy book, On the Parts of Animals,

Aristotle tried to identify unifying themes in nature Among other points, he argued that complex structures are built from a smaller variety of simple components—a per-spective that we will find useful later in this chapter

Apply What You Know

When you have completed this chapter, discuss the vance of Aristotle’s philosophy to our current thinking about human structure.

rele-6 histo = tissue; logy = study of

7 cyto = cell; logy = study of

8 physio = nature; logy = study of

Claudius Galen (c 130–c 200), physician to the

Roman gladiators, wrote the most influential medical

textbook of the ancient era—a book that was worshipped

to excess by medical professors for centuries to follow

Cadaver dissection was banned in Galen’s time because

of some horrid excesses that preceded him, including

public dissection of living slaves and prisoners Aside

from what he could learn by treating the gladiators’

wounds, Galen was therefore limited to dissecting pigs,

monkeys, and other animals Because he was not

per-mitted to dissect cadavers, he had to guess at much of

human anatomy and made some incorrect deductions

from animal dissections He described the human liver,

for example, as having five fingerlike lobes, somewhat

like a baseball glove, because that is what he had seen in

baboons But Galen saw science as a method of

discov-ery, not as a body of fact to be taken on faith He warned

that even his own books could be wrong and advised

his followers to trust their own observations more than

they trusted any book Unfortunately, his advice was not

heeded For nearly 1,500 years, medical professors

dog-matically taught what they read in Aristotle and Galen,

seldom daring to question the authority of these “ancient

masters.”

The Birth of Modern Medicine

In the Middle Ages, the state of medical science varied

greatly from one religious culture to another Science was

severely repressed in the Christian culture of Europe until

about the sixteenth century, although some of the most

famous medical schools of Europe were founded during

this era Their professors, however, taught medicine

pri-marily as a dogmatic commentary on Galen and Aristotle,

not as a field of original research Medieval medical

illus-trations were crude representations of the body intended

more to decorate a page than to depict the body

realisti-cally Some were astrological charts that showed which

sign of the zodiac was thought to influence each organ

of the body (fig 1.2) From such pseudoscience came the

word influenza, Italian for “influence.”

Free inquiry was less inhibited in Jewish and Muslim

culture during this time Jewish physicians were the

most esteemed practitioners of their art—and none more

famous than Moses ben Maimon (1135–1204), known in

Christendom as Maimonides Born in Spain, he fled to

Egypt at age 24 to escape antisemitic persecution There

he served the rest of his life as physician to the court of

the sultan, Saladin A highly admired rabbi, Maimonides

wrote voluminously on Jewish law and theology, but also

wrote 10 influential medical books and numerous treatises

on specific diseases

Among Muslims, probably the most highly regarded

medical scholar was Ibn Sina (980–1037), known in the West

as Avicenna or “the Galen of Islam.” He studied Galen and

Aristotle, combined their findings with original discoveries,

and questioned authority when the evidence demanded it

Medicine in the Mideast soon became superior to European

medicine Avicenna’s textbook, The Canon of Medicine, was

the leading authority in European medical schools for over

500 years

Chinese medicine had little influence on Western thought and practice until relatively recently; the medical arts evolved in China quite independently of European medicine Later chapters of this book describe some of the medical and anatomical insights of ancient China and India

Modern Western medicine began around the sixteenth century in the innovative minds of such people as the anatomist Andreas Vesalius and the physi-ologist William Harvey Andreas Vesalius (1514–64)

medical manuscript reflects the medieval belief in the influence of astrology on parts of the body.

● How does the word influenza stem from the belief reflected by this illustration?

taught anatomy in Italy In his time, the Catholic Church

relaxed its prohibition against cadaver dissection,

pri-marily to allow autopsies in cases of suspicious death

Furthermore, the Italian Renaissance created an

environ-ment more friendly to innovative scholarship Dissection

gradually found its way into the training of medical

stu-dents throughout Europe It was an unpleasant business,

however, and most professors considered it beneath their

dignity In those days before refrigeration or embalming,

the odor from the decaying cadaver was unbearable

Dissections were conducted outdoors in a nonstop 4-day

race against decay Bleary medical students had to fight

the urge to vomit, lest they incur the wrath of an

over-bearing professor Professors typically sat in an elevated

chair, the cathedra, reading dryly in Latin from Galen or

Aristotle while a lower-ranking barber–surgeon removed

putrefying organs from the cadaver and held them up

for the students to see Barbering and surgery were

con-sidered to be “kindred arts of the knife”; today’s barber

poles date from this era, their red and white stripes

symbolizing blood and bandages

Vesalius broke with tradition by coming down from the cathedra and doing the dissections himself He was

quick to point out that much of the anatomy in Galen’s

books was wrong, and he was the first to publish accurate

illustrations for teaching anatomy (fig 1.3) When others

began to plagiarize his illustrations, Vesalius published

the first atlas of anatomy, De Humani Corporis Fabrica

(On the Structure of the Human Body), in 1543 This book

began a rich tradition of medical illustration that has been

handed down to us through such milestones as Gray’s

Anatomy (1856) and the vividly illustrated atlases and

textbooks of today

Anatomy preceded physiology and was a necessary foundation for it What Vesalius was to anatomy, the

Englishman William Harvey (1578–1657) was to

physiol-ogy Harvey is remembered especially for his studies of

blood circulation and a little book he published in 1628,

known by its abbreviated title De Motu Cordis (On the

were the first Western scientists to realize that blood must

circulate continuously around the body, from the heart

to the other organs and back to the heart again This flew

in the face of Galen’s belief that the liver converted food

to blood, the heart pumped blood through the veins to

all other organs, and those organs consumed it Harvey’s

colleagues, wedded to the ideas of Galen, ridiculed him

for his theory, though we now know he was correct (see

p 750) Despite persecution and setbacks, Harvey lived

to a ripe old age, served as physician to the kings of

England, and later did important work in embryology

Most importantly, Harvey’s contributions represent the

birth of experimental physiology—the method that

gener-ated most of the information in this book

Modern medicine also owes an enormous debt to two inventors from this era, Robert Hooke and Antony van

Leeuwenhoek, who extended the vision of biologists to the cellular level

Robert Hooke (1635–1703), an Englishman, designed

scientific instruments of various kinds and made many improvements in the compound microscope This is a tube

with a lens at each end—an objective lens near the

speci-men, which produces an initial magnified image, and an

ocular lens (eyepiece) near the observer’s eye, which

magni-fies the first image still further Although crude compound microscopes had existed since 1595, Hooke improved the optics and invented several of the helpful features found in microscopes today—a stage to hold the specimen, an illumi-nator, and coarse and fine focus controls His microscopes magnified only about 30 times, but with them, he was the first to see and name cells In 1663, he observed thin shav-ings of cork and observed that they “consisted of a great

many little boxes,” which he called cellulae (little cells) after

medical illustration with the comparatively realistic art prepared for his

1543 book, De Humani Corporis Fabrica.

amus-no one in history had looked at nature in such a tionary way By taking biology to the cellular level, the two men had laid an entirely new foundation for the modern medicine to follow centuries later.

revolu-The Hooke and Leeuwenhoek microscopes produced

poor images with blurry edges (spherical aberration) and rainbowlike distortions (chromatic aberration) These

problems had to be solved before the microscope could

be widely used as a biological tool In nineteenth-century Germany, Carl Zeiss (1816–88) and his business partner,

physicist Ernst Abbe (1840–1905), greatly improved

the compound microscope, adding the condenser and developing superior optics With improved microscopes, biologists began eagerly examining a wider variety

of specimens By 1839, botanist Matthias Schleiden

(1804–81) and zoologist Theodor Schwann (1810–82)

concluded that all organisms were composed of cells

Although it took another century for this idea to be ally accepted, it became the first tenet of the cell theory,

gener-added to by later biologists and summarized in chapter 3

The cell theory was perhaps the most important through in biomedical history; all functions of the body are now interpreted as the effects of cellular activity

break-Although the philosophical foundation for ern medicine was largely established by the time of Leeuwenhoek, Hooke, and Harvey, clinical practice was still in a dismal state Few doctors attended medical school or received any formal education in basic science

mod-or human anatomy Physicians tended to be ignmod-orant, ineffective, and pompous Their practice was heavily based on expelling imaginary toxins from the body by bleeding their patients or inducing vomiting, sweat-ing, or diarrhea They performed operations with filthy hands and instruments, spreading lethal infections from one patient to another and refusing, in their vanity, to believe that they themselves were the carriers of disease

Countless women died of infections acquired during childbirth from their obstetricians Fractured limbs often became gangrenous and had to be amputated, and there was no anesthesia to lessen the pain Disease was still widely attributed to demons and witches, and many people felt they would be interfering with God’s will if they tried to treat it

Living in a Revolution

This short history brings us only to the threshold of modern biomedical science; it stops short of such momentous discoveries as the germ theory of disease, the mechanisms of heredity, and the structure of DNA

In the twentieth century, basic biology and biochemistry

microscope had a lens at each end of a tubular body (b) Hooke’s drawing

of cork cells, showing the thick cell walls characteristic of plants.

the cubicles of a monastery (fig 1.4) He later observed thin

slices of fresh wood and saw living cells “filled with juices.”

Hooke became particularly interested in microscopic

exami-nation of such material as insects, plant tissues, and animal

parts He published the first comprehensive book of

micros-copy, Micrographia, in 1665.

Antony van Leeuwenhoek (an-TOE-nee vahn

LAY-wen-hook) (1632–1723), a Dutch textile merchant, invented a

simple (single-lens) microscope, originally for the purpose

of examining the weave of fabrics His microscope was

a beadlike lens mounted in a metal plate equipped with a

movable specimen clip Even though his microscopes were

simpler than Hooke’s, they achieved much greater useful

magnification (up to 200×) owing to Leeuwenhoek’s

supe-rior lens-making technique Out of curiosity, he examined

a drop of lake water and was astonished to find a variety

of microorganisms—“little animalcules,” he called them,

“very prettily a-swimming.” He went on to observe

prac-tically everything he could get his hands on, including

blood cells, blood capillaries, sperm, muscular tissue, and

bacteria from tooth scrapings Leeuwenhoek began

submit-ting his observations to the Royal Society of London in

1673 He was praised at first, and his observations were

yielded a much deeper understanding of how the body

works Advances in medical imaging have enhanced our

diagnostic ability and life-support strategies We have

witnessed monumental developments in chemotherapy,

immunization, anesthesia, surgery, organ transplants, and

human genetics By the close of the twentieth century, we

had discovered the chemical “base sequence” of every

human gene and begun attempting gene therapy to treat

children born with diseases recently considered

incur-able As future historians look back on the turn of this

century, they may exult about the Genetic Revolution in

which you are now living

Several discoveries of the nineteenth and twentieth centuries, and the men and women behind them, are

covered in short historical sketches in later chapters

Yet, the stories told in this chapter are different in a

sig-nificant way The people discussed here were pioneers in

establishing the scientific way of thinking They helped

to replace superstition with an appreciation of natural

law They bridged the chasm between mystery and

medi-cation Without this intellectual revolution, those who

followed could not have conceived of the right questions

to ask, much less a method for answering them

Before You Go On

Answer the following questions to test your understanding of the

preceding section:

3 In what way did the followers of Galen disregard his advice?

How does Galen’s advice apply to you and this book?

4 Describe two ways in which Vesalius improved medical

education and set standards that remain relevant today.

5 How is our concept of human form and function today

affected by inventors from Hooke to Zeiss?

Expected Learning Outcomes

When you have completed this section, you should be able to

a describe the inductive and hypothetico–deductive

methods of obtaining scientific knowledge;

b describe some aspects of experimental design that help to

ensure objective and reliable results; and

c explain what is meant by hypothesis, fact, law, and theory

in science

Prior to the seventeenth century, science was done in a

haphazard way by a small number of isolated individuals

The philosophers Francis Bacon (1561–1626) in England

and René Descartes (1596–1650) in France envisioned

science as a far greater, systematic enterprise with

enor-mous possibilities for human health and welfare They

detested those who endlessly debated ancient philosophy without creating anything new Bacon argued against biased thinking and for more objectivity in science He outlined a systematic way of seeking similarities, differ-ences, and trends in nature and drawing useful gener-alizations from observable facts You will see echoes of Bacon’s philosophy in the discussion of scientific method that follows

Though the followers of Bacon and Descartes argued bitterly with one another, both men wanted science to become a public, cooperative enterprise, supported by governments and conducted by an international com-munity of scholars rather than a few isolated amateurs Inspired by their vision, the French and English govern-ments established academies of science that still flourish today Bacon and Descartes are credited with putting science on the path to modernity, not by discovering anything new in nature or inventing any techniques—for neither man was a scientist—but by inventing new habits

vational procedures than to certain habits of disciplined creativity, careful observation, logical thinking, and hon-est analysis of one’s observations and conclusions It is especially important in health science to understand these habits This field is littered with more fads and frauds than any other We are called upon constantly to judge which claims are trustworthy and which are bogus

To make such judgments depends on an appreciation of how scientists think, how they set standards for truth, and why their claims are more reliable than others

The Inductive Method

The inductive method, first prescribed by Bacon, is a

process of making numerous observations until one feels confident in drawing generalizations and predictions from them What we know of anatomy is a product of the inductive method We describe the normal structure of the body based on observations of many bodies

This raises the issue of what is considered proof in science We can never prove a claim beyond all possible refutation We can, however, consider a statement as

proven beyond reasonable doubt if it was arrived at by

reliable methods of observation, tested and confirmed repeatedly, and not falsified by any credible observa-tion In science, all truth is tentative; there is no room for dogma We must always be prepared to abandon yester-day’s truth if tomorrow’s facts disprove it

The Hypothetico–Deductive Method

Most physiological knowledge was obtained by the

hypothetico–deductive method An investigator begins

by asking a question and formulating a hypothesis—an

educated speculation or possible answer to the question

A good hypothesis must be (1) consistent with what is

already known and (2) capable of being tested and possibly

falsified by evidence Falsifiability means that if we claim

something is scientifically true, we must be able to specify

what evidence it would take to prove it wrong If nothing

could possibly prove it wrong, then it is not scientific

Apply What You Know

The ancients thought that gods or invisible demons caused

epilepsy Today, epileptic seizures are attributed to bursts

of abnormal electrical activity in nerve cells of the brain

Explain why one of these claims is falsifiable (and thus

scientific), whereas the other claim is not.

The purpose of a hypothesis is to suggest a method for

answer ing a question From the hypothesis, a researcher

makes a deduction, typically in the form of an “if– then”

pre-diction: If my hypothesis on epilepsy is correct and I record

the brain waves of patients during seizures, then I  should

observe abnormal bursts of activity A properly

conduct-ed experiment yields observations that either support a

hypothesis or require the scientist to modify or abandon it,

formulate a better hypothesis, and test that one Hypothesis

testing operates in cycles of conjecture and disproof until

one is found that is supported by the evidence

Experimental Design

Doing an experiment properly involves several important

considerations What shall I measure and how can I

mea-sure it? What effects should I watch for and which ones

should I ignore? How can I be sure that my results are due

to the factors (variables) that I manipulate and not due to

something else? When working on human subjects, how

can I prevent the subject’s expectations or state of mind

from influencing the results? Most importantly, how can

I eliminate my own biases and be sure that even the most

skeptical critics will have as much confidence in my

con-clusions as I do? Several elements of experimental design

address these issues:

• Sample size The number of subjects (animals or

people) used in a study is the sample size An

adequate sample size controls for chance events and

individual variations in response and thus enables us

to place more confidence in the outcome For

exam-ple, would you rather trust your health to a drug that

was tested on 5 people or one tested on 5,000? Why?

• Controls Biomedical experiments require comparison

between treated and untreated individuals so that

we can judge whether the treatment has any effect

A control group consists of subjects that are as much

like the treatment group as possible except with

respect to the variable being tested For example, there is evidence that garlic lowers blood cholesterol levels In one study, volunteers with high cholesterol were each given 800 mg of garlic powder daily for

4 months and exhibited an average 12% reduction in cholesterol Was this a significant reduction, and was

it due to the garlic? It is impossible to say without comparison to a control group of similar people who received no treatment In this study, the control group averaged only a 3% reduction in cholesterol, so garlic

seems to have made a difference.

• Psychosomatic effects Psychosomatic effects

(effects of the subject’s state of mind on his or her physiology) can have an undesirable effect on experimental results if we do not control for them

In drug research, it is therefore customary to give the control group a placebo (pla-SEE-bo)—a substance

with no significant physiological effect on the body

If we were testing a drug, for example, we could give the treatment group the drug and the control group identical-looking sugar tablets Neither group must know which tablets it is receiving If the two groups showed significantly different effects, we could feel confident that it did not result from a knowledge of what they were taking

• Experimenter bias In the competitive, high-stakes

world of medical research, experimenters may want certain results so much that their biases, even subconscious ones, can affect their interpretation of the data One way to control for this is the double- blind method In this procedure, neither the subject

to whom a treatment is given nor the person giving

it and recording the results knows whether that ject is receiving the experimental treatment or pla-cebo A researcher might prepare identical-looking tablets, some with the drug and some with placebo;

sub-label them with code numbers; and distribute them

to participating physicians The physicians selves do not know whether they are administering drug or placebo, so they cannot give the subjects even accidental hints of which substance they are taking When the data are collected, the researcher can correlate them with the composition of the tablets and determine whether the drug had more effect than the placebo

them-• Statistical testing If you tossed a coin 100 times,

you would expect it to come up about 50 heads and 50 tails If it actually came up 48:52, you would probably attribute this to random error rather than bias in the coin But what if it came

up 40:60? At what point would you begin to pect bias? This type of problem is faced routinely

sus-in research—how great a difference must there be

between control and experimental groups before

we feel confident that it was due to the treatment and not merely random variation? What if a treat-ment group exhibited a 12% reduction in choles-terol level and the placebo group a 10% reduction?

Would this be enough to conclude that the ment was effective? Scientists are well grounded

treat-in statistical tests that can be applied to the data

Perhaps you have heard of the chi-square test, the

t test, or analysis of variance, for example A

typi-cal outcome of a statistitypi-cal test might be expressed,

“We can be 99.5% sure that the difference between group A and group B was due to the experimental treatment and not to random variation.” Science is grounded not in statements of absolute truth, but in statements of probability

Peer Review

When a scientist applies for funds to support a research

project or submits results for publication, the application

or manuscript is submitted to peer review—a critical

eval-uation by other experts in that field Even after a report is

published, if the results are important or unconventional,

other scientists may attempt to reproduce them to see if

the author was correct At every stage from planning to

postpublication, scientists are therefore subject to intense

scrutiny by their colleagues Peer review is one mechanism

for ensuring honesty, objectivity, and quality in science

Facts, Laws, and Theories

The most important product of scientific research is

understanding how nature works—whether it be the

nature of a pond to an ecologist or the nature of a liver cell

to a physiologist We express our understanding as facts,

laws, and theories of nature It is important to appreciate

the differences among these

A scientific fact is information that can be

indepen-dently verified by any trained person—for example, the

fact that an iron deficiency leads to anemia A law of

nature is a generalization about the predictable ways in

which matter and energy behave It is the result of

induc-tive reasoning based on repeated, confirmed observations

Some laws are expressed as concise verbal statements,

such as the law of complementary base pairing: In the

double helix of DNA, a chemical base called adenine

always pairs with one called thymine, and a base called

guanine always pairs with cytosine (see p 117) Other

laws are expressed as mathematical formulae, such as

Boyle’s law, used in respiratory physiology: Under

speci-fied conditions, the volume of a gas (V) is inversely

pro-portional to its pressure (P)—that is, V ∝ 1/P

A theory is an explanatory statement or set of statements

derived from facts, laws, and confirmed hypotheses Some

theories have names, such as the cell theory, the

fluid-mosaic theory of cell membranes, and the sliding filament

theory of muscle contraction Most, however, remain

unnamed The purpose of a theory is not only to concisely summarize what we already know but, moreover, to sug-gest directions for further study and to help predict what the findings should be if the theory is correct

Law and theory mean something different in science

than they do to most people In common usage, a law is

a rule created and enforced by people; we must obey it

or risk a penalty A law of nature, however, is a

descrip-tion; laws do not govern the universe, they describe it Laypeople tend to use the word theory for what a scientist

would call a hypothesis—for example, “I have a theory why my car won’t start.” The difference in meaning causes significant confusion when it leads people to think that a scientific theory (such as the theory of evolution)

is merely a guess or conjecture, instead of recognizing it

as a summary of conclusions drawn from a large body

of observed facts The concepts of gravity and electrons are theories, too, but this does not mean they are merely speculations

Apply What You Know

Was the cell theory proposed by Schleiden and Schwann more a product of the hypothetico–deductive method or

of the inductive method? Explain your answer.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

6 Describe the general process involved in the inductive method.

7 Describe some sources of potential bias in biomedical research

What are some ways of minimizing such bias?

8 Is there more information in an individual scientific fact or in a theory? Explain.

Expected Learning Outcomes

When you have completed this section, you should be able to

a explain why evolution is relevant to understanding human form and function;

b define evolution and natural selection;

c describe some human characteristics that can be uted to the tree-dwelling habits of earlier primates; and

d describe some human characteristics that evolved later in connection with upright walking

If any two theories have the broadest implications for understanding the human body, they are probably the cell

theory and the theory of natural selection Natural selection,

an explanation of how species originate and change

through time, was the brainchild of Charles Darwin

(1809–82)—probably the most influential biologist who

ever lived His book, On the Origin of Species by Means of

Natural Selection (1859), has been called “the book that

shook the world.” In presenting the first well-supported

theory of evolution, On the Origin of Species not only

caused the restructuring of all of biology but also

pro-foundly changed the prevailing view of our origin, nature,

and place in the universe

On the Origin of Species scarcely touched upon

human biology, but its unmistakable implications for

humans created an intense storm of controversy that

con-tinues even today In The Descent of Man (1871), Darwin

directly addressed the issue of human evolution and

emphasized features of anatomy and behavior that reveal

our relationship to other animals No understanding of

human form and function is complete without an

under-standing of our evolutionary history

Evolution, Selection, and Adaptation

Evolution simply means change in the genetic

composi-tion of a populacomposi-tion of organisms Examples include the

evolution of bacterial resistance to antibiotics, the

appear-ance of new strains of the AIDS virus, and the emergence

of new species of organisms

Natural selection is the principal theory of how

evo-lution works It states essentially this: Some individuals

within a species have hereditary advantages over their

competitors—for example, better camouflage, disease

resistance, or ability to attract mates—that enable them to

produce more offspring They pass these advantages on to

their offspring, and such characteristics therefore become

more and more common in successive generations This

brings about the genetic change in a population that

con-stitutes evolution

Natural forces that promote the reproductive success

of some individuals more than others are called

selec-tion pressures They include such things as climate,

predators, disease, competition, and the availability of

food Adaptations are features of an organism’s anatomy,

physiology, and behavior that have evolved in response to

these selection pressures and enable the organism to cope

with the challenges of its environment We will consider

shortly some selection pressures and adaptations that

were important to human evolution and make the human

body what it is today

Darwin could scarcely have predicted the

over-whelming mass of genetic, molecular, fossil, and other

evidence of human evolution that would accumulate in

the twentieth century and further substantiate his theory

A technique called DNA hybridization, for example,

sug-gests a difference of only 1.6% in DNA structure between

humans and chimpanzees Chimpanzees and gorillas

dif-fer by 2.3% DNA structure suggests that a chimpanzee’s

closest living relative is not the gorilla or any other ape—

it is Homo sapiens

Several aspects of our anatomy make little sense without an awareness that the human body has a history (see Deeper Insight 1.1) Our evolutionary relationship to other species is also important in choosing animals for biomedical research If there were no issues of cost, avail-ability, or ethics, we might test drugs on our close living relatives, the chimpanzees, before approving them for human use Their genetics, anatomy, and physiology are most similar to ours, and their reactions to drugs therefore afford the best prediction of how the human body would react On the other hand, if we had no kinship with any other species, the selection of a test species would be arbitrary; we might as well use frogs or snails In real-ity, we compromise Rats and mice are used extensively for research because they are fellow mammals with a physiology similar to ours, but they present fewer of the aforementioned issues than chimpanzees or other mam-mals do An animal species or strain selected for research

on a particular problem is called a model—for example, a

mouse model for leukemia

Our Basic Primate Adaptations

We belong to an order of mammals called the Primates, which also includes the monkeys and apes Some of our anatomical and physiological features can be traced to the earliest primates, descended from certain squirrel-sized, insect-eating, African mammals (insectivores) that took up life in the trees 55 to 60 million years ago This

arboreal9 (treetop) habitat probably afforded greater safety from predators, less competition, and a rich food

9 arbor = tree; eal = pertaining to

DEEPER INSIGHT 1.1 Evolutionary Medicine

Vestiges of Human Evolution

One of the classic lines of evidence for evolution, debated even before

Darwin was born, is vestigial organs These structures are the remnants

of organs that apparently were better developed and more functional

in the ancestors of a species They now serve little or no purpose or,

in some cases, have been converted to new functions.

Our bodies, for example, are covered with millions of hairs, each

equipped with a useless little muscle called a piloerector In other

mammals, these muscles fluff the hair and conserve heat In humans, they merely produce goose bumps Above each ear, we have three

auricularis muscles In other mammals, they move the ears to receive

sounds better or to repel flies and other pests, but most people cannot contract them at all As Darwin said, it makes no sense that humans would have such structures were it not for the fact that we came from ancestors in which they were functional.