Anatomy and physiology, the unity of form and function 3th ed k saladin (mcgraw hill, 2003) 1

Chapter 1, Major Themes of Anatomy and Physiology Here I replaced the section on human taxonomic classifi-cation with sections on anatomical and physiological variability.. Anatomy and

Thank you to the colleagues and students who have

made this textbook so successful and helped to ensure

its staying power in a very competitive textbook niche

Several people have asked me, with this book doing so

well, why I don’t retire from the classroom The answer

is that not only do I find classroom teaching the most

ful-filling aspect of my profession, but also that it is my

stu-dents who teach me how to write I work continually at

finding more and more effective ways of getting

con-cepts across to them, at turning on the light of insight

The best ideas for communicating difficult physiological

ideas often come to mind during my face-to-face

inter-actions with students, and many are the times that I have

dashed back from the lecture room to the drawing pad or

keyboard to sketch concepts for new illustrations or

write down new explanations Grading exams and

homework assignments also continually gives me new

impressions of whether I have effectively taught an idea

through my writing Thus, my students are my unwitting

writing teachers This pertains also to the students in my

“extended classroom”—students worldwide who use

the book and write to ask my help in understanding

dif-ficult concepts

What are the improvements in this edition? I

con-tinue to aim for ever-better clarity, brevity, currency, and

accuracy Physiology, especially, is a complex subject to

explain to beginning students, and I am always working

in both the lecture room and textbook to find clearer ways

to explain it Physiology also is a fast-growing field, and

it’s a challenge to keep a book up to date without it

grow-ing longer and longer After all, our lecture periods and

semesters aren’t getting any longer! So, while updating

information, I have looked for ways to make my

discus-sions more concise in each edition I also continue to

cor-rect errors as students and content experts have sent me

queries, corrections, and suggestions Accuracy is, of

course, an advantage of a seasoned textbook over a

new-comer, and this book has gained a lot of seasoning and a

little spice from my extensive correspondence with

stu-dents and colleagues

This preface describes the book’s intended audience,

how we determined what students and instructors want in

the ideal A&P textbook, what has changed in this edition

to best meet your needs, how this book differs from others,

and what supplements are available to round out the total

teaching package

Audience

This book is meant especially for students who plan topursue such careers as nursing, therapy, health education,medicine, and other health professions It is designed for

a two-semester combined anatomy and physiology courseand assumes that the reader has taken no prior collegechemistry or biology courses I also bear in mind thatmany A&P students return to college after interruptions toraise families or pursue other careers For returning stu-dents and those without college prerequisites, the earlychapters will serve as a refresher on the necessary points

of chemistry and cell biology

Many A&P students also are still developing theintellectual skills and study habits necessary for success

in a health science curriculum There are many, too, forwhom English was not their original language Therefore,

I endeavor to write in a style that is clear, concise, andenjoyable to read, and to enliven the facts of science withanalogies, clinical remarks, historical notes, biographicalvignettes, and other seasoning that will make the bookenjoyable to students and instructors alike Each chapter

is built around pedagogic strategies that will make the ject attainable for a wide range of students and instill thestudy and thinking habits conducive to success in moreadvanced courses

sub-How We Evaluated Your Needs

This book has evolved through extensive research on theneeds and likes of A&P students and instructors In devel-oping its three editions so far, we have collected evalua-tive questionnaires from reviewers; commissioneddetailed reviews from instructors using this book andthose using competing books; held focus groups fromcoast to coast in the United States, in which instructorsand students studied the book in advance, then met with

us to discuss it in depth for several hours, including how

it compared to other leading A&P textbooks; and createdpanels of A&P instructors to thoroughly analyze the entirebook and its art program These efforts have involvedmany hundreds of faculty and students and generatedthousands of pages of reviews, all of which I have readcarefully in developing my revision plans In a less formal

Preface

way, the book has improved because of the many e-mails I

receive from instructors and students worldwide who not

only tell me what they like about it, but also raise

sugges-tions for correction or improvement I’ve responded

gen-erously to these e-mails because I learn a great deal

look-ing up answers to readers’ questions, findlook-ing sources to

substantiate the book’s content, and sometimes finding

that I need to update, clarify, or correct a point

How We’ve Met Your Needs

Our research has consistently revealed that the three

qual-ities instructors value most in a textbook are, in

descend-ing order of importance, writdescend-ing style, illustration quality,

and teaching supplements I have focused my attention

especially on the first two of these and on pedagogic

fea-tures, while McGraw-Hill Higher Education has

continu-ally engaged other authors and software developers to

pro-duce a more diverse package of superb supplements for

students and instructors

Writing Style

Students benefit most from a book they enjoy reading, a

book that goes beyond presenting information to also tell

an interesting story and engage the reader with a

some-what conversational tone That was my guiding principle

in finding the right voice for the first edition, and it

remains so in this one I try to steer a middle course,

avoiding rigid formality on one hand or a chatty

conde-scending tone on the other I feel I have succeeded when

students describe the tone as friendly, engaging,

collo-quial, almost as if the author is talking to them, but not

talking down to them

In devising ways to make the writing more concise

without losing the qualities that make it interesting and

enjoyable, I have been guided by reviewers who identified

areas in need of less detail and by students who cited

cer-tain areas as especially engrossing and pleasurable to read

In this edition, I somewhat reduced the number of

bold-faced terms and the amount of vocabulary, and fine-tuned

such mechanics as sentence length, paragraph breaks, and

topic and transitional sentences for improved flow In

such difficult topics as action potentials, blood clotting,

the countercurrent multiplier, or aerobic respiration, I

think this book will compare favorably in a side-by-side

reading of competing textbooks

Illustrations

When I was a child, it was the art and photography in

biol-ogy books that most strongly inspired me to want to learn

about the subject So it comes as no surprise that students

and instructors rate the visual appeal of this book as

sec-ond only to writing style in importance I developed many

illustrative concepts not found in other books sional medical illustrators and graphic artists have ren-dered these, as well as the classic themes of A&P, in a vividand captivating style that has contributed a lot to a stu-dent’s desire to learn

Profes-As the book has evolved through these three tions, I have used larger figures and brighter colors;adopted simpler, uncluttered labeling; and continued toincorporate innovative illustrative concepts A good illus-tration conveys much more information than several times

edi-as much space filled with verbiage, and I have cut down

on the word count of the book to allow space for larger andmore informative graphics

The illustration program is more than line art I tinue to incorporate better histological photography andcadaver dissections, including many especially clear andskillful dissections commissioned specifically for this book.Several of my students have modeled for photo-graphs in this book As much as possible with the volun-teers who came forth, I have represented an ethnic variety

con-of subjects

Supplements

The third most highly rated quality is the package of ing supplements for the student and teaching aids for theinstructor Instructors have rated overhead transparenciesthe most important of all supplements, and we now includetransparencies of every item of line art in the book, andsome of the photographs and tables Included are unlabeledduplicates of many anatomical figures, useful for testing orlabeling to fit one’s individual teaching approach A full set

learn-of both labeled and unlabeled illustrations is also available

in the Instructor’s Presentation CD-ROM

Students have expressed growing enthusiasm andappreciation for the Online Learning Center and theEssential Study Partner We have continued to enrichthese media with an abundance of learning aids andresources These and other student and instructor supple-ments are listed and described on page xiii

What Sets This Book Apart?

Those who have not used or reviewed previous editionswill want to know how this book differs from others

Organization

The sequence of chapters and placement of some topics inthis book differ from others While I felt it was risky todepart from tradition in my first edition, reviewer com-ments have overwhelmingly supported my intuition thatthese represent a more logical way of presenting the

human A&P Indeed, some have written that they are

changing their teaching approach because of this book

Heredity

I treat the most basic concepts of heredity in chapter 4 rather

than waiting, as most books do, until the last chapter

Stu-dents would be ill-prepared to understand color blindness,

blood types, hemophilia, sex determination, and other topics

if they didn’t already know about such concepts as dominant

and recessive alleles, sex chromosomes, and sex linkage

Muscle Anatomy and Physiology

I treat gross anatomy of the muscular system (chapter 10)

immediately after the skeletal system and joints in order to

tie it closely to the structures on which the muscles act

and to relate muscle actions to the terminology of joint

movements This is followed by muscle physiology and

then neurophysiology so that these two topics can be

closely integrated in their discussions of synapses,

neuro-transmitters, and membrane potentials

Nervous System Chapters

Many instructors cite the nervous system as the most

dif-ficult one for students to understand, and in many

courses, it is presented in a hurry before the clock runs out

on the first semester Other A&P textbooks devote six

chapters or more to this system It is overwhelming to both

the instructor and student to cover this much material at

the end of the course I present this system in five

chap-ters, and notwithstanding my assignment of a separate

chapter to the autonomic nervous system in this edition,

this is still the most concise treatment of this system

among the similar two-semester textbooks

Urinary System

Most textbooks place the urinary system near the end

because of its anatomical association with the reproductive

system I feel that its intimate physiological ties with the

circulatory and respiratory systems are much more

impor-tant than this anatomical issue The respiratory and

uri-nary systems collaborate to regulate the pH of the body

flu-ids; the kidneys have more impact than any other organ on

blood volume and pressure; and the principles of capillary

fluid exchange should be fresh in the mind of a student

studying glomerular filtration and tubular reabsorption

Except for an unavoidable detour to discuss the lymphatic

and immune systems, I treat the respiratory and urinary

systems as soon as possible after the circulatory system

“Insight” Sidebars

Each chapter has from two to six special topic sidebars

called Insights, listed by title and page number on the

opening page of each chapter These fall into three gories: 101 clinical applications, 13 on medical history,and 9 on evolutionary medicine For a quick survey oftheir subject matter, see the lists under these three phrases

cate-in the cate-index

Clinical Applications

It is our primary task in A&P to teach the basic biology ofthe human body, not pathology Yet students want toknow the relevance of this biology—how it relates totheir career aims Furthermore, disease often gives us ourmost revealing window on the importance of normalstructure and function What could better serve than cys-tic fibrosis, for example, to drive home the importance ofmembrane ion pumps? What better than brittle bone dis-ease to teach the importance of collagen in the osseoustissue? The great majority of Insight sidebars thereforedeal with the clinical relevance of the basic biology Clin-ical content has also been enhanced by the addition of atable for each organ system that describes commonpathologies and page-references others

Medical History

I found long ago that students especially enjoyed lectures inwhich I remarked on the personal dramas that enliven thehistory of medicine Thus, I incorporated that approach into

my writing as well, emulating something that is standardfare in introductory biology textbooks but has been largelyabsent from A&P textbooks Reviews have shown that stu-dents elsewhere, like my own, especially like these stories

I have composed 13 historical and biographical vignettes tohave an especially poignant or inspiring quality, give stu-dents a more humanistic perspective on the field they’vechosen to study, and, I hope, to cultivate an appropriatelythoughtful attitude toward the discipline Historicalremarks are also scattered through the general text

Profiles of Marie Curie (p 58), Rosalind Franklin(p 132), and Charles Drew (p 694) tell of the struggles andunkind ironies of their scientific careers Some of myfavorite historical sidebars are the accounts of William Beau-mont’s digestive experiments on “the man with a hole in hisstomach” (p 977); Crawford Long’s pioneering surgical use

of ether, until then known mainly as a party drug (p 628);the radical alteration of Phineas Gage’s personality by hisbrain injury (p 538); and the testy relationship between themen who shared a Nobel Prize for the discovery of insulin,Frederick Banting and J J R MacLeod (p 671)

Evolutionary Medicine

The human body can never be fully appreciated without asense of how and why it came to be as it is Medical liter-ature since the mid-1990s has shown increasing interest in

“evolutionary medicine,” but most A&P textbooks tinue to disregard it Chapter 1 briefly introduces the con-

con-cept of natural selection and how certain human

adapta-tions relate to our biological past Later chapters have nine

Evolutionary Medicine insights and shorter evolutionary

remarks in the main body of text Students will find novel

and intriguing ways of looking at such topics as

mito-chondria (p 124), hair (p 204), skeletal anatomy (p 286),

body odors (p 595), the taste for sweets (p 990), the

nephron loop (p 897), lactose intolerance (p 970),

menopause (p 1060), and senescence (p 1114)

Pedagogy

Several features of this book are designed to facilitate the

student’s learning

Learning Objectives

I divide each chapter into typically five or six segments of

just a few pages each, with a list of learning objectives at

the beginning and a list of “Before You Go On” content

review questions at the end of each one This enables

stu-dents to set tangible goals for short study periods and to

assess their progress before moving on

Vocabulary Aids

A&P students must assimilate a large working vocabulary

This is far easier and more meaningful if they can

pro-nounce words correctly and if they understand the roots

that compose them Chapter 1 now has a section, “The

Language of Medicine,” which I hope will help get

stu-dents into the habit of breaking new words into familiar

roots, and help them appreciate the importance of

preci-sion in spelling and word use Pronunciation guides are

given parenthetically when new words are introduced,

using a “pro-NUN-see-AY-shun” format that is easy for

students to interpret New terms are accompanied by

foot-notes that identify their roots and origins, and a lexicon of

about 400 most commonly used roots and affixes appears

in appendix C (p A-7)

Self-Testing Questions

Each chapter has about 75 to 90 self-testing questions in

various formats and three levels of difficulty: recall,

description, and analysis or application The ability to

recall terms and facts is tested by 20 multiple choice and

sentence completion questions in the chapter review The

ability to describe concepts is tested by the “Before You Go

On” questions at the ends of the chapter subdivisions,

totaling about 20 to 30 such questions per chapter The

ability to analyze and apply ideas and to relate concepts in

different chapters to each other is tested by an average of 5

“Think About It” questions at intervals throughout each

chapter, 5 “Testing Your Comprehension” essay questions

at the end of the chapter, 10 “True/False” questions in thechapter review that require the student to analyze why thefalse statements are untrue, and usually 5 questions perchapter in the figure legends, prompting the student to ana-lyze or extrapolate from information in the illustrations Agreat number and variety of additional questions are avail-able to students at the Online Learning Center

System Interrelationships

Most instructors would probably agree on the need toemphasize the interrelationships among organ systemsand to discourage the idea that a system can be put out ofone’s mind after a test is over This book reinforces theinterdependence of the organ systems in three ways

1 Beginning with chapter 3 (p 93), each chapter has

a “Brushing Up” box that lists concepts fromearlier chapters that one should understand beforemoving on This may also be useful to studentswho are returning to college and need to freshen

up concepts studied years before, and toinstructors who teach the systems in a differentorder than the book does It also reinforces thecontinuity between A&P I and II

2 For each organ system, there is a “ConnectiveIssues” feature (p 212, for example) thatsummarizes ways in which that system influencesall of the others of the body, and how it is

influenced by them in turn

3 Chapter 29 includes a section, “Senescence of theOrgan Systems,” which can serve as a “capstonelesson” that compellingly shows how the age-related degeneration of each system influences, and

is influenced by, the others Senescence is anincreasingly important topic for health-careproviders as the population increases in averageage This section should sensitize readers not only

to the issues of gerontology, but also to measuresthey can take at a young age to ensure a betterquality of life later on For instructors who prefer totreat senescence of each organ system separatelythroughout the course, earlier chapters cite therelevant pages of this senescence discussion

What’s New?

I’ve been cautious about reorganizing the book and pering with a structure that has been responsible for itssuccess Nevertheless, the voices of many reviewers haveconvinced me that a few changes were in order

tam-Changes in Chapter Sequence

I made two changes in chapter sequencing and numbering:

Nervous System Chapters

The most frequent request has been to give the autonomic

nervous system a chapter of its own, with slightly deeper

coverage I have done so at chapter 15 Another common

request I’ve accommodated has been to discuss the spinal

cord and spinal nerves together in one chapter (now

chap-ter 13) and the brain and cranial nerves together in another

(now chapter 14)

Chemistry

To compensate for the added nervous system chapter

with-out making the book longer, and because many reviewers

felt that the book could do without two full chapters of

chemistry, I condensed the coverage of chemistry by about

25% and combined the two former chemistry chapters into

one (now chapter 2) This results in a change of chapter

numbers from 3 through 15, but from chapter 16 to the end,

the numbers are the same as in the previous editions

Changes in Chapter Organization

In three cases, I felt that a subject could be presented more

effectively by rearrangements and content substitutions

within a chapter Other chapters continue to be organized

as they were in the second edition

Chapter 1, Major Themes of Anatomy

and Physiology

Here I replaced the section on human taxonomic

classifi-cation with sections on anatomical and physiological

variability This gives the chapter a less zoological and

more clinical flavor Also, I feel it is important at the

out-set of such a course to instill a sense of the familiar roots

of biomedical terms, the importance of precision in

spelling, and other aspects of vocabulary Thus I moved

the former appendix B, which introduced students to

medical etymology, to chapter 1 (“The Language of

Med-icine,” p 19)

Chapter 17, The Endocrine System

As many reviewers desired, I have separated endocrine

pathology from normal physiology and placed the

pathol-ogy at the end of the chapter

Chapter 21, The Lymphatic and

Immune Systems

I have found it more effective to present cellular immunity

before humoral immunity, since humoral immunity

depends on some concepts such as helper T cells usually

introduced in the context of cellular immunity

Content Changes

I have strengthened the coverage of the following topics(indicating chapter numbers in parentheses): mitochon-drial diseases (3), autoimmune diseases (5), the stages ofhair growth (6), biomechanics of bone tissue (7), the entericnervous system (15), receptive fields of sensory neurons(16), hormone-transport proteins (17), the blood-thymusbarrier (21), clonal deletion and anergy (21), renal autoreg-ulation (23), lipostats and leptin (26), and the trisomies (29)

I have updated information on the following, drawing

on research and review literature as recent as April 2002,even as the book was in production: genetic translation inthe nucleus (4), signal peptides (4), stem cell research (5),hair analysis (6), osteoporosis treatments (7), knee surgery(9), muscle–connective tissue relationships (11), mitosis incardiac muscle (11), astrocyte functions (12), surgical treat-ment of parkinsonism (12), amyotrophic lateral sclerosis(13), memory consolidation (14), functional MRI (14), thesensory role of filiform papillae (16), a new class of retinalphotoreceptors (16), the history of anesthesia (16), the rela-tionship of growth hormone to somatomedins (17), cyto-toxic T cell activation (21), asthma (21), neuroimmunology(21), atrial natriuretic peptide (23), hunger and bodyweight homeostasis (26), heritability of alcoholism (26),the functions of relaxin (28), contraceptive options (28),the fate of sperm mitochondria (29), Werner syndrome (29),telomeres (29), and theories of aging (29)

Issues of Terminology

In 1999, the Terminologia Anatomica (TA) replaced the

Nomina Anatomica as the international standard for

anatomical terminology I have updated the terminology

in this edition accordingly, except in cases where TA minology is, as yet, so unfamiliar that it may be more ahindrance than a help for an introductory anatomy course

ter-For example, I use the unofficial femur rather than the cial os femoris or femoral bone.

offi-The TA no longer recognizes eponyms, and I haveavoided using them when possible and practical (using

tactile disc instead of Merkel disc, for example) I do

intro-duce common eponyms parenthetically when a term isfirst used Some eponyms are, of course, unavoidable

(Alzheimer disease, Golgi complex) and in some cases it

still seems preferable to use the eponyms because of iarity and correlation with other sources that students will

famil-read (for example, Schwann cell rather than

neurilemmo-cyte).

I follow the recommendation of the American

Med-ical Association Manual of Style (ninth edition, 1998) to

delete the possessive forms of nearly all eponyms There

are people who take offense at the possessive form Down’s

syndrome and yet may be equally insistent that Alzheimer’s disease be in the possessive The AMA has

grappled with such inconsistencies for years, and I accept

its recommendation that the possessives be dropped

whenever possible I make exception for a few cases such

as Broca’s area (which would be awkward to pronounce

without the ’s) and I retain the possessive form for natural

laws (Boyle’s law).

Pedagogic Changes

I have made the following changes in pedagogy; see the

referenced pages for examples of each:

• Added icons to the histological illustrations in chapter

5 to show a place where each tissue can be found

(pp 162–163)

• Added thought questions to some figure legends

(usually five per chapter) and provided answers to

these at the end of the chapter (p 91)

Suggestions Still Welcome!

Many features of this book, and many refinements in thewriting, illustrations, and factual content, came aboutbecause of suggestions and questions from instructors andtheir students In addition, many things that were triedexperimentally in the first edition have been retained inthe later editions because of positive feedback from users.But perfection in textbook writing seems to be an asymp-tote, ever approached but never fully reached I invite mycolleagues and students everywhere to continue offeringsuch valuable and stimulating feedback as I continue theapproach

Ken SaladinDept of BiologyGeorgia College & State UniversityMilledgeville, Georgia 31061 (USA)478-445-0816

ksaladin@gcsu.edu

Teaching and Learning Supplements

McGraw-Hill offers various tools and technology

prod-ucts to support the third edition of Anatomy &

Physiol-ogy Students can order supplemental study materials by

contacting their local bookstore Instructors can obtainteaching aids by calling the Customer Service Depart-ment, at 800-338-3987, visiting our A&P website atwww.mhhe.com/ap, or contacting their local McGraw-Hill sales representative

For the Instructor:

Instructor’s Presentation CD-ROM

This multimedia collection of visual resources allowsinstructors to utilize artwork from the text in multiple for-mats to create customized classroom presentations, visu-ally based tests and quizzes, dynamic course website con-tent, or attractive printed support materials The digitalassets on this cross-platform CD-ROM are grouped bychapter within the following easy-to-use folders

Art Library Full-color digital files of all

illustrations in the book, plus the same art saved inunlabeled and gray scale versions, can be readilyincorporated into lecture presentations, exams, orcustom-made classroom materials These images arealso pre-inserted into blank PowerPoint slides forease of use

Photo Library Digital files of instructionally

significant photographs from the text—including

• For each organ system, added a table of pathologies

which briefly describes several of the most common

dysfunctions and cites pages where other dysfunctions

of that system are mentioned elsewhere in the book

(p 208)

• Changed the chapter reviews from an outline to a

narrative format that briefly restates the key points of

the chapter (p 125)

• Shortened the end-of-chapter vocabulary lists, which

no longer list all boldfaced terms in a chapter, but only

those terms that I deemed most important (p 126)

• Added 10 true/false questions to each chapter review,

with a prompt to explain why the false questions are

untrue (p 127) The answers to these are in appendix

B (p A-2)

Na+ 145 mEq/L K+ 4 mEq/L

K+ 155 mEq/L Na+ 12 mEq/L

Large anions that cannot escape cell ECF

ICF

Figure 12.9 Ionic Basis of the Resting Membrane Potential.

Note that sodium ions are much more concentrated in the extracellular

fluid (ECF) than in the intracellular fluid (ICF), while potassium ions are

more concentrated in the ICF Large anions unable to penetrate the plasma

membrane give the cytoplasm a negative charge relative to the ECF.

If we suddenly increased the concentration of Clⴚions in the

ICF, would the membrane potential become higher or lower

than the RMP?

cadaver, bone, histology, and surface anatomy

images—can be reproduced for multiple

classroom uses

PowerPoint Lecture Outlines Ready-made

presentations that combine art and lecture notes are

provided for each of the 29 chapters of the text

Written by Sharon Simpson, Broward Community

College, these lectures can be used as they are, or

can be tailored to reflect your preferred lecture

topics and sequences

Table Library Every table that appears in the text is

provided in electronic form

In addition to the content found within each chapter, the

Instructor’s Presentation CD-ROM for Anatomy & Physiology

contains the following multimedia instructional materials:

Active Art Library Active Art consists of art files

from key figures from the book that have been

converted to a format that allows the artwork to be

edited inside of Microsoft PowerPoint Each piece of

art inside an Active Art presentation can be broken

down to its core elements, grouped or ungrouped,

and edited to create customized illustrations

Animations Library Numerous full-color

animations illustrating physiological processes are

provided Harness the visual impact of processes in

motion by importing these files into classroom

presentations or online course materials

customized exams This user-friendly program allowsinstructors to search for questions by topic, format, or dif-ficulty level; edit existing questions or add new ones; andscramble questions and answer keys for multiple versions

of the same test Although few textbook authors write theirown test banks, this test bank, written by the author him-self better reflects the textbook than one contracted out to

an independent writer

Other assets on the Instructor’s Testing and ResourceCD-ROM are grouped within easy-to-use folders TheInstructor’s Manual and the Instructor’s Manual to accom-pany the Laboratory Manual are available in both Wordand PDF formats Word files of the test bank are includedfor those instructors who prefer to work outside of the test-generator software

Laboratory Manual

The Anatomy & Physiology Laboratory Manual by Eric

Wise of Santa Barbara City College is expressly written to

coincide with the chapters of Anatomy & Physiology This

lab manual has been revised to include clearer explanations

of physiology experiments and computer simulations thatserve as alternatives to frog experimentation Otherimprovements include a greatly expanded set of reviewquestions at the end of each lab, plus numerous new pho-tographs and artwork

Transparencies

This exhaustive set of over 1,000 transparency overheadsincludes every piece of line art in the textbook, tables, andseveral key photographs An additional set of 150 unla-beled line art duplicates is also available for testing pur-poses or custom labeling Images are printed with bettervisibility and contrast than ever before, and labels arelarge and bold for clear projection

English/Spanish Glossary for Anatomy and Physiology

This complete glossary includes every key term used in atypical 2-semester anatomy and physiology course Defin-itions are provided in both English and Spanish A pho-netic guide to pronunciation follows each word in theglossary

A Visual Atlas for Anatomy and Physiology

This visual atlas contains key gross anatomy illustrationsthat have been blown up in size to make it easier for stu-dents to learn anatomy

Instructor’s Testing and

Resource CD-ROM

This cross-platform CD-ROM provides a wealth of

resources for the instructor Supplements featured on this

CD-ROM include a computerized test bank utilizing

Brownstone Dipoma@ testing software to quickly create

Clinical Applications Manual

Expands on Anatomy and Physiology’s clinical themes,

introduces new clinical topics, and provides test

ques-tions and case studies to develop the student’s ability to

apply his or her knowledge to realistic situations

Course Delivery Systems

With help from our partners, WebCT, Blackboard,

Top-Class, eCollege, and other course management systems,

professors can take complete control over their course

content These course cartridges also provide online

test-ing and powerful student tracktest-ing features The Saladin

Online Learning Center is available within all of these

platforms!

For the Student:

MediaPhys CD-ROM

This interactive tool 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

MediaPhys is filled with interactive activities and quizzes

to help reinforce physiology concepts that are often

on areas where it will be most effective GradeSummit alsoenables instructors to measure their students’ progressand assess that progress relative to others in their classesand worldwide

Online Learning Center

The Anatomy & Physiology Online Learning Center (OLC)

at www.mhhe.com/saladin3 offers access to a vast array of

premium online content to fortify the learning and

teach-ing experience

Essential Study Partner A collection of interactive

study modules that contains hundreds of

animations, learning activities, and quizzes

designed to help students grasp complex concepts

Live News Feeds The OLC offers course specific

real-time news articles to help you stay current with

the latest topics in anatomy and physiology

Student Study Guide

This comprehensive study guide written by JacqueHoman, South Plains College, in collaboration with KenSaladin, contains vocabulary-building and content-testingexercises, labeling exercises, and practice exams

Acknowledgments

A textbook and supplements package on this scale is theproduct of a well coordinated effort by many dedicatedpeople I am deeply indebted to the team at McGraw-HillHigher Education who have shown continued faith in thisbook and invested so generously in it

For their unfailing encouragement and material port, I thank Vice President and Editor-in-Chief MichaelLange and Publisher Marty Lange My appreciation like-wise goes out to Michelle Watnick for her years of ener-getic promotion of the book and lately her role as Spon-soring Editor, and to the legion of sales managers and salesrepresentatives who work so hard to get the book into thehands of my fellow instructors and their students.Kristine Tibbetts, Director of Development, has been

sup-a wonderful editor with whom I’ve been very fortunsup-ate to

work for the past decade The appearance of this book

owes a great deal to Kris’s attention to detail and her

uncompromising commitment to quality, accuracy, and

esthetics Were it not for e-mail, our voluminous

corre-spondence would have required the razing of entire forests

and probably would have detectably enhanced

employ-ment statistics for lumberjacks and postal carriers

Work-ing closely with Kris and me, Designer K Wayne Harms

also deserves a great deal of credit for the esthetic appeal

and readability of these pages

Mary E Powers, Senior Project Manager, has been

responsible for monitoring all aspects of the project, keeping

me and its many other contributors coordinated and moving

toward the book’s timely release She, too, has been a very

alert reader of the entire manuscript and has spared no effort

to incorporate last-minute corrections and to change page

layouts for better figure placement and flow of text

A good copyeditor makes one a better writer, and I

have learned a great deal from my copyeditors on all

edi-tions of this book On this edition, it was Cathy Conroy’s

assiduous attention to detail, ranging from consistency in

anatomical synonyms down to the humblest punctuation

mark, that spared me from committing numerous

embar-rassing errors and inconsistencies

And always high on my list at McGraw-Hill, I am

especially grateful to Colin Wheatley for his conviction,

over a decade ago, that I had a book in me, and for

per-suading me to give it a go Few people have changed my

life so profoundly

The line art in this edition was beautifully executed

by the medical illustrators and graphic artists of

Imagi-neering STA Media Services in Toronto, under the

watch-ful and knowledgeable eye of Jack Haley, Content/Art

Director Imagineering illustrator Dustin Holmes

pro-duced the award-winning cover art for the previous

edi-tion and, not surprisingly, I was delighted with his

execu-tion of the new cover art for this ediexecu-tion For the visual

appeal of this book, credit is also due to McGraw-Hill

Photo Coordinator John Leland and Photo Researcher

Mary T Reeg, who worked hard to acquire photographs

that are clear, informative, and esthetically appealing I

must also repeat my earlier thanks to anatomists Don

Kin-caid and Rebecca Gray of the Ohio State University

Department of Anatomy and Medical Education Morgue

for producing at my behest such clean, instructive

dissec-tions and clear cadaver photographs

For photographs of living subjects, whenever ble I employed volunteers from among my own students

possi-at Georgia College and Stpossi-ate University For kindly ing their bodies to the service of science, I thank my stu-dents, colleagues, friends, and family members: LauraAmmons, Sharesia Bell, Elizabeth Brown, Amy Burmeis-ter, Mae Carpenter, Valeria Champion, Kelli Costa, AdamFraley, Yashica Marshall, Diane Saladin, Emory Saladin,Nicole Saladin, Dilanka Seimon, Natalie Spires, XiaodanWang, Nathan Williams, and Danielle Wychoff Theimproved photographs of joint movements in this edition(chapter 9), with their multiple-exposure effects, are byMilledgeville photographer Tim Vacula

lend-Thanks once again to my colleagues David Evans andEric Wise for their fine work in producing the Instructor’sManual and Laboratory Manual, respectively New thanks toLeslie Miller, M S N., for reviewing the manuscript from aclinical perspective and offering many helpful suggestions.The factual content and accuracy of this edition owe

a great deal to colleagues who are more knowledgeablethan I in specific areas of human anatomy and physiology,and to both colleagues and inquisitive students whosee-mails and other queries sent me to the library to dig stilldeeper into the literature I have gained especially fromthe lively and fruitful discussions on HAPP-L, the e-maillist of the Human Anatomy and Physiology Society(http://www.hapsweb.org); my heartfelt thanks go to themany colleagues who have made HAPP-L such a stimulat-ing and informative site, and to Jim Pendley for maintain-ing the list

Once again, and first in my appreciation, I thank mywife Diane, my son Emory, and my daughter Nicole, not onlyfor sharing with me in the rewards of writing, but also forbearing up so graciously under the demands of having a full-time author cloistered in the inner sanctum of the house

Reviewers

No words could adequately convey my indebtedness andgratitude to the hundreds of A&P instructors and expertswho have reviewed this book in all its editions, and whohave provided such a wealth of scientific information, cor-rections, suggestions for effective presentation, and encour-agement For making the book beautiful, I am indebted to

the team described earlier For making it right, I am

thank-ful to the colleagues listed on the following pages

Reviewers from the United States

Mary Lou Bareither

University of Illinois at Chicago

Julie Harrill Bowers

East Tennessee State University

Redding I Corbett, III

Midlands Technical College

Sarah Caruthers Jackson

Florida Community College–Jacksonville

Robert Moldenhauer

Saint Clair County Community College

David P Sogn Mork

St Cloud State University

Devonna Sue Morra

Saint Francis University

Auburn University Montgomery

Valerie Dean O’Loughlin

Indiana University–

Bloomington

Donald M O’Malley

Northeastern University

Margaret (Betsy) Ott

Tyler Junior College

Avery A Williams

Louisiana State University–Eunice

Bruce Eric Wright

Focus Group Attendees

Reviewers from Canada

Mohawk College of Applied

Arts and Technology

University of Dundee School

of Nursing and Midwifery

Christine Lorraine Carline

Staffordshire University, School

of Health

David Colborn

Independent Consultant, Health

and Social Care

Margaret (Betsy) Ott

Tyler Junior College

Julie C Pilcher

University of Southern Indiana

Linda Powell

Community College of Philadelphia

Margaret (Betsy) Ott

Tyler Junior College

Mattie Roig

Broward Community College

Eva Lurie Weinreb

Community College of Philadelphia

Vernon Lee Wiersema

Houston Community College–Southwest

Saladin’s Anatomy and Physiology brings key

concepts to life with its unique style ofbiomedical illustration.The digitally renderedimages have a vivid three-dimensional lookthat will not only stimulate your students’

interest and enthusiasm, but also give themthe clearest possible understanding ofimportant concepts

Unparalleled Art Program

Saladin’s illustration program includes digitalline art, numerous cadaver photographs, andlight,TEM, and SEM photomicrographs Largerimages and brighter colors in the thirdedition will help draw your students into thesubject

I must say I was completely blown away by this text.The graphics in [a leading text I’ve been using] don’t come close to the graphics in Saladin (which have an extraordinary 3-D quality).

–Bill Schutt, Long Island University

Palmaris longus tendon

Median nerve

Radial artery

Flexor carpi radialis tendon

Flexor pollicis longus tendon

Bursa Flexor retinaculum covering carpal tunnel Trapezium

Superficial palmar arterial arch

Ulnar artery Palmar carpal ligament (cut)

Flexor retinaculum covering carpal tunnel Median nerve

Carpal tunnel Flexor digitorum profundus tendons

Flexor digitorum superficialis tendons

Ulnar bursa

Radial artery

Hamate Trapezium

Scaphoid

Capitate Trapezoid

Thenar muscles

Hypothenar muscles

Ulnar artery

Flexor carpi radialis tendon

Extensor tendons Ventral

Biceps femoris Hamstring group

Semitendinosus Semimembranosus

Adductor magnus Gracilis

Vastus lateralis

Ventral root

Dorsal root

Spinal nerve Dorsal root

ganglion

Sympathetic ganglion Communicating rami Dorsal ramus

Sarcoplasm Sarcolemma

Openings into transverse tubules Sarcoplasmic reticulum Mitochondria

The art program in Saladin’s text is superb Students

today are more “picture oriented” and gain much of

their information from the figures rather than from the

text material The figures in Saladin are clearly and

Calcaneus Plantar fascia (cut)

Abductor hallucis (cut)

Lumbricals

Flexor hallucis longus tendon Flexor digitorum longus tendon

Flexor digitorum brevis (cut)

Flexor hallucis longus tendon (cut) Abductor hallucis (cut)

Plantar view

Dorsal view

Dorsal interosseous

Plantar interosseous

Inner medulla

Outer medulla Cortex

Arcuate vein Arcuate artery

Vasa recta

Ascending limb

Descending limb Nephron loop

Collecting duct

Cortical nephron Juxtamedullary nephron

Glomerular capsule Glomerulus

Proximal convoluted tubule Distal convoluted

Interlobular vein

Interlobular artery

Juxtaglomerular apparatus Renal corpuscle

Peritubular capillaries

Corticomedullary junction Thick

segment Thin segment

M e

l a

C o r t e x

Renal capsule

Collecting duct

Minor calyx

Nephron Renal

Renal medulla

Myelin Motor nerve fiber

Axon terminal Schwann cell Synaptic vesicles (containing ACh)

Basal lamina (containing AChE)

Sarcolemma Region of sarcolemma with ACh receptors

Junctional folds Nucleus of muscle fiber

Aorta

Parietal pleura (cut)

Pulmonary trunk

Parietal pericardium (cut)

Apex

of heart

Diaphragm

Atlas Quality Cadaver Images

Color photographs of cadavers dissected

specifically for this book allow students to

see the real texture of organs and their

relationships to each other.This anatomical

realism combines with the simplified clarity

of line art to give your students a holistic

view of bodily structure

The cadaver photos are excellent! My students (and friends who have taught or taken anatomy class) love them.

–Michael Angilletta, Jr., Indiana State University, Terre Haute

Students have liked the excellent artwork, the charts and tables, and the clinical insights.The photographs

of cadaver dissections and the electron microscopy are excellent.

- Robert Moldenhauer, St Clair County Community College

Accessory nerve (XI) Hypoglossal nerve (XII) Vagus nerve (X)

Oculomotor nerve (III)

Frontal lobe

Olfactory bulb Olfactory tract

Temporal lobe Infundibulum

Medulla

Cerebellum

(a) Optic chiasma

(b)

Longitudinal fissure Frontal lobe

Temporal lobe Pons Medulla oblongata

Spinal cord Cerebellum

Olfactory bulb (from olfactory n., I)

Cranial nerves

Olfactory tract

Optic n (II) Optic chiasma

Trochlear n (IV) Trigeminal n (V) Abducens n (VI) Facial n (VII) Vestibulocochlear

Physiology Focused Art

Saladin illustrates many difficult physiologicalconcepts in steps that students find easy tofollow For students who are "visual learners,"illustrations like these teach more than athousand words

One of the major strengths of the Saladin text, one that

promoted me to adopt the text, was the quality and

quantity of the illustrations In my view, this text is a

hands-down winner in this area.

R Symmons, California State University at Hayward

Erythropoiesis in red bone marrow

Erythrocytes circulate for 120 days

Expired erythrocytes break up in liver and spleen

Small intestine

Cell fragments phagocytized

Globin

Hemoglobin degraded

Hydrolyzed to free amino acids

Heme Iron Biliverdin

Bilirubin Bile Feces

menstruation, injury, etc.

Nutrient absorption

Amino acids Iron Folic acid Vitamin B12

Lymph absorbs

chylomicrons

from small intestine

Lymph drains into bloodstream

Lipoprotein lipase removes lipids from chylomicrons

Liver disposes remnants

Liver produces VLDLs

Leaves LDLs containing mainly cholesterol

Cells requiring cholesterol absorb LDLs

by receptor-mediated endocytosis

Triglycerides are removed and stored in adipocytes

Lipids are stored in

by other cells

Liver produces empty HDL shells

HDL shells pick

up cholesterol and phospholipids from tissues

Filled HDLs return to liver Liver excretes

bile salts

Chylomicron

pathway

VLDL/LDL pathway

HDL pathway

More salt is continually

added by the PCT.

The higher the osmolarity

of the ECF, the more water

leaves the descending limb

by osmosis.

The more water that leaves

the descending limb, the

saltier the fluid is that

remains in the tubule

The more salt that is pumped out of the ascending limb, the saltier the ECF is in the renal medulla.

The saltier the fluid in the salt the tubule pumps into the ECF.

400 600

All life processes are ultimately cellular processes Saladin drives thispoint home with a variety of histological micrographs in LM, SEM, andTEM formats, including many colorized electron micrographs

Photomicrographs Correlated with Line Art

Saladin juxtaposes histological photomicrographswith line art Much like the combination of cadavergross photographs and line art, this gives studentsthe best of both perspectives: the realism of photosand the explanatory clarity of line drawings

From Macroscopic to Microscopic

Saladin’s line art guides students from the intuitive level of gross anatomy

to the functional foundations revealed by microscopic anatomy

The artwork in Saladin is one of its major strengths I applaud this; it really seems to help hold the interest of a wide variety of students.

D Farrington, Russell Sage College

Left pulmonary artery Two lobar arteries

to left lung

Left pulmonary veins Left atrium Left ventricle Right atrium

Right pulmonary veins

Right pulmonary artery Three lobar arteries to right lung

Right ventricle

Pulmonary trunk Aortic arch

Pulmonary vein (to left atrium) Pulmonary artery (from right ventricle) Alveolar sacs and alveoli

(b) (a)

Zone of cell

Zone of cell

Zone of calcification

Zone of bone deposition

Squamous epithelial cells

Nuclei of smooth muscle (b)

Vein Hilum

Medulla

Medullary cord

Medullary sinus Lymphocytes

Venule Trabecula Macrophage

Medullary cords Medullary sinus

Reticular fibers

Efferent lymphatic vessel

Lymphocytes Reticular fibers

(c)

Macrophage

Anatomy and Physiology is fundamentally a

textbook of the basic science of the human

body However, students always want to

know why all the science is relevant to their

career aims Clinical examples and thought

questions make it so Students can see how

the science relates to well-known

dysfunctions, and why it is important to

know the basics Dysfunctions also provide

windows of insight into the basic concepts,

such as the insight that cystic fibrosis gives

on the importance of membrane ion

channels, or that antidepressants give on

the synaptic reuptake of neurotransmitters

Pathology Tables

For each organ system, Saladin presents a

table that briefly describes several

well-known dysfunctions and comprehensively

lists the pages where students can find

comments on other disorders of that

system

There are many tidbits of clinical information

that are in this book, but not in others that I

have seen I think that’s great! I have learned

a thing or two I also think that the author has

tried to choose clinical examples that are

commonly dealt with and therefore most

useful to the student.

L Steele, Ivy Tech State College

order to contract strongly when stimulated Smooth resting length and still contract powerfully There are aments cannot butt against them and stop the contraction;

mus-orderly sarcomeres, stretching of the muscle does not bridges to form; and (3) the thick filaments of smooth

muscle have myosin heads along their entire length (there

just at the ends Smooth muscle also exhibits plasticity—

Thus, a hollow organ such as the bladder can be greatly stretched yet not become flabby when it is empty The muscular system suffers fewer diseases than any other organ system, but several of its more common dys- the muscular system are described on pages 1109–1110.

29 Explain why the stress-relaxation response is an important factor

in smooth muscle function.

436 Part Two Support and Movement

Delayed onset muscle Pain, stiffness, and tenderness felt from several hours to a day after strenuous exercise Associated with microtrauma to

soreness the muscles, with disrupted Z discs, myofibrils, and plasma membranes; and with elevated levels of myoglobin, creatine

kinase, and lactate dehydrogenase in the blood.

Cramps Painful muscle spasms triggered by heavy exercise, extreme cold, dehydration, electrolyte loss, low blood glucose, or lack

of blood flow.

Contracture Abnormal muscle shortening not caused by nervous stimulation Can result from failure of the calcium pump to remove

Ca 2⫹ from the sarcoplasm or from contraction of scar tissue, as in burn patients.

Fibromyalgia Diffuse, chronic muscular pain and tenderness, often associated with sleep disturbances and fatigue; often misdiagnosed

as chronic fatigue syndrome Can be caused by various infectious diseases, physical or emotional trauma, or medications Most common in women 30 to 50 years old.

Crush syndrome A shocklike state following the massive crushing of muscles; associated with high and potentially fatal fever, cardiac

irregularities resulting from K ⫹ released from the muscle, and kidney failure resulting from blockage of the renal tubules with myoglobin released by the traumatized muscle Myoglobinuria (myoglobin in the urine) is a common sign.

Disuse atrophy Reduction in the size of muscle fibers as a result of nerve damage or muscular inactivity, for example in limbs in a cast and

in patients confined to a bed or wheelchair Muscle strength can be lost at a rate of 3% per day of bed rest.

Myositis Muscle inflammation and weakness resulting from infection or autoimmune disease.

Disorders described elsewhere

Athletic injuries p 386 Hernia p 351 Pulled groin p 386 Back injuries p 349 Muscular dystrophy p 437 Pulled hamstrings p 386 Baseball finger p 386 Myasthenia gravis p 437 Rotator cuff injury p 386 Carpal tunnel syndrome p 365 Paralysis p 414 Tennis elbow p 386 Charley horse p 386 Pitcher’s arm p 386 Tennis leg p 386 Compartment syndrome p 386

Chapter 10 The Muscular System351

erection In males, the bulbospongiosus (bulbocavernosus)

semen during ejaculation In females, it encloses the vagina

intercourse Voluntary contractions of this muscle in both

superficial transverse perineus extends from the ischial

tuberosities to a strong central tendon of the perineum.

In the middle compartment, the urogenital triangle is

spanned by a thin triangular sheet called the urogenital

two muscles—the deep transverse perineus and the

exter-contains the external anal sphincter The deepest

com-sexes It consists of two muscle pairs shown in figure

10.20e—the levator ani and coccygeus.

Insight 10.3 Clinical Application

Hernias

A hernia is any condition in which the viscera protrude through a weak

common type to require treatment is an inguinal hernia In the male way of a passage called the inguinal canal through the muscles of the

infants and children When pressure rises in the abdominal cavity, it the scrotum This also sometimes occurs in men who hold their breath cles contract, pressure in the abdominal cavity can soar to 1,500 quite sufficient to produce an inguinal hernia, or “rupture.” Inguinal hernias rarely occur in women.

Longissimus capitis Semispinalis capitis

Superior nuchal line

The accuracy of information in this text is as good as it gets Saladin seems to be right on top of every new bit of information that is revealed What I really like about the Saladin text is that it lets students know when we don’t know why something is the way it is Other texts will try to make the facts fit when they actually don’t.

– W Schmidt, Palm Beach Community College

I like Saladin’s presentation because I feel an understanding of how medicine and science have changed throughout history is part of becoming a "well educated," not just a "well trained" student.

- R Pope, Miami-Dade Community College

All Systems

The respiratory system serves all other systems by supplying O 2 ,

removing CO 2 , and maintaining acid-base balance

Integumentary System

Nasal guard hairs reduce inhalation of dust and other foreign

matter

Skeletal System

Thoracic cage protects lungs; movement of ribs produces pressure

changes that ventilate lungs

Muscular System

Skeletal muscles ventilate lungs, control position of larynx during

swallowing, control vocal cords during speech; exercise strongly

stimulates respiration because of the CO2generated by active

muscles

Nervous System

Produces the respiratory rhythm, monitors blood gases and pH,

monitors stretching of lungs; phrenic, intercostal, and other nerves

control respiratory muscles

Endocrine System

Lungs produce angiotensin-converting enzyme (ACE), which

converts angiotensin I to the hormone angiotensin II

Epinephrine and norepinephrine dilate bronchioles and stimulate

ventilation

Circulatory System

Regulates blood pH; thoracic pump aids in venous return;

lungs produce blood platelets; production of angiotensin II by

lungs is important in control of blood volume and pressure;

obstruction of pulmonary circulation leads to right-sided heart

failure

Blood transports O 2 and CO 2 ; mitral stenosis or left-sided heart

failure can cause pulmonary edema; emboli from peripheral sites

often lodge in lungs

Lymphatic/Immune Systems

Thoracic pump promotes lymph flow

Lymphatic drainage from lungs is important in keeping alveoli dry;

immune cells protect lungs from infection

Urinary System

Valsalva maneuver aids in emptying bladder Disposes of wastes from respiratory organs; collaborates with lungs in controlling blood pH

Digestive System

Valsalva maneuver aids in defecation Provides nutrients for growth and maintenance of respiratory system

Reproductive System

Valsalva maneuver aids in childbirth Sexual arousal stimulates respiration

Interactions Between the RESPIRATORY SYSTEM and Other Organ Systems

indicates ways in which this system affects other systems

indicates ways in which other systems affect this one

of the skin can lead to weakening of the skeleton.For each organ system, a page called ConnectiveIssues shows how it affects other systems of thebody and is affected by them

This section describes the neural mechanisms that regulate pulmonary ventilation Neurons in the medulla scious breathing, whereas neurons in the motor cortex of the cerebrum provide voluntary control.

Control Centers in the Brainstem

The medulla oblongata contains inspiratory (I) neurons,

which fire during forced expiration (but not during cord and synapse with lower motor neurons in the cervi- the phrenic nerves to the diaphragm and intercostal have been found that are analogous to the autorhythmic rhythm of respiration remains unknown despite intensive research.

eup-The medulla has two respiratory nuclei (fig 22.15).

One of them, called the inspiratory center, or dorsal

re-rons, which stimulate the muscles of inspiration The more and the more deeply you inhale If they fire longer than slower When they stop firing, elastic recoil of the lungs and thoracic cage produces passive expiration.

The other nucleus is the expiratory center, or ventral

respiratory group (VRG) It has I neurons in its midregion

involved in eupnea, but its E neurons inhibit the the inspiratory center inhibits the expiratory center when

inspira-an unusually deep inspiration is needed.

The pons regulates ventilation by means of a

pneu-motaxic center in the upper pons and an apneustic

(ap-apneustic center is still unclear, but it seems to prolong sends a continual stream of inhibitory impulses to the quency rises, inspiration lasts as little as 0.5 second and when impulse frequency declines, breathing is slower and deeper, with inspiration lasting as long as 5 seconds.

Think About It

Do you think the fibers from the pneumotaxic center produce EPSPs or IPSPs at their synapses in the inspiratory center? Explain.

858 Part FourRegulation and Maintenance

Pons Medulla

Internal intercostal muscles External intercostal muscles

+Excitation Inhibition

Diaphragm

Figure 22.15 Respiratory Control Centers Functions of the

apneustic center are hypothetical and its connections are therefore indicated by broken lines As indicated by the plus and minus signs, the apneustic center stimulates the inspiratory center, while the pneumotaxic center inhibits it The inspiratory and expiratory centers inhibit each other.

quency rises, inspiration lasts as little as 0.5 second and

the breathing becomes faster and shallower Conversely,

when impulse frequency declines, breathing is slower and

deeper, with inspiration lasting as long as 5 seconds.

Think About It

Do you think the fibers from the pneumotaxic center

produce EPSPs or IPSPs at their synapses in the

inspiratory center? Explain.

The clinical application approach seems much more

consistently and richly in evidence in Saladin.

- D Plantz, Mohave Community College

Overview of the Brain 516

• Directional Terms in Neuroanatomy 516

• Major Landmarks of the Brain 516

• Gray and White Matter 516

• Embryonic Development 517

Meninges, Ventricles, Cerebrospinal Fluid, and Blood Supply 519

• Meninges 519

• Ventricles and Cerebrospinal Fluid 521

• Blood Supply and the Brain Barrier System 524

The Hindbrain and Midbrain 524

• The Medulla Oblongata 524

• The Pons and Cerebellum 526

Higher Brain Functions 536

• Brain Waves and Sleep 536

The Cranial Nerves 546

• The Cranial Nerves—An Aid to Memory 547

Chapter Review 558

INSIGHTS

14.1 Clinical Application:

Meningitis 521

14.2 Medical History: The Accidental

Lobotomy of Phineas Gage 538

14.3 Clinical Application: Some Cranial

• Anatomy of the cranium (pp 248–257)

• Glial cells and their functions (pp 450–451)

• Tracts of the spinal cord (pp 486–489)

• Structure of nerves and ganglia (pp 490–492)

515

Saladin structures each chapter around a consistent and

unique framework of pedagogic devices No matter what

the subject matter of a chapter, this enables students to

develop a consistent learning strategy, making Anatomy

and Physiology a superior learning tool

Insights

Each chapter has from three to six special topic Insight

essays on the history behind the science, the evolution

behind human form and function, and especially the

clinical implications of the basic science Insight sidebars

lend the subject deeper meaning, intriguing perspectives,

and career relevance to the student

Brushing Up

A Brushing Up list at the beginning of the chapter ties

chapters together and reminds students that all organ

systems are conceptually related to each other.They

discourage the habit of forgetting about a chapter after

the exam is over Brushing Up lists are also useful to

instructors who present the subject in a different order from

the textbook

Chapter 14The Brain and Cranial Nerves529

enable the eyes to track and fixate on objects, and

central pattern generators—neuronal pools that

produce rhythmic signals to the muscles of

breathing and swallowing.

• Cardiovascular control The reticular formation

includes the cardiac center and vasomotor center of

the medulla oblongata.

• Pain modulation The reticular formation is the origin

of the descending analgesic pathways mentioned in

the earlier description of the reticulospinal tracts.

• Sleep and consciousness The reticular formation has

projections to the cerebral cortex and thalamus that

allow it some control over what sensory signals reach

the cerebrum and come to our conscious attention It

plays a central role in states of consciousness such as

alertness and sleep Injury to the reticular formation

can result in irreversible coma General anesthetics

work by blocking signal transmission through the

reticular formation.

The reticular formation also is involved in

habitua-tion—a process in which the brain learns to ignore

repeti-others In a noisy city, for example, a person can sleep

an alarm clock or a crying baby Reticular formation nuclei

reticular activating system or extrathalamic cortical

mod-ulatory system.

Before You Go On

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

8 Name the visceral functions controlled by nuclei of the medulla.

9 Describe the general functions of the cerebellum.

10 What are some functions of the midbrain nuclei?

11 Describe the reticular formation and list several of its functions.

The Forebrain

Objectives

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

• name the three major components of the diencephalon and describe their locations and functions;

• identify the five lobes of the cerebrum;

• describe the three types of tracts in the cerebral white matter;

• describe the distinctive cell types and histological arrangement of the cerebral cortex; and

• describe the location and functions of the basal nuclei and limbic system.

The forebrain consists of the diencephalon and and is the most rostral part of the brainstem The telen- cephalon develops chiefly into the cerebrum.

telen-Radiations to cerebral cortex

Descending motor Ascending general

sensory fibers

Reticular formation

Visual input

Auditory input

Figure 14.11The Reticular Formation The formation consists of over 100 nuclei scattered through the brainstem region indicated in red.

Arrows represent the breadth of its projections to and from the cerebral cortex and other CNS regions.

Before You Go On

Saladin divides each chapter into short "digestible"

segments of about three to five pages each Each segmentends with a few content review questions, so students canpause to evaluate their understanding of the previous fewpages before going on

Objectives

Each new section of a chapter begins with a list of learningobjectives Students and instructors find this more usefulthan a single list of objectives at the beginning of achapter, where few students ever refer back to them asthey progress with their reading

I really like having the objectives listed prior to each section instead of in the beginning of each chapter In this manner, they are more appropriate for the students and it helps them focus on the issues of importance of that section The "Think About It" questions are especially nice as it makes the students stop and apply what they have read.

- W Bircher, San Juan College

Chapter Review

Briefly restates the key points of the

chapter

Testing Your Recall

Multiple choice and short answer

questions allow students to check

their knowledge

True or False

Saladin’s True or False questions are

more than they appear.They also

require the student to explain why

the false statements are untrue, thus

challenging the student to think

more deeply into the material and to

appreciate and express subtle

points Answers can be found in the

appendix

558 Part ThreeIntegration and Control

Overview of the Brain (p 516)

1 The adult brain weighs 1,450 to 1,600 g It is divided into the

cerebrum, cerebellum, and brainstem.

2 The cerebrum and cerebellum exhibit

folds called gyri separated by grooves called sulci The groove between the

cerebral hemispheres is the

longitudinal fissure.

3 The cerebrum and cerebellum have

gray matter in their surface cortex and deeper nuclei, and white matter

deep to the cortex.

4 Embryonic development of the brain

progresses through neural plate and neural tube stages in the first 4

weeks The anterior neural tube then

forebrain, midbrain, and hindbrain.

hindbrain show further subdivision into two secondary vesicles each.

Meninges, Ventricles, Cerebrospinal Fluid, and Blood Supply (p 519)

1 Like the spinal cord, the brain is surrounded by a dura mater, arachnoid mater, and pia mater The dura mater is divided into two layers,

periosteal and meningeal, which in

some places are separated by a

blood-filled dural sinus In some places, a subdural space also separates the

dura from the arachnoid.

2 The brain has four internal,

interconnected cavities: two lateral ventricles in the cerebral hemispheres, a third ventricle

between the hemispheres, and a

fourth ventricle between the pons and

The CSF of the ventricles flows from the lateral to the third and then

fourth ventricle, out through foramina in the fourth, into the subarachnoid space around the brain and spinal cord, and finally returns to the blood by way of arachnoid villi.

protection, and chemical stability for the CNS.

6 The brain has a high demand for glucose and oxygen and thus receives

a copious blood supply.

7 The brain barrier and CSF barrier tightly regulate what

blood-substances can escape the blood and reach the nervous tissue.

The Hindbrain and Midbrain (p 524)

1 The medulla oblongata is the most

caudal part of the brain, just inside the foramen magnum It conducts signals up and down the brainstem and between the brainstem and cerebellum, and contains nuclei involved in vasomotion, respiration, coughing, sneezing, salivation, swallowing, gagging, vomiting, gastrointestinal secretion, sweating, and muscles of tongue and head movement Cranial nerves IX through XII arise from the medulla.

2 The pons is immediately rostral to

the medulla It conducts signals up and down the brainstem and between the brainstem and cerebellum, and contains nuclei involved in sleep, hearing, equilibrium, taste, eye movements, facial expression and sensation, respiration, swallowing, bladder control, and posture Cranial nerve V arises from the pons, and nerves VI through VIII arise between the pons and medulla.

3 The cerebellum is the largest part of

the hindbrain It is composed of two hemispheres joined by a vermis, and

has three pairs of cerebellar peduncles that attach it to the

medulla, pons, and midbrain and carry signals between the brainstem and cerebellum.

4 Histologically, the cerebellum exhibits a fernlike pattern of white

matter called the arbor vitae, deep

the white matter, and unusually large

neurons called Purkinje cells.

5 The cerebellum is concerned with motor coordination and judging the passage of time, and plays less- understood roles in awareness, judgment, memory, and emotion.

6 The midbrain is rostral to the pons It

conducts signals up and down the brainstem and between the brainstem and cerebellum, and contains nuclei involved in motor control, pain, visual attention, and auditory reflexes It gives rise to cranial nerves III and IV.

7 The reticular formation is an

elongated cluster of nuclei extending throughout the brainstem, including some of the nuclei already mentioned It is involved in the control of skeletal muscles, the visual gaze, breathing, swallowing, cardiac and vasomotor control, pain, sleep, consciousness, and sensory awareness.

The Forebrain (p 529)

1 The forebrain consists of the diencephalon and cerebrum.

2 The diencephalon is composed of the

thalamus, hypothalamus, and epithalamus.

3 The thalamus receives sensory input

from the brainstem and first two cranial nerves, integrates sensory data, and relays sensory information

to appropriate areas of the cerebrum.

It is also involved in emotion, memory, arousal, and eye movements.

4 The hypothalamus is inferior to the

thalamus and forms the walls and floor of the third ventricle It is a major homeostatic control center It synthesizes some pituitary hormones and controls the timing of pituitary secretion, and it has nuclei concerned with heart rate, blood pressure, gastrointestinal secretion and motility, pupillary diameter,

Chapter Review Review of Key Concepts

440 Part TwoSupport and Movement

Testing Your Recall

1 To make a muscle contract more strongly, the nervous system can activate more motor units This process is called

a the stress-relaxation response

b the length-tension relationship

c excitatory junction potentials

12 A state of prolonged maximum contraction is called

13 Parts of the sarcoplasmic reticulum called lie on each side of a T tubule.

14 Thick myofilaments consist mainly of the protein

15 The neurotransmitter that stimulates skeletal muscle is

16 Muscle contains an oxygen-binding pigment called

17 The of skeletal muscle play the same role as dense bodies in smooth muscle.

18 In autonomic nerve fibers that stimulate single-unit smooth muscle, the neurotransmitter is contained in swellings called

19 A state of continual partial muscle contraction is called

20 is an end product of anaerobic fermentation that causes muscle fatigue.

1 More people get rheumatoid arthritis than osteoarthritis.

2 A doctor who treats arthritis is called

6 The anterior cruciate ligament normally prevents hyperextension of the knee.

7 The femur is held tightly in the acetabulum mainly by the round ligament.

8 The knuckles are diarthroses.

9 Synovial fluid is secreted by the bursae.

10 Unlike most ligaments, the periodontal ligaments do not attach one bone to another.

Testing Your Comprehension

1 All second-class levers produce a mechanical advantage greater than 1.0 and all third-class levers produce

a mechanical advantage less than 1.0.

lever produce more force, or less, than

the force exerted on it? (c) Which of the three classes of levers could not

3 In order of occurrence, list the joint actions (flexion, pronation, etc.) and the joints where they would occur as

you (a) sit down at a table, (b) reach out and pick up an apple, (c) take a bite, and (d) chew it Assume that

you start in anatomical position.

4 Suppose you were dissecting a cat or fetal pig with the task of finding examples of each type of synovial joint Which type of human synovial

joint would not be found in either of those animals? For lack of that joint, what human joint actions would those animals be unable to perform?

5 List the six types of synovial joints and for each one, if possible, identify a joint in the upper limb

falls into each category Which of these six joints have no examples in the lower limb?

Answers at the Online Learning Center

Answers to Figure Legend Questions

9.5 The pubic symphysis consists of the cartilaginous interpubic disc and the adjacent parts of the two pubic bones.

9.6 Interphalangeal joints are not subjected to a great deal of compression.

9.15 MA ⫽ 1.0 Shifting the fulcrum to the left would increase the MA of this lever, while the lever would remain first-class.

9.18 The stylomandibular ligament is relatively remote from the point

where the mandible and temporal bone meet.

9.24 It is the vertical band of tissue immediately to the right of the medial meniscus.

http://www.mhhe.com/saladin3

The Online Learning Center provides a wealth of information fully organized and integrated by chapter You will find practice quizzes, and physiology.

Answers in Appendix B

The "Testing Your Recall" questions

and the "Testing Your Comprehension"

questions provide and excellent

opportunity for students to review the

material in the chapter as a whole,

testing not only recall of information,

but also the student’s ability to apply

the information they recall.

- S Kirkpatrick, Saint Francis University

Testing Your Comprehension

Questions that go beyond memorization to

require a deeper level of analysis and clinical

application Scenarios from Morbidity and

Mortality Weekly Reports and other sources

prompt students to apply the chapter’s basic

science to real-life case histories

Website Reminder

Located at the end of the Chapter Review is areminder that additional study questions andother learning activities for anatomy andphysiology appear on the Online LearningCenter

Answers to Figure Legend Questions

Thought questions have been added to around

five figures per chapter Answers to these

questions are found in this section

The Scope of Anatomy and Physiology 2

• Anatomy—The Study of Form 2

• Physiology—The Study of Function 3

The Origins of Biomedical Science 3

• The Beginnings of Medicine 3

• The Birth of Modern Medicine 3

• Living in a Revolution 6

Scientific Method 7

• The Inductive Method 7

• The Hypothetico-Deductive Method 7

• Experimental Design 7

• Peer Review 8

• Facts, Laws, and Theories 8

Human Origins and Adaptations 9

• Evolution, Selection, and Adaptation 9

• Homeostasis and Negative Feedback 17

• Positive Feedback and Rapid Change 18

The Language of Medicine 19

• The History of Anatomical Terminology 19

• Analyzing Medical Terms 20

• Singular and Plural Forms 21

• The Importance of Precision 21

Review of Major Themes 21 Chapter Review 25

INSIGHTS1.1 Evolutionary Medicine: Vestiges

of Human Evolution 10

1.2 Clinical Application: Situs

Inversus and Other UnusualAnatomy 14

1.3 Medical History: Men in the

Anatomy and Physiology

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

CHAPTER OUTLINE

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

hap-pening and what we can do about it Even the most ancient

writ-ings 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

thou-sands of scientific publications every week

This book is an introduction to human structure and

func-tion, the biology of the human body It is meant primarily to give

you a foundation for advanced study in health care, exercise

phys-iology, 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 a knowledge of it requires us to

com-prehend 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, and a central

concept of physiology called homeostasis.

The Preface to Students describes some ways in which this

book and its companion materials can be used to learn this subject

most effectively If you haven’t already read it, I urge you to do so

before continuing

The Scope of Anatomy

and Physiology

Anatomy is the study of structure, and physiology is the

study of function These approaches are complementary

and never entirely separable When we study a structure,

we want to know, What does it do? Physiology 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

The simplest way to study human anatomy is the

observa-tion of surface structure, for example in performing a

physical examination or making a clinical diagnosis from

surface appearance But a deeper understanding of the

body depends on dissection—the careful cutting and

sep-aration of tissues to reveal their relationships Both

anatomy1and dissection2literally mean “cutting apart”;dissecting used to be called “anatomizing.” The dissection

of a dead human body, or cadaver,3is an essential part ofthe training of many health science students (fig 1.1).Many insights into human structure are obtained from

comparative anatomy—the study of more than one

species in order to learn generalizations and evolutionarytrends Students of anatomy often begin by dissectingother animals with which we share a common ancestryand many structural similarities

Dissection, of course, is not the method of choicewhen studying a living person! Physical examinationsinvolve not only looking at the body for signs of nor-malcy or disease but also touching and listening to it

as palpating a swollen lymph node or taking a pulse

natural sounds made by the body, such as heart and lung

sounds In percussion, the examiner taps on the body

and listens to the sound for signs of abnormalities such

as pockets of fluid or air

Structure that can be seen with the naked eye,whether by surface observation or dissection, is called

gross anatomy Ultimately, though, the functions of the

body result from its individual cells To see those, we ally take tissue specimens, thinly slice and stain them, andobserve them under the microscope This approach is

usu-Figure 1.1 Early Medical Students in the Gross Anatomy Laboratory with Three Cadavers Students of the health sciences

have long begun their professional training by dissecting cadavers

called histology6(microscopic anatomy) Histopathology

is the microscopic examination of tissues for signs of

dis-ease Ultrastructure refers to fine details, down to the

molecular level, revealed by the electron microscope

Physiology—The Study of Function

Physiology7uses the methods of experimental science

dis-cussed later It has many subdisciplines such as

neuro-physiology (physiology of the nervous system),

endocrinology (physiology of hormones), and

pathophys-iology (mechanisms of disease) Partly because of

limita-tions on experimentation with humans, much of what we

know about bodily function has been gained through

com-parative physiology, the study of how different species

have solved problems of life such as water balance,

respi-ration, and reproduction Comparative physiology is also

the basis for the development of new drugs and medical

procedures For example, a cardiac surgeon cannot

prac-tice on humans without first succeeding in animal surgery,

and a vaccine cannot be used on human subjects until it

has been demonstrated through animal research that it

confers significant benefits without unacceptable risks

The Origins of

Biomedical Science

Objectives

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

• give examples of how modern biomedical science emerged

from an era of superstition and authoritarianism; and

• describe the contributions of some key people who helped to

bring about this transformation

Health science has progressed far more in the last 25 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 understanding 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

The Beginnings of Medicine

As early as 3,000 years ago, physicians in Mesopotamia

and Egypt treated patients with herbal drugs, salts,

physi-cal therapy, and faith healing The “father of medicine,”

however, is usually considered to be the Greek physician

Hippocrates (c 460–c 375 B.C.E.) He and his followersestablished a code of ethics for physicians, the Hippo-cratic Oath, that is still recited in modern form by manygraduating medical students Hippocrates urged physi-cians to stop attributing disease to the activities of godsand demons and to seek their natural causes, which could

afford the only rational basis for therapy Aristotle

(384–322B.C.E.) believed that diseases and other naturalevents could have either supernatural causes, which he

called theologi, or natural ones, which he called physici or

physiologi We derive such terms as physician and ology from the latter Until the nineteenth century, physi-

physi-cians were called “doctors of physic.” In his anatomy

book, Of the Parts of Animals, Aristotle tried to identify

unifying themes in nature Among other points, he arguedthat complex structures are built from a smaller variety ofsimple components—a perspective that we will find use-ful later in this chapter

Think About It

When you have completed this chapter, discuss therelevance of Aristotle’s philosophy to our currentthinking about human structure

Claudius Galen (129–c 199), physician to the Roman

gladiators, wrote the most noteworthy medical textbook ofthe ancient era—a book that was worshiped to excess bymedical professors for centuries to follow Cadaver dissec-tion was banned in Galen’s time because of some horridexcesses that preceded him, including dissection of livingslaves and prisoners merely to satisfy an anatomist’scuriosity or to give a public demonstration Galen was lim-ited to learning anatomy from what he observed in treat-ing gladiators’ wounds and by dissecting pigs, monkeys,and other animals Galen saw science as a process of dis-covery, not as a body of fact to be taken on faith He warnedthat even his own books could be wrong, and advised hisfollowers to trust their own observations more than theytrusted any book Unfortunately, his advice was notheeded For nearly 1,500 years, medical professors dog-matically taught what they read in Aristotle and Galen,and few dared to question the authority of these “ancientmasters.”

The Birth of Modern Medicine

Medical science advanced very little during the MiddleAges Even though some of the most famous medicalschools of Europe were founded during this era, the pro-fessors taught medicine primarily as a dogmatic commen-tary on Galen and Aristotle, not as a field of originalresearch Medieval medical illustrations were crude rep-resentations of the body that served more to decorate apage than to depict the body realistically (fig 1.2) Somewere astrological charts that showed which sign of the

zodiac was thought to influence each organ of the body

From such pseudoscience came the word influenza,

Ital-ian for influence.

Free inquiry was less inhibited in the Muslim world

than in Christendom Ibn Sina (980–1037), known in the

West as Avicenna or “the Galen of Islam,” studied Galen

and Aristotle, combined their findings with original

dis-coveries, and questioned authority when the evidence

demanded it Muslim medicine soon became superior to

Western medicine, and Avicenna’s textbook, The Canon of

Medicine, became the leading authority in European

med-ical schools until the sixteenth century

Modern medicine began around the sixteenth

cen-tury in the innovative minds of such people as the

anatomist Andreas Vesalius and the physiologist William

Harvey Andreas Vesalius (1514–64) taught anatomy in

Italy In his time, cadaver dissection had resumed for the

purpose of autopsies and gradually found its way into thetraining of medical students throughout Europe Dissec-tion was an unpleasant business, however, and most pro-fessors considered it beneath their dignity In these daysbefore refrigeration or embalming, the odor from thedecaying cadaver was unbearable Dissections were con-ducted outdoors in a nonstop 4-day race against decay.Bleary medical students had to fight the urge to vomit, lestthey incur the wrath of an overbearing professor Profes-sors typically sat in an elevated chair, the cathedra, read-ing dryly 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 ing and surgery were considered to be “kindred arts of theknife”; today’s barber poles date from this era, their redand white stripes symbolizing blood and bandages.Vesalius broke with tradition by coming down fromthe cathedra and doing the dissections himself He wasquick to point out that much of the anatomy in Galen’sbooks was wrong, and he was the first to publish accurateillustrations for teaching anatomy (fig 1.3) When othersbegan to plagiarize his illustrations, Vesalius published

Barber-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 necessaryfoundation for it What Vesalius was to anatomy, the Eng-

lishman William Harvey (1578–1657) was to physiology.

Harvey is remembered especially for a little book he

pub-lished in 1628, On the Motion of the Heart and Blood in

Animals Authorities before him believed that digested

food traveled to the liver, turned into blood, and then eled through the veins to organs that consumed it Harveymeasured cardiac output in snakes and other animals,however, and concluded that the amount of food eatencould not possibly account for so much blood Thus, heinferred that blood must be recycled—pumped out of theheart by way of arteries and returned to the heart by way

trav-of veins Capillaries, the connections between arteries andveins, had not been discovered yet, but Harvey predictedtheir existence

Modern medicine also owes an enormous debt to two

inventors from this era Antony van Leeuwenhoek

(an-TOE-nee vahn LAY-wen-hook) (1632–1723), a Dutch tile merchant, was the first to invent a microscope capable

tex-of visualizing single cells In order to examine the weave

of fabrics more closely, he ground a beadlike lens andmounted it in a metal plate equipped with a movable spec-

imen clip (fig 1.4) This simple (single-lens) microscope

magnified objects 200 to 300 times Out of curiosity,Leeuwenhoek examined a drop of lake water and wasastonished to find a variety of microorganisms—“littleanimalcules,” he called them, “very prettily a-swimming.”

Figure 1.2 Medieval Medical Illustration This figure depicts a

pregnant woman with a fetus in the uterus and shows the heart, lungs,

arteries, and digestive tract

He went on to observe practically everything he could get

his hands on, including blood cells, blood capillaries,

sperm, and muscular tissue Probably no one in history

had looked at nature in such a revolutionary way

Leeuwenhoek opened the door to an entirely new

under-standing of human structure and the causes of disease He

was praised at first, and reports of his observations were

eagerly received by scientific societies, but this public

enthusiasm did not last By the end of the seventeenth

century, the microscope was treated as a mere toy for the

upper classes, as amusing and meaningless as a

kaleido-scope Leeuwenhoek had even become the brunt of satire

Leeuwenhoek’s most faithful admirer was the

English-man Robert Hooke (1635–1703), who developed the first

practical compound microscope—a tube with a lens at each

end The second lens further magnified the image produced

by the first (fig 1.5a) Hooke invented many of the features

found in microscopes used today: a stage to hold the men, an illuminator, and coarse and fine focus controls Hismicroscopes produced poor images with blurry edges

speci-(spherical aberration) and rainbow-colored distortions (chromatic aberration), but poor images were better than

none Although Leeuwenhoek was the first to see cells,

Figure 1.3 The Art of Vesalius Andreas Vesalius revolutionized

medical illustration with the comparatively realistic art prepared for his

1543 book, De Humani Corporis Fabrica.

Lens Specimen holder

Focusing screw

Handle

(a)

Figure 1.4 Leeuwenhoek’s Simple Microscope (a) Modern

replica (b) Viewing a specimen with a Leeuwenhoek microscope.

(b)

Hooke named them In 1663, he observed thin shavings of

cork with his microscope and observed that they “consisted

of a great many little boxes,” which he called cells after the

cubicles of a monastery (fig 1.5b) He published these

obser-vations in his book, Micrographia, in 1665.

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 that reduced

chromatic and spherical aberration Chapter 3 describes

some more recently invented types of microscopes 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 This was the first tenet of the cell theory, added to by

later biologists and summarized in chapter 3 The cell

the-ory was perhaps the most important breakthrough in

bio-medical history, because all functions of the body are now

interpreted as the effects of cellular activity

Although the philosophical foundation for modern

medicine was largely established by the time of

Leeuwen-hoek, Hooke, and Harvey, clinical practice was still in adismal state Few doctors attended medical school orreceived any formal education in basic science or humananatomy Physicians tended to be ignorant, ineffective,and pompous Their practice was heavily based onexpelling imaginary toxins from the body by bleedingtheir patients or inducing vomiting, sweating, or diarrhea.They performed operations with dirty hands and instru-ments, spreading lethal infections from one patient toanother Fractured limbs often became gangrenous andhad to be amputated, and there was no anesthesia to lessenthe pain Disease was still widely attributed to demonsand witches, and many people felt they would be interfer-ing with God’s will if they tried to treat it

Living in a Revolution

This short history brings us only to the threshold of ern biomedical science; it stops short of such momentousdiscoveries as the germ theory of disease, the mechanisms

mod-of heredity, and the structure mod-of DNA In the twentieth tury, basic biology and biochemistry have given us a muchdeeper understanding of how the body works Technolog-ical advances such as medical imaging (see insight 1.5,

cen-p 22) have enhanced our diagnostic ability and life-supportstrategies We have witnessed monumental developments

in chemotherapy, immunization, anesthesia, surgery,organ transplants, and human genetics By the close of thetwentieth century, we had discovered the chemical “basesequence” of every human gene and begun using genetherapy to treat children born with diseases recently con-sidered incurable As future historians look back on theturn of this century, they may exult about the Genetic Rev-olution in which you are now living

Several discoveries of the nineteenth and twentiethcenturies, and the men and women behind them, are cov-ered in short historical sketches in later chapters Yet, thestories told in this chapter are different in a significantway The people discussed here were pioneers in estab-lishing the scientific way of thinking They helped toreplace superstition with an appreciation of natural law.They bridged the chasm between mystery and medication.Without this intellectual revolution, those who followedcould not have conceived of the right questions to ask,much less a method for answering them

3 How is our concept of human form and function today affected

by inventors from Leeuwenhoek to Zeiss?

Figure 1.5 Hooke’s Compound Microscope (a) The compound

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

Scientific Method

Objectives

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

• describe the inductive and hypothetico-deductive methods of

obtaining scientific knowledge;

• describe some aspects of experimental design that help to

ensure objective and reliable results; and

• 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

general-izations 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 each other, both men wanted science to

become a public, cooperative enterprise, supported by

governments and conducted by an international

commu-nity 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

sci-ence on the path to modernity, not by discovering

any-thing new in nature or inventing any techniques—for

nei-ther man was a scientist—but by inventing new habits of

scientific thought

When we say “scientific,” we mean that such

think-ing is based on assumptions and methods that yield

reli-able, objective, testable information about nature The

assumptions of science are ideas that have proven fruitful

in the past—for example, the idea that natural phenomena

have natural causes and nature is therefore predictable

and understandable The methods of science are highly

variable Scientific method refers less to observational

procedures than to certain habits of disciplined creativity,

careful observation, logical thinking, and honest 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 feelsconfident in drawing generalizations and predictions fromthem What we know of anatomy is a product of the induc-tive method We describe the normal structure of the bodybased on observations of many bodies

This raises the issue of what is considered proof inscience We can never prove a claim beyond all possiblerefutation We can, however, consider a statement as

proven beyond reasonable doubt if it was arrived at by

reliable methods of observation, tested and confirmedrepeatedly, and not falsified by any credible observation

In science, all truth is tentative; there is no room fordogma 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

edu-cated speculation or possible answer to the question Agood hypothesis must be (1) consistent with what isalready 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 specifywhat evidence it would take to prove it wrong If nothingcould possibly prove it wrong, then it is not scientific

Think About It

The ancients thought that gods or invisible demonscaused epilepsy Today, epileptic seizures areattributed to bursts of abnormal electrical activity innerve cells of the brain Explain why one of theseclaims is falsifiable (and thus scientific), while theother claim is not

The purpose of a hypothesis is to suggest a method foranswering a question From the hypothesis, a researchermakes a deduction, typically in the form of an “if-then”

prediction: 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 ducted experiment yields observations that either support

con-a hypothesis or require the scientist to modify or con-abcon-andon

it, formulate a better hypothesis, and test that one esis testing operates in cycles of conjecture and disproofuntil one is found that is supported by the evidence

Hypoth-Experimental Design

Doing an experiment properly involves several tant considerations What shall I measure and how can I

measure 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

sub-jects, 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 conclusions as I do? Several elements of

experi-mental 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

example, would you rather trust your health to a drug

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

• 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, a group of people with high cholesterol

was 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 impact 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

starch 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 subject is

receiving the experimental treatment or placebo Aresearcher might prepare identical-looking tablets,some with the drug and some with placebo, label themwith code numbers, and distribute them to

participating physicians The physicians themselves

do not know whether they are administering drug orplacebo, so they cannot give the subjects evenaccidental hints of which substance they are taking.When the data are collected, the researcher cancorrelate them with the composition of the tablets anddetermine whether the drug had more effect than theplacebo

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

would expect it to come up about 50 heads and 50tails If it actually came up 48:52, you would probablyattribute this to random error rather than bias in thecoin But what if it came up 40:60? At what pointwould you begin to suspect bias? This type of problem

is faced routinely in research—how great a differencemust there be between control and experimentalgroups before we feel confident that the treatmentreally had an effect? What if a treatment groupexhibited a 12% reduction in cholesterol level and theplacebo group a 10% reduction? Would this be enough

to conclude that the treatment was effective?

Scientists are well grounded 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 typical outcome of a statistical testmight be expressed, “We can be 99.5% sure that thedifference between group A and group B was due tothe experimental treatment and not to randomvariation.”

Peer Review

When a scientist applies for funds to support a researchproject 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 ispublished, if the results are important or unconventional,other scientists may attempt to reproduce them to see if theauthor was correct At every stage from planning to post-publication, scientists are therefore subject to intensescrutiny by their colleagues Peer review is one mechanismfor ensuring honesty, objectivity, and quality in science

Facts, Laws, and Theories

The most important product of scientific research isunderstanding how nature works—whether it be thenature 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 between these

A scientific fact is information that can be

independ-ently 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

mat-ter and energy behave It is the result of inductive

reason-ing based on repeated, confirmed observations Some laws

are expressed as concise verbal statements, such as the

first law of thermodynamics: Energy can be converted

from one form to another but cannot be created or

destroyed Others are expressed as mathematical

formu-lae, such as the law of Laplace: F ⫽ 2T/r, where F is a force

that tends to cause a microscopic air sac of the lung to

col-lapse, T is the surface tension of the fluid lining the sac,

and r is the sac’s radius.

A theory is an explanatory statement, or set of

state-ments, derived from facts, laws, and confirmed

hypothe-ses Some theories have names, such as the cell theory,

the fluid-mosaic theory of cell membranes, and the

slid-ing filament theory of muscle contraction Most,

how-ever, remain unnamed The purpose of a theory is not

only to concisely summarize what we already know but,

moreover, to suggest 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

sci-ence 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

description; 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

peo-ple to think that a scientific theory (such as the theory of

evolution) is merely a guess or conjecture, instead of

rec-ognizing 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

Think About It

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:

4 Describe the general process involved in the inductive method

5 Describe some sources of potential bias in biomedical research

What are some ways of minimizing such bias?

6 Is there more information in an individual scientific fact or in a

theory? Explain

Human Origins and Adaptations

Objectives

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

• define evolution and natural selection;

• describe some human characteristics that can be attributed

to the tree-dwelling habits of earlier primates;

• describe some human characteristics that evolved later inconnection with upright walking; and

• explain why evolution is relevant to understanding humanform and function

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

theory and the theory of natural selection Natural

selec-tion, 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 foundly changed the prevailing view of our origin, nature,and place in the universe

pro-On the Origin of Species scarcely touched upon

human biology, but its unmistakable implications forhumans 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 andemphasized features of anatomy and behavior that revealour relationship to other animals No understanding ofhuman 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 theevolution of bacterial resistance to antibiotics, theappearance of new strains of the AIDS virus, and the emer-

gence of new species of organisms The theory of natural

selection is essentially this: Some individuals within a

species have hereditary advantages over their tors—for example, better camouflage, disease resistance,

competi-or ability to attract mates—that enable them to producemore offspring They pass these advantages on to theiroffspring, and such characteristics therefore becomemore and more common in successive generations Thisbrings about the genetic change in a population that con-stitutes evolution

Natural forces that promote the reproductive cess of some individuals more than others are called

suc-selection 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

Darwin could scarcely have predicted the

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

evi-dence 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 us

Several aspects of our anatomy make little sense

without an awareness that the human body has a history

(see insight 1.1) Our evolutionary relationship to other

species is also important in choosing animals for

biomed-ical research If there were no issues of cost, availability, or

ethics, we might test drugs on our nearest 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 reality, we

com-promise Rats and mice are used extensively for research

because they are fellow mammals with a physiology

simi-lar to ours, but they present fewer of the aforementioned

issues than chimpanzees or other mammals do An animal

species or strain selected for research on a particular

prob-lem is called a model—for example, a mouse model for

leukemia

Primate Adaptations

We belong to an order of mammals called the Primates,which also includes the monkeys and apes Some of ouranatomical and physiological features can be traced to theearliest 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 arboreal8

(treetop) habitat probably afforded greater safety from ators, less competition, and a rich food supply of leaves,fruit, insects, and lizards But the forest canopy is a chal-lenging world, with dim and dappled sunlight, swayingbranches, and prey darting about in the dense foliage Anynew feature that enabled arboreal animals to move aboutmore easily in the treetops would have been strongly favored

pred-by natural selection Thus, the shoulder became more mobileand enabled primates to reach out in any direction (evenoverhead, which few other mammals can do) The thumbs

became opposable—they could cross the palm to touch the

fingertips—and enabled primates to hold small objects andmanipulate them more precisely than other mammals can

Opposable thumbs made the hands prehensile9—able tograsp branches by encircling them with the thumb and fin-gers (fig 1.6) The thumb is so important that it receiveshighest priority in the repair of hand injuries If the thumbcan be saved, the hand can be reasonably functional; if it islost, hand functions are severely diminished

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 piloerector muscle In other mammals,

these muscles fluff the hair and conserve heat In humans, they

merely produce goose bumps Above each ear, we have three

auricu-laris muscles In other mammals, they move the ears to receive

sounds better, but most people cannot contract them at all As

Dar-win 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

Monkey

Human

Figure 1.6 Primate Hands The opposable thumb makes the

primate hand prehensile, able to encircle and grasp objects

8

9

The eyes of primates moved to a more forward-facing

position (fig 1.7), which allowed for stereoscopic10vision

(depth perception) This adaptation provided better

hand-eye coordination in catching and manipulating prey, with

the added advantage of making it easier to judge distances

accurately in leaping from tree to tree Color vision, rare

among mammals, is also a primate hallmark Primates eat

mainly fruit and leaves The ability to distinguish subtle

shades of orange and red enables them to distinguish ripe,

sugary fruits from unripe ones Distinguishing subtle

shades of green helps them to differentiate between tender

young leaves and tough, more toxic older foliage

Various fruits ripen at different times and in widely

separated places in the tropical forest This requires a good

memory of what will be available, when, and how to get

there Larger brains may have evolved in response to the

challenge of efficient food finding and, in turn, laid the

foundation for more sophisticated social organization

None of this is meant to imply that humans evolved

from monkeys or apes—a common misconception about

evolution that no biologist believes Observations of

mon-keys and apes, however, provide insight into how

pri-mates adapt to the arboreal habitat and how certain human

adaptations probably originated

Walking Upright

About 4 to 5 million years ago, much of the African forest

was replaced by savanna (grassland) Some primates

adapted to living on the savanna, but this was a dangerous

place with more predators and less protection Just as

squirrels and monkeys stand briefly on their hind legs tolook around for danger, so would these early ground-dwellers Being able to stand up not only helps an animalstay alert but also frees the forelimbs for purposes otherthan walking Chimpanzees sometimes walk upright tocarry food or weapons (sticks and rocks), and it is reason-able to suppose that our early ancestors did so too Theycould also carry their infants

These advantages are so great that they favored

skeletal modifications that made bipedalism11ing and walking on two legs—easier The anatomy of thehuman pelvis, femur, knee, great toe, foot arches, spinalcolumn, skull, arms, and many muscles became adaptedfor bipedal locomotion, as did many aspects of humanfamily life and society As the skeleton and musclesbecame adapted for bipedalism, brain volume increaseddramatically (table 1.1) It must have become increas-ingly difficult for a fully developed, large-brained infant

—stand-to pass through the mother’s pelvic outlet at birth Thismay explain why humans are born in a relatively imma-ture, helpless state compared to other mammals, beforetheir nervous systems have matured and the bones of theskull have fused

The oldest bipedal primates (family Hominidae)

are classified in the genus Australopithecus oh-PITH-eh-cus) About 2.5 million years ago, Australo-

(aus-TRAL-pithecus gave rise to Homo habilis, the earliest member

of our own genus Homo habilis differed from

Australo-pithecus in height, brain volume, some details of skull

anatomy, and tool-making ability It was probably the

first primate able to speak Homo habilis gave rise to

Homo erectus about 1.1 million years ago, which in turn

led to our own species, Homo sapiens, about 300,000 years ago (fig 1.8) Homo sapiens includes the extinct

Neanderthal and Cro-Magnon people as well as modernhumans

This brief account barely begins to explain how humananatomy, physiology, and behavior have been shaped by

Figure 1.7 Primitive Tool Use in a Primate Chimpanzees exhibit

the prehensile hands and forward-facing eyes typical of primates Such

traits endow primates with stereoscopic vision (depth perception) and

good hand-eye coordination, two supremely important factors in human

evolution

10

the Hominidae

ancient selection pressures Later chapters further

demon-strate that the evolutionary perspective provides a

meaning-ful understanding of why humans are the way we are

Evo-lution is the basis for comparative anatomy and physiology,

which have been so fruitful for the understanding of human

biology If we were not related to any other species, those

sci-ences would be pointless The emerging science of

evolu-tionary (darwinian) medicine traces some of our diseases

and imperfections to our evolutionary past

Before You Go On

Answer the following questions to test your understanding of the

preceding section:

7 Define adaptation and selection pressure Why are these

concepts important in understanding human anatomy and

physiology?

8 Select any two human characteristics and explain how they

may have originated in primate adaptations to an arboreal

habitat

9 Select two other human characteristics and explain how they

may have resulted from adaptation to a grassland habitat

Human Structure

Objectives

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

• list the levels of human structure from the most complex tothe simplest;

• discuss the value of both reductionistic and holisticviewpoints to understanding human form and function; and

• discuss the clinical significance of anatomical variationamong humans

Earlier in this chapter, we observed that human anatomy isstudied by a variety of techniques—dissection, palpation,and so forth In addition, anatomy is studied at several levels

of detail, from the whole body down to the molecular level

The Hierarchy of Complexity

Consider for the moment an analogy to human structure:The English language, like the human body, is very com-plex, yet an endless array of ideas can be conveyed with alimited number of words All words in English are, in turn,

Millions of years ago

New World monkeys Old World monkeys Gibbon and orangutan Gorilla

Common chimpanzee Bonobo

Australopithecines (extinct)

Homo

Prosimians

Figure 1.8 The Place of Humans in Primate Evolution Figures at the right show some representative primates The branch points in this

“family tree” show the approximate times that different lines diverged from a common ancestor Note that the time scale is not uniform; recent eventsare expanded for clarity

Which is more closely related to humans, a gorilla or a monkey? How long ago did the last common ancestor of chimpanzees and humans exist?

composed of various combinations of just 26 letters

Between an essay and an alphabet are successively simpler

levels of organization: paragraphs, sentences, words, and

syllables We can say that language exhibits a hierarchy of

complexity, with letters, syllables, words, and so forth

being successive levels of the hierarchy Humans have an

analogous hierarchy of complexity, as follows (fig 1.9):

The organism is composed of organ systems,

organ systems are composed of organs,

organs are composed of tissues,

tissues are composed of cells,

cells are composed (in part) of organelles,

organelles are composed of molecules, and

molecules are composed of atoms

The organism is a single, complete individual.

An organ system is a group of organs with a unique

collective function, such as circulation, respiration, or

digestion The human body has 11 organ systems,

illus-trated in atlas A immediately following this chapter: the

integumentary, skeletal, muscular, nervous, endocrine,

circulatory, lymphatic, respiratory, urinary, digestive, and

reproductive systems Usually, the organs of one systemare physically interconnected, such as the kidneys,ureters, urinary bladder, and urethra, which compose theurinary system Beginning with chapter 6, this book isorganized around the organ systems

An organ is a structure composed of two or more

tis-sue types that work together to carry out a particular tion Organs have definite anatomical boundaries and arevisibly distinguishable from adjacent structures Mostorgans and higher levels of structure are within the domain

func-of gross anatomy However, there are organs within organs—the large organs visible to the naked eye often containsmaller organs visible only with the microscope The skin,for example, is the body’s largest organ Included within itare thousands of smaller organs: each hair, nail, gland,nerve, and blood vessel of the skin is an organ in itself

A tissue is a mass of similar cells and cell products

that forms a discrete region of an organ and performs a cific function The body is composed of only four primaryclasses of tissue—epithelial, connective, nervous, andmuscular tissues Histology, the study of tissues, is thesubject of chapter 5

spe-Cells are the smallest units of an organism that carry

out all the basic functions of life; nothing simpler than a

cell is considered alive A cell is enclosed in a plasma

membrane composed of lipids and proteins Most cells

have one nucleus, an organelle that contains its DNA

Cytology, the study of cells and organelles, is the subject of

chapters 3 and 4

carry out its individual functions Examples include chondria, centrioles, and lysosomes

mito-Organelles and other cellular components are

com-posed of molecules The largest molecules, such as

pro-teins, fats, and DNA, are called macromolecules A

mole-cule is a particle composed of at least two atoms, the

smallest particles with unique chemical identities

The theory that a large, complex system such as thehuman body can be understood by studying its simpler

components is called reductionism First espoused by

Aris-totle, this has proven to be a highly productive approach;indeed, it is essential to scientific thinking Yet the reduc-tionistic view is not the last word in understanding humanlife Just as it would be very difficult to predict the workings

of an automobile transmission merely by looking at a pile ofits disassembled gears and levers, one could never predictthe human personality from a complete knowledge of thecircuitry of the brain or the genetic sequence of DNA

“emer-gent properties” of the whole organism that cannot be dicted from the properties of its separate parts—humanbeings are more than the sum of their parts To be most effec-tive, a health-care provider does not treat merely a disease

Figure 1.9 The Body’s Structural Hierarchy.

12

elle⫽ little 13

holo⫽ whole, entire

or an organ system, but a whole person A patient’s

percep-tions, emotional responses to life, and confidence in the

nurse, therapist, or physician profoundly affect the outcome

of treatment In fact, these psychological factors often play a

greater role in a patient’s recovery than the physical

treat-ments administered

Anatomical Variation

Anatomists, surgeons, and students must be constantly

aware of how much one body can differ from another A

quick look around any classroom is enough to show that

no two humans are exactly alike; on close inspection, even

identical twins exhibit differences Yet anatomy atlases

and textbooks can easily give you the impression that

everyone’s internal anatomy is the same This simply is

not true Books such as this one can only teach you the

most common structure—the anatomy seen in about 70%

or more of people Someone who thinks that all human

bodies are the same internally would make a very

con-fused medical student or an incompetent surgeon

Some people lack certain organs For example, most

of us have a palmaris longus muscle in the forearm and a

plantaris muscle in the lower leg, but these are absent

from some people Most of us have five lumbar vertebrae

(bones of the lower spine), but some people have six and

some have four Most of us have one spleen and two

kid-neys, but some have two spleens or only one kidney Most

kidneys are supplied by a single renal artery, but some

have two renal arteries Figure 1.10 shows some common

variations in human anatomy, and insight 1.2 describes a

particularly dramatic and clinically important variation

Think About It

People who are allergic to aspirin or penicillin oftenwear Medic Alert bracelets or necklaces that note thisfact in case they need emergency medical treatmentand are unable to communicate Why would it beimportant for a person with situs inversus to have thisnoted on a Medic Alert bracelet?

11 How are tissues relevant to the definition of an organ?

12 Why is reductionism a necessary but not sufficient point of viewfor fully understanding a patient’s illness?

13 Why should medical students observe multiple cadavers and not

be satisfied to dissect only one?

Human Function

Objectives

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

• state the characteristics that distinguish living organismsfrom nonliving objects;

• explain the importance of defining a reference man andwoman;

• define homeostasis and explain why this concept is central

to physiology;

• define negative feedback, give an example of it, and explain

its importance to homeostasis; and

• define positive feedback and give examples of its beneficial

and harmful effects

Characteristics of Life

Why do we consider a growing child to be alive, but not

a growing crystal? Is abortion the taking of a human life?

If so, what about a contraceptive foam that kills onlysperm? As a patient is dying, at what point does itbecome ethical to disconnect life-support equipment andremove organs for donation? If these organs are alive, asthey must be to serve someone else, then why isn’t thedonor considered alive? Such questions have no easyanswers, but they demand a concept of what life is—aconcept that may differ with one’s biological, medical, orlegal perspective

From a biological viewpoint, life is not a single erty It is a collection of properties that help to distinguishliving from nonliving things:

prop-• Organization Living things exhibit a far higher level

of organization than the nonliving world around them.They expend a great deal of energy to maintain order,

Situs Inversus and Other Unusual Anatomy

In most people, the spleen, pancreas, sigmoid colon, and most of the heart

are on the left, while the appendix, gallbladder, and most of the liver are

on the right The normal arrangement of these and other internal organs

is called situs (SITE-us) solitus About 1 in 8,000 people, however, are born

with an abnormality called situs inversus—the organs of the thoracic and

abdominal cavities are reversed between right and left A selective

right-left reversal of the heart is called dextrocardia In situs perversus, a

sin-gle organ occupies an atypical position—for example, a kidney located

low in the pelvic cavity instead of high in the abdominal cavity

Conditions such as dextrocardia in the absence of complete situs

inversus can cause serious medical problems Complete situs inversus,

however, usually causes no functional problems because all of the

vis-cera, though reversed, maintain their normal relationships to each

other Situs inversus is often discovered in the fetus by sonography, but

many people remain unaware of their condition for decades until it is

discovered by medical imaging, on physical examination, or in surgery

You can easily imagine the importance of such conditions in

diagnos-ing appendicitis, performdiagnos-ing gallbladder surgery, interpretdiagnos-ing an X ray,

or auscultating the heart valves

Figure 1.10 Variation in Human Anatomy The left-hand figure in each case depicts the most common anatomy (a) Variations in stomach shape

correlated with body physique (b) Variations in the position of the appendix (c) Variations in the bile passages of the liver and gallbladder.

and a breakdown in this order is accompanied by

disease and often death

• Cellular composition Living matter is always

compartmentalized into one or more cells

• Metabolism and excretion Living things take in

molecules from the environment and chemically

change them into molecules that form their own

structures, control their physiology, or provide them

with energy Metabolism14is the sum of all this

internal chemical change It consists of two classes of

reactions: anabolism,15in which relatively complex

molecules are synthesized from simpler ones (for

example, protein synthesis), and catabolism,16in

which relatively complex molecules are broken down

into simpler ones (for example, protein digestion)

Metabolism inevitably produces chemical wastes,

some of which are toxic if they accumulate

Metabolism therefore requires excretion, the

separation of wastes from the tissues and their

elimination from the body There is a constant

turnover of molecules in the body; few of the

molecules now in your body have been there for more

than a year It is food for thought that although you

sense a continuity of personality and experience from

your childhood to the present, nearly all of your body

has been replaced within the past year

• Responsiveness and movement The ability of

organisms to sense and react to stimuli (changes in

their environment) is called responsiveness, irritability,

or excitability It occurs at all levels from the single cell

to the entire body, and it characterizes all living things

from bacteria to you Responsiveness is especially

obvious in animals because of nerve and muscle cells

that exhibit high sensitivity to environmental stimuli,

rapid transmission of information, and quick reactions

Most living organisms are capable of self-propelled

movement from place to place, and all organisms and

cells are at least capable of moving substances

internally, such as moving food along the digestive

tract or moving molecules and organelles from place to

place within a cell

• Homeostasis While the environment around an

organism changes, the organism maintains relatively

stable internal conditions This ability to maintain

internal stability, called homeostasis, is explored in

more depth shortly

• Development Development is any change in form or

function over the lifetime of the organism In most

organisms, it involves two major processes:

(1) differentiation, the transformation of cells with no

specialized function into cells that are committed to a

particular task, and (2) growth, an increase in size.

Some nonliving things grow, but not in the way yourbody does If you let a saturated sugar solutionevaporate, crystals will grow from it, but not through achange in the composition of the sugar They merelyadd more sugar molecules from the solution to thecrystal surface The growth of the body, by contrast,occurs through chemical change (metabolism); for themost part, your body is not composed of the moleculesyou ate but of molecules made by chemically alteringyour food

• Reproduction All living organisms can produce

copies of themselves, thus passing their genes on tonew, younger containers—their offspring

• Evolution All living species exhibit genetic change

from generation to generation and therefore evolve

This occurs because mutations (changes in DNA

structure) are inevitable and because environmentalselection pressures endow some individuals withgreater reproductive success than others Unlike theother characteristics of life, evolution is a

characteristic seen only in the population as awhole No single individual evolves over the course

of its life

Clinical and legal criteria of life differ from these logical criteria A person who has shown no brain wavesfor 24 hours, and has no reflexes, respiration, or heartbeatother than what is provided by artificial life support, can

bio-be declared legally dead At such time, however, most ofthe body is still biologically alive and its organs may beuseful for transplant

Physiological Variation

Earlier we considered the clinical importance of tions in human anatomy, but physiology is even more vari-able Physiological variables differ with sex, age, weight,diet, degree of physical activity, and environment, amongother things Failure to consider such variation leads tomedical mistakes such as overmedication of the elderly ormedicating women on the basis of research that was done

varia-on men If an introductory textbook states a typical humanheart rate, blood pressure, red blood cell count, or bodytemperature, it is generally assumed that such values arefor a healthy young adult unless otherwise stated A point

of reference for such general values is the reference man

and reference woman The reference man is defined as a

healthy male 22 years old, weighing 70 kg (154 lb), living

at a mean ambient (surrounding) temperature of 20⬚C,engaging in light physical activity, and consuming 2,800

kilocalories (kcal) per day The reference woman is the

same except for a weight of 58 kg (128 lb) and an intake of2,000 kcal/day

Homeostasis and Negative Feedback

that will arise most frequently in this book as we study

mechanisms of health and disease The human body has a

remarkable capacity for self-restoration Hippocrates

com-mented that it usually returns to a state of equilibrium by

itself, and people recover from most illnesses even

with-out the help of a physician This tendency results from

homeostasis, the ability to detect change and activate

mechanisms that oppose it

French physiologist Claude Bernard (1813–78)

observed that the internal conditions of the body remain

fairly stable even when external conditions vary greatly

For example, whether it is freezing cold or swelteringly

hot outdoors, the internal temperature of your body stays

within a range of about 36⬚ to 37⬚C (97⬚–99⬚F) American

physiologist Walter Cannon (1871–1945) coined the term

homeostasis for this tendency to maintain internal

stabil-ity Homeostasis has been one of the most enlightening

concepts in physiology Physiology is largely a group of

mechanisms for maintaining homeostasis, and the loss of

homeostatic control tends to cause illness or death

Patho-physiology is essentially the study of unstable conditions

that result when our homeostatic controls go awry

Do not, however, overestimate the degree of internal

stability Internal conditions are not absolutely constant

but fluctuate within a limited range, such as the range of

body temperatures noted earlier The internal state of the

body is best described as a dynamic equilibrium (balanced

change), in which there is a certain set point or average

value for a given variable (such as 37⬚C for body

tempera-ture) and conditions fluctuate slightly around this point

The fundamental mechanism that keeps a variable

close to its set point is negative feedback—a process in

which the body senses a change and activates mechanisms

that negate or reverse it By maintaining stability, negative

feedback is the key mechanism for maintaining health

These principles can be understood by comparison to

a home heating system (fig 1.11) Suppose it is a cold

win-ter day and you have set your thermostat for 20⬚C (68⬚F)—

the set point If the room becomes too cold, a

temperature-sensitive switch in the thermostat turns on the furnace

The temperature rises until it is slightly above the set point,

and then the switch breaks the circuit and turns off the

fur-nace This is a negative feedback process that reverses the

falling temperature and restores it to something close to the

set point When the furnace turns off, the temperature

slowly drops again until the switch is reactivated—thus,

the furnace cycles on and off all day The room temperature

does not stay at exactly 20⬚C but fluctuates a few degrees

either way—the system maintains a state of dynamic

equi-librium in which the temperature averages 20⬚C and

devi-ates from the set point by only a few degrees Because

feed-back mechanisms alter the original changes that triggeredthem (temperature, for example), they are often called

feedback loops.

Body temperature is also regulated by a “thermostat”—

a group of nerve cells in the base of the brain that monitorsthe temperature of the blood If you become overheated, thethermostat triggers heat-losing mechanisms (fig 1.12) One

of these is vasodilation (VAY-zo-dy-LAY-shun), the

widen-ing of blood vessels When blood vessels of the skin dilate,warm blood flows closer to the body surface and loses heat

to the surrounding air If this is not enough to return yourtemperature to normal, sweating occurs; the evaporation of17

Room temperature falls to 66 °F (19°C)

Thermostat activates furnace

Heat output Room temperature

Thermostat shuts off furnace

60 65 70 75

off at 70°F Set point 68°F

Time

(a)

(b)

Figure 1.11 Negative Feedback in a Home Heating System.

(a) The negative feedback loop that maintains room temperature.

(b) Fluctuation of room temperature around the thermostatic set point.

What component of the heating system acts as the sensor? What component acts as the effector?

water from the skin has a powerful cooling effect (see

insight 1.3) Conversely, if it is cold outside and your body

temperature drops much below 37⬚C, these nerve cells

acti-vate heat-conserving mechanisms The first to be actiacti-vated

is vasoconstriction, a narrowing of the blood vessels in the

skin, which serves to retain warm blood deeper in your body

and reduce heat loss If this is not enough, the brain activates

shivering—muscle tremors that generate heat

processes this information, relates it to other availableinformation (for example, comparing what the blood pres-sure is with what it should be), and “makes a decision”

about what the appropriate response should be The

effec-tor, in this case the heart, is the structure that carries out

the response that restores homeostasis The response,such as a lowering of the blood pressure, is then sensed bythe receptor, and the feedback loop is complete

Positive Feedback and Rapid Change

Positive feedback is a self-amplifying cycle in which a

physiological change leads to even greater change in thesame direction, rather than producing the corrective effects

of negative feedback Positive feedback is often a normalway of producing rapid change When a woman is givingbirth, for example, the head of the baby pushes against hercervix (the neck of the uterus) and stimulates its nerve end-ings (fig 1.13) Nerve signals travel to the brain, which, inturn, stimulates the pituitary gland to secrete the hormoneoxytocin Oxytocin travels in the blood and stimulates theuterus to contract This pushes the baby downward, stim-ulating the cervix still more and causing the positive feed-back loop to be repeated Labor contractions thereforebecome more and more intense until the baby is expelled.Other cases of beneficial positive feedback are seen later inthe book; for example, in blood clotting, protein digestion,and the generation of nerve signals

Frequently, however, positive feedback is a harmful

or even life-threatening process This is because its amplifying nature can quickly change the internal state ofthe body to something far from its homeostatic set point.Consider a high fever, for example A fever triggered byinfection is beneficial up to a point, but if the body tem-perature rises much above 42⬚C (108⬚F), it may create adangerous positive feedback loop (fig 1.14) This hightemperature raises the metabolic rate, which makes thebody produce heat faster than it can get rid of it Thus,temperature rises still further, increasing the metabolicrate and heat production still more This “vicious circle”becomes fatal at approximately 45⬚C (113⬚F) Thus, posi-tive feedback loops often create dangerously out-of-controlsituations that require emergency medical treatment

15 What is meant by dynamic equilibrium? Why would it be wrong

to say homeostasis prevents internal change?

16 Explain why stabilizing mechanisms are called negative

Figure 1.12 Negative Feedback in Human

Thermoregulation Negative feedback keeps the human body

temperature homeostatically regulated within about 0.5⬚C of a 37⬚C set

point Sweating and cutaneous vasodilation lower the body temperature;

shivering and cutaneous vasoconstriction raise it

Why does vasodilation reduce the body temperature?

Men in the Oven

English physician Charles Blagden (1748–1820) staged a rather

the-atrical demonstration of homeostasis long before Cannon coined the

(260⬚F)—along with a dog, a beefsteak, and some research associates

Being alive and capable of evaporative cooling, the dog panted and the

men sweated The beefsteak, being dead and unable to maintain

home-ostasis, was cooked

To take another example, a rise in blood pressure is

sensed by stretch receptors in the wall of the heart and the

major arteries above it These receptors send nerve signals

to a cardiac center in the brainstem The cardiac center

integrates this input with other information and sends

nerve signals back to the heart to slow it and lower the

blood pressure Thus we can see that homeostasis is

main-tained by self-correcting negative feedback loops Many

more examples are found throughout this book

It is common, although not universal, for feedback

loops to include three components: a receptor, an

integra-tor, and an effector The receptor is a structure that senses

a change in the body, such as the stretch receptors that

monitor blood pressure The integrating (control) center,

such as the cardiac center of the brain, is a mechanism that

The Language of Medicine

Objectives

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

• explain why modern anatomical terminology is so heavily

based on Greek and Latin;

• recognize eponyms when you see them;

• describe the efforts to achieve an internationally uniformanatomical terminology;

• break medical terms down into their basic word elements;

• state some reasons why the literal meaning of a word maynot lend insight into its definition;

• relate singular noun forms to their plural forms; and

• discuss why precise spelling is important in anatomy andphysiology

One of the greatest challenges faced by students of anatomyand physiology is the vocabulary In this book, you will

encounter such Latin terms as corpus callosum (a brain structure), ligamentum arteriosum (a small fibrous band near the heart), and extensor carpi radialis longus (a fore-

arm muscle) You may wonder why structures aren’tnamed in “just plain English,” and how you will everremember such formidable names This section will giveyou some answers to these questions and some useful tips

on mastering anatomical terminology

The History of Anatomical Terminology

The major features of human gross anatomy have standard

international names prescribed by a book titled the

Termi-nologia Anatomica (TA) The TA was codified in 1998 by an

international body of anatomists, the Federative Committee

on Anatomical Terminology, and approved by professionalassociations of anatomists in more than 50 countries

About 90% of today’s medical terms are formed fromjust 1,200 Greek and Latin roots Scientific investigationbegan in ancient Greece and soon spread to Rome TheGreeks and Romans coined many of the words still used in

human anatomy today: uterus, prostate, cerebellum,

diaphragm, sacrum, amnion, and others In the

Renais-sance, the fast pace of anatomical discovery required a

Oxytocin carried in bloodstream to uterus

Oxytocin stimulates uterine contractions and pushes fetus toward cervix

Head of fetus pushes against cervix

Nerve impulses from cervix transmitted to brain

Brain stimulates pituitary gland to secrete oxytocin

1

2 3

Elevated metabolic rate Heat production

exceeding rate of

heat loss

44° – 45°C (111°–113°F)

42 ° – 43°C (108° –109°F)

Figure 1.14 Positive Feedback in Fever In such cases as this,

positive feedback can produce a life-threatening loss of homeostatic

control