Human Anatomy & Physiology

1274 Pages·2015·198.374 MB·English

by  Elaine N. Marieb, Katja N. Hoehn

Global Global
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this is a special edition of an established title widely
used by colleges and universities throughout the world.
Pearson published this exclusive edition for the benefit
of students outside the United States and Canada. if you
purchased this book within the United States or Canada,
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Pearson Global Edition
Marieb_fullcover.indd 1 26/02/15 9:10 PM
Brief Contents
UNIT 1 Organization of the Body UNIT 4 Maintenance of the Body
1 17
The Human Body: An Orientation 21 Blood 655
2 18
Chemistry Comes Alive 43 The Cardiovascular System: The Heart 683
3 19
Cells: The Living Units 80 The Cardiovascular System:
4 Blood Vessels 718
Tissue: The Living Fabric 135
20
The Lymphatic System and Lymphoid
Organs and Tissues 777
UNIT 2 Covering, Support, and Movement of the Body 21
The Immune System:
Innate and Adaptive Body Defenses 791
5
The Integumentary System 170 22
The Respiratory System 827
6
Bones and Skeletal Tissues 193 23
The Digestive System 876
7
The Skeleton 219 24
Nutrition, Metabolism, and Energy
8
Joints 271 Balance 934
9 Muscles and Muscle Tissue 298 25 The Urinary System 981
10 The Muscular System 341 26 Fluid, Electrolyte, and Acid-Base
Balance 1018
UNIT 3 Regulation and Integration of the Body
UNIT 5 Continuity
11
Fundamentals of the Nervous System 27
The Reproductive System 1046
and Nervous Tissue 408
28
12 Pregnancy and Human Development 1094
The Central Nervous System 450
29
13 Heredity 1126
The Peripheral Nervous System
and Reflex Activity 505
14
The Autonomic Nervous System 547
15
The Special Senses 568
16
The Endocrine System 615
A00_MARI6971_10_SE_FES.indd 1 3/26/15 5:16 PM
ELAINE MARIEB
is the
most trusted name in all of
A&P. More than 3 million
health care professionals
started their careers with
one of Elaine Marieb’s
Anatomy & Physiology texts.

Now, it’s your turn.
A00_MARI6971_10_SE_FES.indd 2 3/26/15 5:16 PM
LEARN WHY THIS MATTERS
NEW! Chapter-opening Why This
Matters videos describe how the
why this
material applies to your future
career. Scan the QR codes to see
brief videos of real health care
professionals discussing how they matters
use the chapter content every day
<
in their careers.
<
<
A01_MARI6971_10_SE_FM_001-020.indd 1 3/26/15 4:40 PM
SEE WHERE YOU ARE HEADED
NEW! Every chapter opens with a Chapter Roadmap to give you a visual overview
of all the key concepts in the chapter and how they fit together. The key concepts in the
roadmap are linked to the section number in the chapter to make the connections clear.
5
The Integumentary why this
System
matters
In this chapter, you will learn that
The skin and its derivatives serve several (mostly protective) functions
by first asking then learning about and next asking then asking
5.1 What is the The appendages 5.8 What are the 5.9 What happens
<<<Tissues Ch. 4 using
structure of skin? of the skin functions of skin? when things
go wrong?
Chapter looking closer at
looking closer at and finally, exploring
Roadmap 5.5 Hair
5.2 Epidermis 5.3 Dermis Developmental Aspects
of the Integumentary System
and asking 5.6 Nails
5.4 What causes skin color? 5.7 Sweat and
sebaceous
glands
Key Concept Would you be enticed by an ad for a coat that is water- 5.1 The skin consists of two layers:
proof, stretchable, washable, and air-conditioned, that
section header automatically repairs small cuts, rips, and burns? How the epidermis and dermis
about one that’s guaranteed to last a lifetime? Sounds too good
Learning Objective
to be true, but you already have such a coat—your skin.
The skin and its derivatives (sweat and oil glands, hairs, List the two layers of skin and briefly describe
and nails) make up a complex set of organs that serves subcutaneous tissue.
several functions, mostly protective. Together, The skin receives little respect from its inhabitants, but architectur-
these organs form the integumentary ally it is a marvel. It covers the entire body, has a surface area of 1.2
system (in-teg″u-men′tar-e). to 2.2 square meters, weighs 4 to 5 kilograms (4–5 kg = 9–11 lb),
The variation in skin tone shown here is primarily due to
varying concentrations of the pigment melanin.
<
170
M05_MARI6971_10_SE_CH05_170-192.indd 170 3/14/15 3:53 PM
A01_MARI6971_10_SE_FM_001-020.indd 2 3/26/15 4:40 PM
SEE WHERE YOU ARE HEADED
NEW! Key concept organization presents the material in manageable chunks
and helps you easily navigate the chapter. Each section header states the key
concept of that section, and section-ending Check Your Understanding questions
allow students to assess their understanding of the concept before moving on.
Chapter 5 The Integumentary System 171
Hair shaft
Dermal papillae
Epidermis
Subpapillary
Papillary plexus
layer
Sweat pore
Appendages of skin
Dermis Reticular • Eccrine sweat gland
layer • Arrector pili muscle
• Sebaceous (oil) gland
5
• Hair follicle
• Hair root
Hypodermis
(subcutaneous
tissue; not part
of skin)
Nervous structures
• Sensory nerve fiber
with free nerve endings Cutaneous plexus
• Lamellar corpuscle
• Hair follicle receptor
(root hair plexus) Adipose tissue
Figure 5.1 Skin structure. Three-dimensional view of the skin and underlying subcutaneous
tissue. The epidermal and dermal layers have been pulled apart at the upper right corner to reveal
the dermal papillae.
and accounts for about 7% of total body weight in the average The subcutaneous tissue just deep to the skin is known as
adult. Also called the integument (“covering”), the skin multitasks. the hypodermis (Figure 5.1). Strictly speaking, the hypodermis
Its functions go well beyond serving as a bag for body contents. is not part of the skin, but it shares some of the skin’s protec-
Pliable yet tough, it takes constant punishment from external tive functions. The hypodermis, also called superficial fascia
agents. Without our skin, we would quickly fall prey to bacteria because it is superficial to the tough connective tissue wrapping
and perish from water and heat loss. (fascia) of the skeletal muscles, consists mostly of adipose tissue.
Varying in thickness from 1.5 to 4.0 millimeters (mm) or Besides storing fat, the hypodermis anchors the skin to the
more in different parts of the body, the skin is composed of two underlying structures (mostly to muscles), but loosely enough
distinct layers (Figure 5.1): that the skin can slide relatively freely over those structures.
● Touhtee rempidoestr mprios t(eecpt″ivĭ-ed sehri′emldi so)f, tchoem bpoodsye d(e opfi e=p iuthpeolnia)l. cells, is the Solfifd oinugr bskoidni epsr.o Bteecctasu uses obfy ietsn fsautrtiyn cgo tmhapto msitainoyn ,b tlhowe hs yjupsotd ge<lramncies< <
also acts as a shock absorber and an insulator that reduces heat
● The underlying dermis, making up the bulk of the skin, is a loss. Check Your
tough, leathery layer composed mostly of dense connective
tissue. Check Your Understanding Understanding
Only the dermis is vascularized. Nutrients reach the epider- 1. Which layer of the skin—dermis or epidermis—is better
mis by diffusing through the tissue fluid from blood vessels in nourished? self-assessment
the dermis. For answers, see Answers Appendix.
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A01_MARI6971_10_SE_FM_001-020.indd 3 3/26/15 4:40 PM
Chapter 10 The Muscular System 383
MUSCLE GALLERY
Table 10.17 (continued)
Adductors Hamstrings
Vastus
lateralis
(a)
Femur
Posterior compartment of thigh
Vastus
(flexes leg and extends thigh);
intermedius
innervated by tibial nerve (portion
of sciatic nerve)
10
Rectus femoris
Vastus medialis
(b)
Medial compartment of thigh
(adducts thigh); innervated by obturator nerve
Anterior compartment of thigh
(extends leg); innervated by femoral nerve
(a) Muscles of the thigh
Triceps surae
Key:
Fibula
Posterior
compartment
Fibularis
muscles
muscles
Anterior
compartment
muscles
Medial
816 UNIT 4 Maintenance of the Body
compartment
TOOLmuSscles o f thiTgh O HELP YOU P ost eri or OcompartmNent of legYOUR JOURNEY
and lateral
(plantar flexes foot, flexes toes);
compartment
Posterior Goblet cell innervated by tibial nerve
muscles of leg
Mucosa
Pseudostratified Tibialis
ciliated columnar anterior
epithelium
Lateral compartment of leg
NEW! Find study tools online with (prelafnetarr eflnexceeLsa sam ntindoa e pMvroeprartsias ftoeort)i;ngA&P® in the book. Tibia
Visit MasteringA&P for self-study modiunnleesrv, aitnetde bry(ac scountnpiveecertfi ivcaeina tilsimsuea)tions, virtual lab tools,
fibular nerve
and moEsroep!h agus
464(b)< MuscUleNsI TSo uf3 btmhReue clgoeusglaation and Integration of the Body
Trachealis Lumen of Seromucous gland
trachea breakdown reflectisn ssuobmmeu ccohsaange in the capillary endothelial Cerebrovascular Accidents (CVAs)
Practice art labeling
cells or their tight junctions. Anterior compartment of leg
>Study Area>Chapter 1H0yaline cartilage (dorsiflexes fooTht, eex stienngdlse mtoeoss)t; common nervous system disorder and the third
Check Your Understanding innervated by dleeaedpi nfigb uclaaur snee rovfe death in North America are cerebrovascular
Adventitia accidents (CVAs) (ser″ĕ-bro-vas′ku-lar), also called strokes.
Figure 10.26 Summ19a.rWy:h Aatc itsi oCnSFs? oWf hmerue sisc ilte psr oodfu tchede? t Whihgaht aaren idts lfeugnc.tions?
CVAs occur when blood circulation to a brain area is blocked
Anterior20.A brain surgeon is about to make an incision. Name all the
and brain tissue dies of ischemia (is-ke′me-ah), a reduction of
tissue layers that she cuts through from the skin to the brain.
(a) Cross section of the trachea blood supply that impairs the delivery of oxygen and nutrients.
and esophagus
For answers, see Answers Appendix. The most common cause of CVA is a blood clot that blocks
(b) Photomicrograph of the tracheal
wall (320 ) a cerebral artery. A clot can originate outside the brain (from
Figure 22.7 Tissue composition of the tracheal wall. In
CLINICAL the heart, for example) or form on the roughened interior wall
the scanning electron micrograph in (c), the cilia ap1pe2a.r9 as y eBllorwa, in injuries and
graNsMsEl1ik0W_eM p!Ar RoEIj7ea0c4ts0ioi_nl0y9s._ SMfEiu_nCcudHs1 -0sc_el3ci2rn1e-t3ii8nc7ga.i ngld odb l3e8t 3cells (orange) with of a brain artery narrowed by atherosclerosis. Les2s5 /f0r7e/1q4u e1n0:t1l7y ,A M
exashmorpt mleicsro vtiolli ahree linpt eyrsopuer sseed eb ehtwoewen the ciliadteids coellrs.ders have devastating strokes are caused by bleeding, which compresses brain tissue.
Many who survive a CVA are paralyzed on one side of the
A&P concepts apply to your future consequences
View histology slides body (hemiplegia). Others commonly exhibit sensory deficits
career. The clinical content—
>Study Area> Learning Objectives or have difficulty understanding or vocalizing speech. Even so,
Homeostatic Imbalance sections,
the picture is not hopeless. Some patients recover at least part
Describe the cause (if known) and major signs and
A Closer Look boxes, At the Clinic of their lost faculties, because undamaged neurons sprout new
symptoms of cerebrovascular accidents, Alzheimer’s
sections, and Critical Thinking disease, Parkinson’s disease, and Huntington’s disease. branches that spread into the injured area and take over some
lost functions. Physical therapy should start as soon as possible
and Clinical Application questions List and explain several techniques used to diagnose
length of the pharynx acts as a resonating chamber, to amplify
brain disorders. to prevent muscle contractures (abnormally shortened mus-
at thaen de enndha oncfe t thhee scohunadp qteuarl—ityh. Thase aor al, nasal, and sinus cavities
cles due to differences in strength between opposing muscle
alsuo ncoifniterdib untee wto vloocoakl raesnodn afnecee.l .In additBiorna,i ng odoyds feunnucntcioian-s are unbelievably varied and extensive. We
groups).
tion depends on muscles in the pharynx, tonghuaev,e s mofte nptailoantee, da nsdo me of them already, but here we will focus on
Not all strokes are “completed.” Temporary episodes of
lips that “shape” sound into recognizable contsroanuamntas taicn db rvaoiwne ilns.juries, cerebrovascular accidents, and degen-
reversible cerebral ischemia, called transient ischemic attacks
erative brain disorders.
(TIAs), are common. TIAs last from 5 to 50 minutes and are
22
CLINICAL
HOMEOSTATIC (c) Scanning electron micrograph of cilia in the trachcehaa (r2a5c0t0eri)zed by temporary numbness, paralysis, or impaired
Traumatic Brain Injuries
IMBALANCE 22.3 speech. These deficits are not permanent, but TIAs do consti-
Inflammation of the vocal folds, or lar1y2ngitHis,e acadu isnejsu trhiees v aorcea la leading cause of accidental death in North tute “red flags” that warn of impending, more serious CVAs.
folds to swell, interfering with their vibrationA.m Therisic cah. aCnogenss itdheer , for example, what happens if you forget to A CVA is like an undersea earthquake. It’s not the initial tem-
The Trachea
vocal tone, causing hoarseness, or in severe cfaassetse lnim yiotuinrg s uesa tt ob ae lt and then rear-end another car. Your head blor that does most of the damage, it’s the tsunami that floods
whisper. Laryngitis is most often caused by visir aml oinvfiencgti oannsd, btuhte n stoThps es utrdadcehnelay ( tarsa ′ikt eh-aiths) ,t hore wwininddpsiphei,e dlde.s cendst hfreo mco tahste llaatreyrn. xS imilarly, the initial vascular blockage during a
may also be due to overusing the voice, verByr adirny daairm, baagcet eisr icaalu sed nthorto ounglhy bthye l onceackli zaendd i innjtuor yth aet mtheed siaitset ionfu m. It setnrodks eb yi sd invoidt iunsgu ally disastrous because there are many blood
infections, tumors on the vocal folds, or inhtahlaet ibolno wo,f birurtit aatlsinog b y thei nritcoo tchhee ttiwnog emffaeicnt barso tnhceh bi raati nm hidittsh othraex (see vFeisgsuerlse i2n2 .t1h)e. Ibnr ain that can pick up the slack. Rather, it’s the
chemicals. ✚ opposite end of the skullh.umans, it is 10–12 cm (about 4 inches) long andn e2u crmon (-3k/4il liinncgh )e vents outside the initial ischemic zone that
A concussion is an alitner daitaiomne itner ,b arnaidn v feurnyc fltieoxnib, lues aunadll ym toebmil-e. wreak the most havoc.
Sphincter Functions of the Larynx
porary, following a blow toTh thee t hraecahde.a Thl wea lvl iccotinmsi smts aoyf bseev derizazl yla yers thatE axrep ecroimmmenotna l evidence indicates that the main culprit is
Under certain conditions, the vocal folds acto ars l oa ssep hcoinncstceiro tuhsante ss. Atloth mouagnhy ttyupbicualallry bmoidldy aonrgda snhso—rtt-hleiv emdu, cosa, gsluubtmamucaotsea, , aann dex citatory neurotransmitter. Glutamate plays a
prevents air passage. During abdominal stervaeinni na gs eaesmsoincigaltye dm ild coandcvuensstiitoian— capnlu bse a d laaymera goifn hgy, aalninde mcaurlttiil-age (Figkeuyr er o2le2 .i7n) .l eTharen ing and memory, as well as other critical brain
with defecation, the glottis closes to prevepnlet ceoxhnacluastsioionn sa nodv er timme upcroodsau chea cs utmheu slaatmivee gdoabmleatg cee.ll–containing fpusnecutdioonstsr.a Htifioewde ver, after brain injury, neurons totally deprived
the abdominal muscles contract, causing the iMntorare-a sbedrioomusin caol ncusseiopnitsh cealinu mbr uthisaet othcec ubrrsa tihnr aonudg hcoauuts em poesrt- of the orefs opxiryagtoenry b teragcint. to disintegrate, unleashing the cellular equiva-
pressure to rise. These events, collectively kmnoawnnen ats n Veualrsoallovgai’sc al damItas gceil,i aa ccoonntdinituioanll yc aplrloepde al dcoebnrtius-sliaodne.n I nm ucus lteonwta ordf t“hbeu pchkeatr-s” of glutamate. Under these conditions, gluta-
maneuver, help empty the rectum and can aclsoor tsipclainl ct o(snttaubsiilioznes), the inydnixv. iThduiasl empaityh reelimumain r ecsotsn socnio au fsa. iSrelyv ethreic k lamminaat ep raocptsr iaas t hanat excitotoxin, literally exciting surrounding cells
A01_MARI6971_10_SE_FM_t0h01e-0 b20o.inddyd t4runk when lifting a heavy load. brain stem contusions alwhaays sa c raiuchse s cuopmplay, olaf setliansgti fcr ofibme rhso.urs to a to3/ 2d6/e15a t 4h:4.0 PM
lifetime because of injury to the reticular activating system. At present, the most successful treatment for stroke is tissue
Following a head injury, death may result from subdural or plasminogen activator (tPA), which dissolves blood clots in the
subarachnoid hemorrhage (bleeding from ruptured vessels into brain. Alternatively, a mechanical device can drill into a blood
those spaces). Individuals who are initially lucid and then begin clot and pull it from a blood vessel like a cork from a bottle.
to deteriorate neurologically are, in all probability, hemorrhaging
intracranially. Blood accumulating in the skull increases intra- Degenerative Brain Disorders
M22_MARI7040_10_SE_CH22_807-855.indd 816 cranial pressure and compresses brain tissue. If the pressure forces 9/18/14 10:12 AM
Alzheimer’s Disease
the brain stem inferiorly through the foramen magnum, control
of blood pressure, heart rate, and respiration is lost. Intracranial Alzheimer’s disease (AD) (altz′hi-merz), a progressive degen-
hemorrhages are treated by surgically removing the hematoma erative disease of the brain, ultimately results in dementia
(localized blood mass) and repairing the ruptured vessels. (mental deterioration). Alzheimer’s patients represent nearly
Another consequence of traumatic head injury is cerebral half of the people living in nursing homes. Between 5 and 15%
edema, swelling of the brain. At best, cerebral edema aggravates of people over 65 develop this condition, and for up to half of
the injury. At worst, it can be fatal in and of itself. those over 85 it is a major contributing cause in their deaths.
M12_MARI7040_10_SE_CH12_430-484.indd 464 8/14/14 11:31 AM
TOOLS TO HELP YOU ON YOUR JOURNEY
Chapter 9 Muscles and Muscle Tissue 301
Epimysium
Bone Epimysium
Perimysium
<
Stunning 3-D art with
Tendon
Endomysium
vibrant colors appears
Muscle fiber
on every page to help in middle of
a fascicle
you better visualize
(b)
and understand key Blood vessel
Perimysium wrapping a fascicle
anatomical structures
Endomysium
and their functions. (between individual muscle fibers)
9
Muscle fiber
Fascicle
Perimysium
(a)
Figure 9.1 Connective tissue sheaths of skeletal muscle: epimysium, perimysium, Practice art labeling
164 UNIT 2 Covering, Support, and Movement of the Body a(Fnodr ae rnedlaotemdy imsiuagme., (sbe)e PAh oBtroiemf iAcrtolagsr oapf hth oef Hau cmroasns sBeocdtiyo, nP loaft ep a2r9t. )of a skeletal muscle (30×). >Study Area>Chapter 9
of the external environment. This slows passive heat loss from Excretion Let’s consider these connective tissue sheaths from exter- Attachments
nal to internal (see Figure 9.1 and the top three rows of
Recall from Chapter 8 that most skeletal muscles span joints
the body, conserving body heat. Chapter 24 discusses body tem- NEW! Making ConneTcabtlie o9.1n).s questions in each chapter aansd katt aycho tou b otneos ( oar opthper lsytru cwturhes)a int a t least two places.
perature regulation. you’Thwveae slt eebsao r(dnayme edmli maoncirniaoa,s tues srd e●l aiifmmtE,h pfuaaiemtsi ncstylrueesdr”eir)udo minusu .na artndTi m sh“ cobtevh oeeeoar pcwucidomhianotdyy”lste oi) sumfs m diuyeon sn(csfes letep s. ″ ienwSrĭ-romemimegtiuresal′tsoaietmr- , guca eomasen ni;lnn tt “edboh-cluetc oitnvscodeiud shtne iwgs sattiuhhtaheep imnteiontmWrisgosuhtns e c,sn lme oa’so mov reutissg hctiloneaw. cIaontrn d tth yrteah comet siu,um tshcm leeb oms vouoafvb taliheble ldo elri bm loeabnssse, ,mt thhoee v omarbiuglesin cbl eto’ysn pieni,c satehlrlye-
cohessuicvhe wuansdtees rasrtea enxdcrinetged toh ei fnd e teuph fraesicni abe th.o aPt dliresyo b.feutwseee<n snewighebaortiinng mgu iscsle as onr thime polire-s proximal to the insertion.
Cutaneous Sensation superficial fascia deep to the skin. Muscle attachments, whether origin or insertion, may be
tant avenue for water ●a nPedri msyasilutm ( asnod dfasicuiclmes. Wcihthlino eraicdh esk)el eltoal smsu.scle, the direct or indirect.
muscle fibers are grouped into fascicles (fas′ĭ-klz; “bundles”) ● In direct, or fleshy, attachments, the epimysium of the mus-
The skin is richly supplied with cutaneous sensory receptors, Check Your Undtehart rsestemabnle dbunidnlegs of sticks. Surrounding each fascicle is cle is fused to the periosteum of a bone or perichondrium of
a layer of dense irregular connective tissue called perimy- a cartilage.
which are actually part of the nervous system. The cutaneous sium (per″ĭ-mis′e-um; “around the muscle”).
● In indirect attachments, the muscle’s connective tissue
receptors are classified as exteroceptors (ek″ster-o-sep′torz) 21. What chemicals pro●d Euncdoemdy siinum t. hThee senkdionm hyseiulmp (penr″odov-midise′e -buma;r “rwieitrhsin to wrappings extend beyond the muscle either as a ropelike
because they respond to stimuli arising outside the body. For bacteria? List at least trthoheu nmrdeuse seca leca”h)n iinsd da i vewidxisuppayll asmhiuenasct hlhe ofoifb cweorn. Intt ehccoteinvs eic stthiss soeufme f itnhieac taa rseulosr-- are tneun-droo′ns is()F. iTguhree t e9n.1dao)n o orr aasp oan sehuereotsliiks ea nacphoonrse uthreo smisu (sacple″ oto-
protective. lar connective tissue. the connective tissue covering of a skeletal element (bone or
example, tactile (Meissner’s) corpuscles (in the dermal papil-
As shown in Figure 9.1, all of these connective tissue sheaths cartilage) or to the fascia of other muscles.
lae) and tactile discs allow us to become aware of a caress or 22. Which epidermal cealrles c opntlianuyo uas wroithl eon ien an botohedr ays wimell ams wuitnh tihtey t?endons that Indirect attachments are much more common because of
the feel of our clothing against our skin, whereas lamellar (also 23. How is sunlight impjooonin trh tmeasuens scthle esta ottho s ,bb woonheincsh.e Wt rahhneesnma miltt uthhsce?l ep ufilblienrgs fcoorncetr taoc tth, eth beoyn peu toll tlahgeeirn dfuibrearbsi lwityh iacnhd c samn awlli tshizseta. nTde ntdhoe nasb araresi omno ostfl yr otuoughgh b coonly-
called Pacinian) corpuscles (in the deeper dermis or hypoder- 24. MAKING connectionsbtiec imWtyo ovhfe mde.u nTshc lebe stlhiosesaoutehd,s a c novdne tarslisbsoue ptelrs osv oiimdnee wrtohhuatete ts o df othre etr hnmea teunirstar lyc e aolansnd- stricpsutroe sje. cBteiocnaus steh aotf wthoeuilrd r etelaatri vaeplayr st mthael lm siozree, mdeolircea ttee nmduosncsl et htiasn-
mis) alert us to bumps or contacts involving deep pressure. Hair or dilate to help maeixnit toaf tihne bblooodd vye stseelsm anpd enerravet ufibreers, thwat hseircvhe t htey mpuesc loe.f
follicle receptors report on wind blowing through our hair and muscle tissue that you learned about (in Chapter 4) acts as the
effector that causes blood vessel dilation or constriction?
a playful tug on a ponytail. Free nerve endings that meander
throughout the skin sense painful stimuli (irritating chemicals, For answers, see Answers Appendix.
M09_MARI6971_10_SE_CH09_298-340.indd 301 3/14/15 4:09 PM
extreme heat or cold, and others). We defer detailed discussion
5
of these cutaneous receptors to Chapter 13. CLINICAL
5.9 Skin cancer and
Figure 5.1 illustrates all the cutaneous receptors mentioned
above except for tactile corpuscles, which are found only in skin burns are major challenges to the body
that lacks hairs, and tactile cells, shown in Figure 5.2b.
Learning Objectives
Metabolic Functions Summarize the characteristics of the three major types of
A01_MARI6971_10_SE_FM_001-020.indd 5 skin cancers. 3/26/15 4:40 PM
The skin is a chemical factory, fueled in part by the sun’s rays.
Explain why serious burns are life threatening. Describe
When sunlight bombards the skin, modified cholesterol mol-
how to determine the extent of a burn and differentiate
ecules are converted to a vitamin D precursor. This precursor first-, second-, and third-degree burns.
is transported via the blood to other body areas to be converted
Loss of homeostasis in body cells and organs reveals itself on the
to vitamin D, which plays various roles in calcium metabolism.
skin, sometimes in startling ways. The skin can develop more
For example, calcium cannot be absorbed from the digestive
than 1000 different conditions and ailments. The most com-
tract without vitamin D.
mon skin disorders are bacterial, viral, or yeast infections (see
Among its other metabolic functions, the epidermis makes
Related Clinical Terms on pp. 171–172). Less common, but far
chemical conversions that supplement those of the liver. For
more damaging to body well-being, are skin cancer and burns,
example, keratinocyte enzymes can:
considered next.
● “Disarm” many cancer-causing chemicals that penetrate the
epidermis
Skin Cancer
● Activate some steroid hormones—for instance, they can
One in five Americans develops skin cancer at some point.
transform cortisone applied to irritated skin into hydrocorti-
Most tumors that arise in the skin are benign and do not spread
sone, a potent anti-inflammatory drug
(metastasize) to other body areas. (A wart, a neoplasm caused
Skin cells also make several biologically important proteins, by a virus, is one example.) However, some skin tumors are
including collagenase, an enzyme that aids the natural turnover malignant, or cancerous, and invade other body areas.
of collagen (and deters wrinkles). The single most important risk factor for skin cancer is
overexposure to the UV radiation in sunlight, which damages
Blood Reservoir DNA bases. Adjacent pyrimidine bases often respond by fus-
ing, forming lesions called dimers. UV radiation also appears to
The dermal vascular supply is extensive and can hold about 5%
disable a tumor suppressor gene. In limited numbers of cases,
of the body’s entire blood volume. When other body organs,
frequent irritation of the skin by infections, chemicals, or physi-
such as vigorously working muscles, need a greater blood sup-
cal trauma seems to be a predisposing factor.
ply, the nervous system constricts the dermal blood vessels.
Interestingly, sunburned skin accelerates its production
This constriction shunts more blood into the general circula-
of Fas, a protein that causes genetically damaged skin cells to
tion, making it available to the muscles and other body organs.
commit suicide, reducing the risk of mutations that will cause
sun-linked skin cancer. The death of these gene-damaged cells
causes the skin to peel after a sunburn.
M05_MARI7040_10_SE_CH05_150-172.indd 164 21/07/14 10:04 AM
PRACTICE MAKES PERFECT WITH MasteringA&P
NEW! Concept Maps are
fun and challenging activities
<
that help you solidify your
understanding of a key
course concept. These fully
mobile activities allow
you to combine key terms
with linking phrases into
a free-form map for topics
such as protein synthesis,
events in an action potential,
and excitation-contraction
coupling.
<
NEW! Interactive Physiology® 1.0 and 2.0 help you understand the hardest part
of A&P: physiology. Fun, interactive tutorials, games, and quizzes give you additional
explanations to help you grasp difficult concepts. IP 2.0 includes topics that have been
updated for today’s technology, such as Resting Membrane Potential, Cardiac Output,
Electrical Activity of the Heart, Factors Affecting Blood Pressure, and Cardiac Cycle.
A01_MARI6971_10_SE_FM_001-020.indd 6 3/26/15 4:41 PM
PRACTICE MAKES PERFECT WITH MasteringA&P
A&P Flix™ are 3-D movie-quality
<
animations with self-paced
tutorials and gradable quizzes
that help you master the
toughest topics in A&P.
Practice Anatomy Lab™ (PAL™) 3.0
<
is a virtual anatomy study and practice
tool that gives you 24/7 access to
the most widely used lab specimens,
including the human cadaver,
anatomical models, histology, cat, and
fetal pig. PAL 3.0 is easy to use and
includes built-in audio pronunciations,
rotatable bones, and simulated
fill-in-the-blank lab practical exams.
A01_MARI6971_10_SE_FM_001-020.indd 7 3/26/15 4:41 PM