Human Body, The

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Your Amazing Body ........................The Body's Building locks ..................Your Skin-Jack of Al rades ............... .Your Skeleton-Support and Protection ...........Teeth-Food Cutters, Crshers, and Grindes ........Your Muscles-the isse That Movs ou ... . ....Your Thirtyfoot Digestive System ..............Lungs-o Beath of Lfe ......... ... ...Your Body's Bood Pmp ..... .. ............Kidneys-Your Body's Filtration Plant ............Brain, Nerves-Your Communication Syste ........Seeing, Hearing and Other Senses ............The Endocrine yste-Cemical Contol ..........More of a Kind ..... . .... . ............46 -


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AGOLDEN EXPLORING EATH BOOK

THEHUMANBODYAl about heinside andoutside of thebodytat

is ou. A ascinatinglook at the heart, brain, boemusce, skin and uch ore-tol in asytoread

tex and lavishly ilustrated in fu oor.

By Geoge S. FicteIlustrated by Ralph E RicketsCove by Rod Ruh

GOLDN PRESSWestern Publishing Company, Inc, Racine WsconsnCopyright 1977 by Western Pulishing Company, Inc. All ights esevedNo part of his book may be reprodced or copie n any fom without

written permission from the publisher Printe n USA.

GOLDEN PRES GOLDEN an A GOLDN XPLORING RTH BOOK e taemaks ofesern Publishing Company Ic


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Your Amazing Body

From the time of your bith, and for

as long as you live, your body is neve

completely at rest Every second, yourbody is using energy Moving your arms

and legs takes energy The beating of

your heart, the blinking of your eyelids,

the reading of this book kind o

activity requires at least some energy,which comes from the food you eat Youalsoneed food for growig andfor repair-

ing yur body Wha is mos amazing is

how your body provides energy, growth,and repairs, using only food you eat

Your body is composed of billions oftiy living uits called cells There areay kids of cells in your body Thosecells that are alike and work togetherform issues Tissues, in tu, form largeruits called organs rgans are groupedinto larger units called systems Together,

he systems form your bodye of these systems is he skin, theprotective outer covering of the body Inadditio, the skin also contains importantglands, serves as a place for the storageof food reserves, helps to regulate the bodyteperature, and conains many nerveedings that respond o touch, pressure,pai, hea, and cold

The skeletal systemthe bones of yourbodygives your body its shape and formIt protecs vital parts, such as your brain,heart, and lungs, and it gives anchoragend leverage for all the musces you se.

movgT scr y -

eral tes of muscles Those attached directly to the big bones of your skeleton,

as in the arms and legs, can be oved awill ther muscles are thin, lastic sheetsthat help give our bod its rmness an

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sae till others, such as the heart, dt

h r

r

uomatially You have nocontrol oer them.

n the digestive system, fds ar

cange into simler forms that can buse y he body. The rinci arts fis ssem are the mout, stomach, andiesines.

e lugs, windie, and arts of thnose and throat form th resrary sys-tem. Its jo is to provie the blood with

oxygen and remove caron dioxid, awaste gas.

he cicuatory system consists of thheat, arteries, veins, cillaries, and bod.Tis system carries the oxygen and fdsustances to cells thrughut t bdy.It also carries away waste prdu fm

the cellsWastes are remve frm h body b

the xcretory sysm. Many wass ar r-

mvd frm h ld b h kdys.

The lungs and te kin aso emtewastes, and solid wastes pass frm t

igestive trac.

Thebrain,spil ord, adnrs mak

up hnervous system. This is hecomlex

cmmunications network wth whc yos, hear, ast, touch, and snse your

srroundings. As, the bra i capable

f hiing and rememerng Wihohes abiliies ud n b a ead thi bok Scinis fe a brain is, f many reasons, probably the

ms mpra ga t bdTh ndrn m

fered as h bod's chemical control.Tis systm is cmsed ntirey f small,speial glands found in various laces in

yur bdy. h secrtins o th glandsr aled hrmones, whih detemineur rat of grwth nd cntr many oth- bdy avs

Fnay, te reprductv systm maks ssb fr hman beings" t cratenew uman beigs. It consists f he testesn the male and the ovaries and uterus in f.

T vr ss dof mon ad os of dividua

cel, work rcuou hrmony to

keep your body fuctioing.

Although we aresimlar n structure, each of usis a unique perso.


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We are made of bil l ions of cells of

dierent knds. Some of them look

ytopasm

c l l-

ebrane

The Bdy's uildng BlockA iving things are organied into very

smal units caled cells. The simpest plant

and animas consist of a singe cel. Your

body is composed of biions of cells.

One drop of blood, for example, contains

ore than a illion red blood cells.

Cells are coposed principally of pro

toplasm, a grayish, jellylike, amazinglycompex subsance. Many eleents are

involved in the coposiion of protoplas,

bu he ost coon are carbon, hydro

gen, nirogen, and oxygen.

bo seveny percen of prooplas

s . os auda su

sances r he diere kinds of proeins.

Proeins are called he building blocks of

all life. Sugars, sarches, and fats, the oh-

er ain subsances of protoplasm, are he

foods ha he cell uses o produce enery.

Sats, vitamins, and a number of other

substances occur in protoplasm in lesser

and oen minute amounts, but they are

of vitl importance.

Most cels are arge enough to be seen

wih an ordinary microscope. The typical

animal cell consists of hree maor parts:

the nucleus, cytoplasm, and membanes.Within the cell is found a dense, tiny

ass of rotoasmhe nucus, held

ogether by is mebrane. Surrounding

he nucleus and making up he bulk of

every cell is a ae prooplasm calledcyopasm. Hod e yopa o-

gether is an ouer wall, or_ cell embrane.

The nucleus is the contro center of the

cell. In it are a uber of slender, dark

hreads called croosoes. These are

coposed of still saller units the enes.

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ne ce Hw a CDd M

tat abot to millio rd blood clls diead ar rplacd ve scod.

Body clls divid by a procss calldmitosis ic occrs cotiosly i t

body. Firs t cromosom materials it cls of t cl bcom ll or-gaizd to ditict trads. Eac cromo-some trad divids ad forms idticalpas. T t mb aod ts disappars. T pr of coo-soms sparat o from a par mov

Chomosome pas sepaate. Nucleu membae om; ce dvdes. wo cel

Gs ar so tiy tat ty caot b s

v magid tosads of tms.Gs dtrmi t caractrstics of tcll. Ths fatrs ar passd o th cll divids. Ty ar also passd ofro parts to tr yog.

T cytoplasm cotas fats, gars,starcs, prots, salts ad otr sb-stas. I t ytoplasm too ar bbb-k spas cald vacols. Som of ts

vacols cotai foods tat ll b sdby t cl. Otrs cotai asts to blimiatd.

T exact compsitio of te cyoplasmis alays cagig, for eac cll acts ka t cmica factory. t accpts ra ma-trials ad covrts tm ito sabl sb-stacs ad t limiats t asts tatform. I pars of t body ta ar gro-ing or tat ar rplacig tmslvs as olds , t s dvdg costaty.I t blood or xampl, it s stimatd

6

g toard t oppost d of t cll.

W t cromosoms rac t oppositds of t , ty form ty clstrs.A mmbra forms arod ac str,formig a cls. A ll a t

_

pprs bt t to c. No trr to parat s, a otg at dcto of t rooo -ts t orgal cll. l ts ap-ps a or or s.

body s ompod of ay dr-t kds of cs, ac typ avig sp-cial fctio. Mscl cls av t ablityto otract or cg sp, c aksot possb. N r tsmt p o st. dcs prodc varos kds of scrtos.Rd bood lls carry lg qatt ofo d rlas t for dd. Wt blood cls absorb ad d-gst ds ogasms. So dst tsimarits basic composto, t clls


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ofthebodydodier intheir appearance

and function.

ells of bout the same size and shapend hving the same function are

grouped together to form tissus Manyuscle cells grouped together, for xam

ple, form muscle tissue Te groups of

musclecells are held together by cells of

another type that form connective tissue,

which is common throughou the bodyBlood is a liquid tissue

Tissuesform stilllarger, more complex

units known as organs The heart, stom

ach, liver, nd intestines are examples o

organs Most organs consist of several

kinds of tissue, but ne generally domintes The brain is principally nerve tissue; te stomac and the heart consistmainly of mscle tissue

Groups of organs form body systemsThe digestive sysem consists of hemouth, stomach, the small and large intestines, an various other digestive organs, all orking together to accep anddigest ood

So simila cells form issues ha aregouped ogether o form organs Organsmake up the sysems tha form he ody

ach of the major sytems of the body isdescribed in the folloing chapers

F o th Mny Kinds o Cs Found in th Body

gand ce(stoach)

smoothusce cs(stoach)

ces7


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faty

issue

kJk Al sour skin is one of he mos remark-

able of all he body sysems Toally, an

adul's skinweighs abou six pounds, and

if stretched ou, i wouldmeasureseveral

square fee I consiss o many billions

of cellsour skin covers and proecs he enire

oe urace o you body I ee e-nds inside insome areasino your ears,

for insance he skin is hickes on he

soles of your fee, and i ay be eve

hicker if you go barefooed a lo

ver mos of your body, every squareinch of skin coains may swea glands,

8

several dozen oil glands, abou hree feeof tiny capillaries carrying blood o andfrom he skin, as many as welve fee of

neves for sensing hea, cod, touch, pres-sure, and pain, and many housands ofskin cells

our skin is composed of two layerse o ayer e eder, cconsiss mosly of dead cells ha are con-sanly being sloughed o Every day, youlose lierally milios of old skin cells Ina lifeime, you shed your ouer ski seven

or eigh ies, bi by bi eing rid ofhese dead cell is a aral process The

nerve

budle


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very outer portion of yur skin is alsothe part that peels o whe yu sunbu.The cels iediately beneat tis laerare alive ad are constantly dividing. They

provide the new cels that keep the skinclean and bright.Spread ver the outer layer of the skin

is a thi l of oil tht cmes fr glandsroud the hirs. Soe people produceore f his oil ta do oters The ilacts as a lbricant tat keeps the skiso, pliale, and

wat rof.

The ch thicker layer of skin under

the epideris is called e dermis. It con-tais the lood vss ls, eves, sweatglands, and connective tissue that joinshe deris o the epideris all raised

areas, or ridges, are formed by this coective tissue These ridges are what giveeach perso his distinctive ngerprints,ike aye else's. These ridges alsocoi the erve edigs for touch dsiilar eios.

he y are h, you perspire Moreth two illi litle sweat glads i yorsi pur t iuids s te perspiraionevore, you re cooled f you perspirech, yo il eel he eed fr a drink ofer r ody demds el_ce

e h ot uid yo did o erir, or ody wold ece overheed col ys, te swet pres remaicosed, a you perspire very little or ott all.

Persirio i o just wer, o courset ls cois vrios wate salts, cids,and other ubstces, s of e ore e od. e wa r

evaporates fro the perspiration,these substances are le as a salty residueon the srace of the si.

You re also cooled y e action fe iy lood essels i or sin. e

you are t, tese little blod vesselsdilate, or enlarge, exposng a greateraount of blod to te coling ai. Thisis what makes you ushed, or red in the

face, wen you are hot. I cool weather,the bld vessels cntract and remain deepin the skin.

The skin is clred by a pigentcaled melani. Peple who have a lot ofmelani in teir skin are brwn to black.Melanin and anter pigment make areddis or yellwis skin. People with lttle or no elnin in teir skin are wite

or even pikih, if their bod vesselsshow troug Freckled pele ave spots

oop

arch

whor

Each person has unquengerpnts. Howee,a ngerprints can begroupe into one o treetyes: arc whor anoo


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of eanin in eir skin sunanned per-o ore an e usua amoun ofeann bease e skn as produced ias a proeion agains bg from e

suns raysMelanin is also e pigen a gives

air is oor Te more melanin, edarker e air en meanin is ixedwit a re pigen, e resus are varioussades of brown f elanin is aking,e air ay be blond or red Hai onsiss of e air sa, an oil

gand, and a iny use a an erec

e air and also fore oi from e glandIf you beome frigened, your air will

Whe n you are frig hte ne1

hi r muscles conract,

cusin g the h air oi

on en " and go sf bu

to for.

"sand on end, or you wi ge "goosebumps over your body Tis appenswen e muses around te bases of eairs onrat and igen

Hair stars its gow fro seia elsin e deris Soon e new air pusesroug e epiermis, growing in a iepoke, or ube, aed a folie The airiself is a rod of dead els, u te ase,or roo, is living and is supplied wilood vesses

You probably ave a leas a uarer ofa million airs on your ody Soe peo-

ple ave more an oersup o as manyas alf a milio Mos f ese irs arevery sma and wiis; oters are argeTe air on yor ea gows about sines a yearore an a on somepeope, less on oersand a bi faster insummer an in winer

Mos airs are sed and repaed aregular inervals bou four years s e

average eng of life for a air on youread Eyelases las only abou six monsYour ngeals are aso ougros of

your epidermis Te ouer par of e nailis dead, bu e roo is alive and is riysupplied wi lood vesses is osan-y produing new els and pusing enai ouward In a ealy person, nger-nais grow abou wo ines a year fyou never u yor nls, tey woud be

abou en fee ong by e ime youreaed e age of sixy!


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keletpp d e

f you were given the task of putting abody together, you would start with the

bones. Put together properly, they wouldfor the skeleton, the fraework that sup-ports the body and gives it shape.

Parts of your skeleton also serve i-portantly as protection for delicate partsof yor body. Your brain, for exaple, isecased in the boxlike craniu of yourhead, and your heart, lungs, and soeother vital organs are contained in a cage

of bones fored by your ribs. n additio,the uscles you use in oving are at-tached to the bones of your skeleton, alsogiving the usces their leverage. Finally,the arrow in the hollow boes of yourbody anufcures both red and whiteblood cells.

Totally, your skeleton consists of 00bonesor 06 if the tiny boy parts of

the inner ear are counted separately.Many people are surprised to learn thattheir bones are not solid, dry hard, anddead. Rather, ost boes ar hollow orat least spongy inside, and, though r,any are exible. Further, they are veryuch alive, containing blood vessels adnerves as well as active dividing bonecells. Bone is indeed a living tissue.

Bone cells divide constantly to replacethose that are old and wornout. f youbreak or fracture a boe, the body beginsiediately to ake repairs. Doctorshlp by "setting the bone an holding itin place with splints or a cast t ake cer-n that heas straght.

The bones of our body can be dividedinto two group: (1) those that provide

aily support and protection and havelittle o no oveent, suh as the skullackbone, and chst bones and those


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r

he ando jnt-el

ballandcketjont manmovementh

vbl, su s n, a, lg bns

in ns t isl n Muss n lgans,i ug sns f nniv is-su, n bn n-r crss n s s bns in l Wn usl nrts,n bn vs ta Wn usl rlaxs, bn mvs baku n s is asiy by liing yur

lr yu sulr bnu th

lb yu us bipsusl i yu u

lhl lejcke

T ns f bns v ia ug ban a vns

frm ubbin itly ginst rat t ins Mst ins ls ninusins f arilag, lus a sallaun f ui, riing int ra smy w dn dm

T s famila an s fly v-ing y f int is ballnskty is is ty y av in yur an in yur sudr kn f

ints in yur lbs an nrs tlik sil ings y n v up nn bu in nly n iin


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es f e

e e e yu u u

.ou kul f cnu, h f, lg, belowe jaw. Te anu, sg e lbain, foed of x tufaed,cued bones. T jggd edge of ebones tgly toge o t s df-cult to see te sepaae boe. (n new-bon babes, hese bones e no ye gwntogethe in soe places. Te ae e"so spots in the baby's ed.) t tebase of te canu n te ea s a lgeopnn, te foaen agnu, toughwch the spinal cod and lage ateiesand vens pas. T font of te canufos the foehead.

A f f f , , e p Tep w

ei. S-e ke fee, geple wh lleg.

Th lowr jaw, or mndib, is rge

oep bne I is igo skull s hen obleku e.

upng u f uskeleo s you kne o eolun t n f yee bones eebe Tee ae even kveeb, tele n e est o o,ve n e le bk, ve oe efused to fo te sacu to whi the pel-vs s aaed, and fou (o aely e)sal bones tat a fused and f a so

Th ku dut

Te por t on that covers te brain is ca l le d te

cranium. Fac e bones and lower jawbone make up

the ba a nc e of th e sku l l . The lower jwbon e is

the o ly movable bo ne.


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tas, rst ervierterasuorts su

torac verter

nt t, r cccx. wn t verte-

br ar scksrbg scs f crage.f s scs s ut f c, r "s,t c t nrvs. s s ex-tr nu n sts cn b cr-rct n b surgr.

e rst neck vertbra s cle thes us t surstgt ft

. t s a rng f bn wt tw brdrjctns n te ur s. e edcn v back and frt r d n tsercts.

Ast a f vrtbr ve letrug wc t sn cr asses.Ners cnnct t tsn cr by en-erng trug enngs alng each sde t verterae. A netwrk f b vessess fws tse cns.

Also pr of the main, or suportng,

skletnstrbcge, frme f twenty-

four sndr, at, curvd ribs-twlve on

sid. A r ttcd to t back-

4

ervi verter

uar vertera

bne. n frnt, te rst sven are n

t brste,

r stu. nxttre r n t t ec f cartthat s n tu attace t te brstbn.e ast tw are te saled tng rbs,whc are nt ttac t al n frn.Neter s as lng as te ter rbs. hsbny cage surruns te eart, lungs, antr vta rgans f te cst.

In each suer ar fun tw bneste clarbne (cavce) an te sourb scu). clrb s t t rstn. xct r ts cc-tn, tese tw bne tat fr chsuer re e n pace n b usces.Te ar bnes attach t the scaula by abalandsckt nt at te rt. snt aws a grat ea f vnt, andt rs n b vted n st evdrectn.

The bg bne f t upper ar s tuerus. w t ar tw bs, t ua


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and the radius, fring the lwer ar.

These are the bnes that can be pivted

acrss each ther, peritting yu t twist

yur lwer ar. Eight sall bnes, called

carpals,' fr the wrist, an the pal fthe hand cnains ve lng etacarpals.

Attached t each f the etacarpals are

the bnes f a nger. There are three

bnes,r phalanges, ineach ger andtw

in the thub.The thub is unique. The etacarpa

bne t whih it is attae is set in a

dierent directin fr the ther eta

carpals, and it can ve freely. This ppsablepsitin f the thub allws yu

t grap and t anipulate bjects. This

is ne f the utstanding featres that setan apart fr all ther anils.

r hipbnes are stury in strctre,

on o

th Hnd

fr they supprt the bulk f the bdyweight as well as allwing fr attachentf the legs. The hips are fred f tw

large, slid bnes the pelvics. They are

jined t the sacr, the fused bnes fthe vertebral clun. In each pelvic bnethere is a ballandscket jint fr cnnectin with the lg bnes.

The heay, tpt bne f he leg ithe feur. It is the largest bne in yrby. he lwer leg cnsists f tw bnethe sli, rlike bula an the arerat tibia, r shinbne. etween the tibia

and the feur is te sall, at patela, rkneecap he bla an tibia are bunclsely tgether and cannt rtate ne the ter a the lwerabnes an.

The bnes f he feet are uc likethse in the hans. ere are even tarsalr anke bnes. Cnnecte t tese are teetatarsa anten the paanges rte

bnes. he large te, lke the thub, anly tw bnes. A the th

er tes havethree bones. Because te foot is arched,

uch f the shck is absrbed when ywal. Shes with high heels thrw the

weight f the bdy frward and destryuch f the eectiveness f his arch.

on o

the Foot

ones o ane,

o etaas

toe bones,or haanges

etatarsaones 1


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eetFd tes, es, Gdes

u ere b tless. ur sttt rbbly pered e yu ere

but six mts ld, d it my vebee s lg s t yers befre yu dyur mplete set f tempary teet

16

tety i ll. y te time yu ee sixyears ld yu began t lse tis set

teet d get yur perment teet butsmetimes te lst f te temprry teetre nt sedutil age te r eleve.

Te temprry teet are pused ut sermaet teet me i t reple tem.Tis set is almst mplete at age twelver titee. Oly te salled wisdmteet, e ea side at te rer f teuppr nd lwr aws nt ap

peared. Tey usualy pus trug tegumssmetimes pifully ad eedingelpdurig te late teens. Oen teyme in rked beause tere is teug spae fr tem in te ja. Smepeple ever get teir ism teet, butif tey d, teir permanet set teetsists f tirtyt teet.

Teet re red rmly in skets ur aws. Te ardest part te tot iste uter vering, r emel Tis is teprt f te tt tt ss. Te rtsre vered it similr rd substelled emetum. eet te enmel feac tt is te ivryike deti wimkes up te bulk f te tt. In teeer is te pup vity, ntinig r-

eries, veins, nerve edis.ur eit frnt teetfur bve d

fur belre lled inisrs. ey vet, edgesped edges fr uttig siig. On e sie f e iiss bt te upper and lwer ws is a pitedspid r anine Te canines elp tearfd fr ewig. Next t tem re tebiuspidseigt ttlly, t i e lff te uppe and ler jas. Tes tetel totar, gind ndcrusood. But t

rincial j b grinding d isdonyte brad mlars. Te mlars are te last


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C. oarsuse to gr n foo

B usps an uspsuseto tear an rus foo

teeth. here are tw n each side in theupper and lwer jaws, and if the wisdmteeth appear, anther mlar is added teach jaw n each side

In an ideal set f teeth, the upperteeth verlap the lower teeth slightly. ften teeth cme in crked r are nspaced prperly. Evn slight mists that

can at rst be tlerated may cause trublein later life. In mde dental practie,these cnditins are crrcted as sn aspssible Teeh h gee propee eeed o god healh t impr good digein ha od be wel chewed wwd cd popel i eeh l cobegreal o gd appeace

Cavities are tth decay caused by anacid that frms as a result f bacteria feed-ing n particles f in th uth. his

ee an du

A sosB usp s

uspsC oars

A Insorsuse to ut foo

usually curs when fd becmes ldgebetween the teet r at the gum line, butit may start wherever there is a tn cacin the enamel he bacteria, which arenrmally present in the muth, feed a-mst mmediatel n sugars. Fr this rea-sn, it is imprtant t brush yur teethaer every meal If this is nt pssible,

yu shuld rinse yur muth well withwater t get rid f fd particles, especiallythe sugars

fter the acid eats away the enamel,e decay ca mve ino e se deinhere the decay cntinues at a much mreraid rate. If nt st d, i rece epulp cavity and begns t be painful. tis imprtant t hae teeth checked reular-ly b a dentis Prevei is muc wiseand less cstly than waiting serioutrubles develp


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Msee sse a ves

If smene asks u sh ourmusle, u ll usuall ex ur arm t

sho o te sze of our beps, the bgmusle n our per arm Yo probablnever thnk abt ho man other musles have n ur bo Toall, there areabout 600 Alost all of the "esh ofo bo s msle Muses aot forughl half our eght

Yo epen on your msles for evermove u make. Msles open an sht

or ees an move or eyeballs; thekeep u bl movng help yo geso f, move your ars an legs an

u nges and toes Evy kn of m-on nvlves at leas one musle

Yu ave thee erent kns f muslesn ur bvolunar, nvoluntar, anheat, r ara, musle.

Vunta musles ae tose ha mvenl heny ee to mve them ahf he man, man lng els formng themusle ontansman nule, smetmes a

hunre rmre. Ths knfmusle s

als alle asrate musle beause, hen

seen uer a mrospe, he ells appearto ave strpes o bands.

The musles of ur arms an legs arevoluntar musles Your beps, as a yp-al exampe, ossts of an enlarged md-dle poton, o "belly, and taered eds

he part attahe to the mos statoarron f the skeleton s alle the gn.

8

usle

ounty,o sooth

u Cl

outy, ostted

d


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fnsertion

The oher end, aached o the more mov-

able par of the skeleon, is known as he

insertin. These muscles are connected to

he bones by tendons which are strong

and exible bu do no streth.

Involunary muscles are those ha movewihou your conrol. Those hat move food

hrough he digesive ac or tha dilae

or resrict he size of blood vessels are of

his sor. These are also called smooh

muscles because heir cells do not have

cross sries. Eac smoo muscle cell con-

ains only one nucleus.

Hear, or cardiac, muscle is a special

ype. is crosssriped, or stiaed, ye iis involuntary. You have no control over

its movemens.

Yu heat is the mt mable m

l i by. t t

hous da, ming blod tg y

body ith each beat. Ever year yr

heart beats or contrats abt fory mil-lion times and it may operate for eighty

years r longer withou dculty. In that

length of ime it will pump about sev-

enty millin gallns of blod hrough

your bdy.

Muscles cause mvement by contat

ing. When you li you arm, the big bi-

ceps muscle in your upper arm contract

and pulls the forearm upward. t the sameime, the ticeps muscle on te undeside

of yor am is relaxed. Musles ase

movement in only one directin; they a

pull, but they cannot push. So to lowe

your arm, you relax the bices and at the

same time ontract the tices to pull you

arm back to its original sitin.

The liing reqires moe enegy, a

so the bices is the lager and sneof the two musls. Mst carenters an

other workmen who se their ams a lot

develop large and powerful biceps. n al

cases, however, the muscle tat bngs a

appendage closer to he body is mu

sronger than the one that lls i away,

as in the case of the bieps and the ti

ceps. As anoher example, the musles

closing your jaws are much stronger thanhose that open them. Muscles never relax

totally. Even a rest muscles are in a

slight state of contraction, called tone."

Wha makes yor muscles start moving?

Nerves are conneted to each muse nd

receive messages or simuli ransmtte

from your brain via he spnal cord or

someimes direcl from he spinal cor.

The nerves trigge the muscle to contaor to relax. You cntrol the action of vo

untary mucles b our thouhts.

19


22/52

uc o th ody

A ge po ou bodis muscl-

bout one hao ou totlweih.

nvunta muses are set int per

atn b fatr ver wi u ave niet ntr. As f mves trug teigestive trat, r exampe, it appiesressure te was at varus ints. isauses e mues t ntat an reax,reatinga rippingmvement, aed peri-stass, hatkeeps the fmving.

Wen u beme t, te muses ine was b vesses near te surfaef te kin autmata reax. is a re bd t enter te veses,i as mve se t te surfae.

0

Tese atins ep yu . n

ntras, wen yu are , te musesarun te b vesses tigten, nstriting eir size an reuing te amunf b brugt se t te surfae. Ate same tie, te b vesses are puearter bew te surfae.

e mvement f an muse requiresenerg. s mes rm e fs ueat. ese fs are igeste an ten

arrieb

te b t te muse tssue.e fs tat su eneg fr mvina mse me nrma frm sugars an


23/52

starchs hs ar cnvr nt a smlsugar, call glycgn, hat s str n thby Bcausf ths str nrgy n yursystm, yu can run r xs n thr

ways wthut avng t tak n f at thsam tm u rplac th suly latru bcm tr whn yu hav x-haust yur nrgy rsrvs a wastructs n t muscl ls av bul ut a h lvl s yu rst, mst f thswasts ar chang nt carbn an watr, whch ar carr away frm

th muscls by th blWrkng muscls ar rchly sul

wth bl vssls, fr xygn s ncs-sary n th rcss f changng th glycgn nt nrgy hs ar th "rmuscls f th by rhas th bst xaml f a r musl s th art, whchgts a scal suly f bl nrchwth xygn If th xygn suly t mus-s s t , ms ts ry s s , r x, a uqut must b lsn vry fw mnuts

t all bl w g xygnstarv mscls b h bnn

Muscls nt us a hunr rcnf th nrgy hy gnrat In at, nl

abut tntyv rcnt th ngs nrt n k n snt ttally wast, hwvr, fr t ksth bl an tssus warm Whn yu xrcs r avy wrk, yu r unmr at tan yur by can utlz ubcm ht an must cl frm tmt tm

ny by mvmnt nvlvs anymuscls an many nrvs s cmbnactn btn muscls an nrvs truc sr mvmnt s knwnas muscular crnatn Wn vl-ng muscular crnan, n must rstthink abut mvmnt h atht,th muscan, th carntranyn ng muscular sll an crnatnrac fr many hurs, unl thmnts rqur mnmum f thnkng

/an

bcm amst umatc I

Mucular coordination i required or a activitie


24/52

Yo tt Digetive ste

rbaly eat tree meals a ay,ea meal at a regar me our ges-tve syste s ajste t ts see Ifyo mss a meal, yu ave nger "ansr yr stma "grwls ese sgnalstell tat r stma s emty anre fr mre f r stma s testrge sa were f s el n reserveefre eng fe nt yor lng lwer -gestve trat I strete t nt ne tb, etve trat wl exten t at

n ens en e o r mou a egn ew e f s xe wt sava tat mesfr tree s f ns nse r e lva nans te eymen t bras n te strs n

eat n sr Enymesa ex stes

Wtt tem, gesn f lnt r

e mst, ewe mass of f nyr mut s ale a ls Wen t sswallweyr tnge els nt nln mvng te f between te teet btals n sqeeg n te rattebls mvs n esgs, e eleag yr stm It s stre n estma ntl e small nestne, te nextportn f te gestve trat, s reay treeve it ease y ave ts stragearea, te meals y eat an rve rgestve trat t wrk fr severa urs

Sme gesn f f als rs nte st e sts wlls rlle wt gestve glansmre tan0000 f tem ey nstantl r tesertns nt te ass, w ssowly urne by te stma mslesese seretns ntan yrolr ere are als tw gestve enmesthat at on prtens, breaking tem wninto smpler sbstanes noter enmen te stma es starts a weak ges-tve aton n sme fats

s re n te stoma s amus that lubrates te fo an, at tesame tme, makes a rtetve lnng tatrevents te a an te gestve jes

from eatng nt te stmah wall eglans n yr stma r frm ne tt qarts f gestve jes nt sma eve ay

B h me e o rea o movento te small ntestne, t s a semlqreferre t s yme, w mens "jeJe frm te neary anreas s mxewt te f as t eners te smal ntes-

tne e anret e nns treeve n t n ns

,


25/52

Sa ivary glands-produce- 1

sala,' wh begins digestion.

Diaphragm (not partof digestive syste)separates dige$tiver

an s from cest

avity.

pagus-passageway forfood leas to stomach.

Liver-produces bie

Mouth teeth an onureceivean chop fo mx salva wthfod, push fo own troat

Stomac-receives andstores foo preparesfod for dgeston someigestion occurs).

Pancras not shown lisbehin stomac)-proucesseeral digestiv juices foruse in small ntestin.

Gall blader-stores bi

wh ch is necessary for

dgestion offats nd

Rectum-stores wastesunti l el iinated.

c mptes nto smallintestne

Smlinti -rdu e

sevral digtjuice, dige n borb

ost

af h d.

ar

i cvs

ngl f o mxd

wi wter, b

the wate.


26/52

staes, an fats, hangingthem t muh

smle substances. Fat igestin s cmletely suessful nly hen ble s resent, heve. This yellis gee ui

omes into the mall intestine from thegall blae, here it i stre aer beig

pruce in the liverThe liver serves priarily as a torge

ae f suga, which it emve fro thbl an the retu t the bod itimes of ee. It i estimted tht t ymmet but twety percent o thebdy' bl supply i i the liver.

Digetive ezyme are ls dded rothe small itestie. These ezyme cmplete the digeti f rotein, bre dwvariu sgar to the ilet sugar, dfurther diget fs.

Lped back d frth thrugh the dme, the sall itestie my be a uch

as tenty feet lng. The greatest amuntof gestin an abst f f takespae hile the f is taveling tughthe small intestie.

Muscuar cntractis f the wall f thell iteste ve the fod mass alnglwly. Sluggishly, it aes its way beteen an amng the ma iy, ngerlik prjectis calle villi These prectins increase the ttal sufae aea thell itetie by any, y ties. Thedgested d are bsred it the ltht w through sall lod vesels

clled cillrie. The cpillarie e cleto the urface i te villi The igetedd i th crried by t bloo to ll

rt o th dyBy th tie the fd etrs he arge

itetie, but ll tht remi i smeidigtile debris ixed with water. sthe ve o, much of thi water isreasrbed it the system thrugh thelarge itetie's walls. The terials thateetualy ass out f the bdy are mailyli. They are waste reai f fd thatwa eate e r tw y erlier

In th e smal l intestine, digested food is absor bed by

tn, n erlke pr ojectons cal led vll, wh c co ntan

many capares.


27/52

Lus-Yo Beat f LieYou cn survive for several ays with-

out waer an for perhaps as long as aonth without foo. But you annot liveuch lnger than ve or six minutes wth-out oxygen.

ou get the oxygen fro the air youbeathe. At the same tme, y get riof carbon ioxie, a waste gas. hs i-ptant exchange f gases taes plae nyr lungs

ete t tg ab tan ntne wen y are asleepat alost the same rte as when you areawae. u nale n exhale bt eg-teen ties ever mutesome eoeore, sme less. In this peio you taein about eight quats of ar. You breatheore slowly when you are resting anfaster when yo ae wring, exesng,or excte. ou ate of breathng anges

5


28/52

w yur nrease use f xygen. Yuwll als breahe re es per mnuea gh aues, where e ar s "hn-ner an nans less xygen han t des

a sea level.Yu nale, r ake n ar, when ees, r hra, avy bees argeras a resul f w ans ha happe ae sae me. Te aphrag, a n,srng shee f usle, nras. The a-phrag exends arss he base f yurhes an s eshaped. When -ras, aens pushng wnwar.

he same e, her usles pull he rbsuwar. These ans nrease e sze fyur hes avy. Beause f s nreasedspae, ar ves n he lungs fr ut-se te bdy. o soner s s ne hahe usles relax. Ths dereases the spacen he hes avy an fres he ar ouf he lungs.

he cnrl enter fr yur breahg

s yur branspecally, he lwer partf he bran, r edulla. prto of tsells are sensve o the aun f car-bn xe n yur bl. When carbndoxe nacts hese cells, ey sed upulses a otra he uscles of youraprag an thse ha l you S, oddly enough, whle we reahe o geoxyge, t s the carb oxde tha setshe ato to. Even rpid breahgs rugh aou ecause yur syste arryng a exess of carb oxde, caus-ng re pulses be sen fr te crlenter n he bran.

cog a r ae og caels of your osrls. goe trough aewrk of rs arse ars and hen aarpe of exreely ne ars. They lerou any sl parles ha gh be n thear. These ar haers als have slnngs a help clle us r oher

6

Rib movedown and indiaphram up;hest cavitontract; arforce outof lun

arcle. Te lngs have ay salllood vessels close o he surface, helpngto war the ar efre reaches he lung

he phax, the area a he ak fhe throat, the cog a hares for aho dae he sae path whh fodraves on s way e stmah. If yuhold wallow food wle alkg, teood oees ges sck he eraneo the wdppe and you wll cough adhke unl dsldges. Ths des nusually happe, because as you swallw, uca a cae h go eto close o the etrace to te wpeo trahea

Ts pathway beween yur muh anyour respraoy tract s wha allows you

o reahe through your uh rbreahe hrugh he muh s n lere;


29/52

trutu o Lung

bonchiole andcluster o f airsacs, or alveoli

or is i war as i is wh i goshrough h asal chabrs. ak sveralbras of air hrough your ouh o acool ay ad copar e wih hosebread hrough your ose. he ier-ec is very oiceabl.

h wipip, or rachea, is a largeuscular ub ha is sie by rigs ofcarilage. I lads fro your ck o yourches, wer i divides io wo brocialtubes, oe o eac lug. I your eck, atte ve op of e widpipe, s t laryx,or voice box. You alk or ake oise byakig air go over t vocal cors iyour laryx.

Isie each lug, te brocial tubesivie agai ad agai io a ewor

of tubes calle brocioles. Each edsevetually i a tiny, ve iwalled air

airair

air aor alveolus

sac, or alvolus, which coais urouscapillaris. Eac ug cosiss of lirallyhousas of ee lile sacs. I is i teselil sacs ha te bloo releases carbodioxi a akes o oxyg.

Bloo coig into e lugs is ark re.I is pumpe i fro e earby art.his bloo coais vry ile oxyge buthas a large amou of carbo dioxe.

Re bloo cels ave te ability o ab-sorb large amounts of oxyge At te samie at te re bloo cels are takig ona ew supply of oxyge i te lugs, tebloo is releasig e carbo ioxie thas bee carryig. is cages e colorof your blo from dark red to brigt re.La it n, t bl is a

by veins bak t te ear ad is pumpefro tere to all pars of e boy.

inoxgen


30/52

8

Your Bdy's B ld Pmp

artr-

red

ven-blu

The heart is abt the size f a lenhedst. This prtant rgan is late be-

t

een the lungs, alst in tec n

fthe hest vity. t is tipped slightly, sthat its tapered lwer end pints se-what to the left.

heat is the st harwkingsle in yur by. t began beatingat ve nts efre y wer brn.t beats fr sixty t eighty ties eahinte. n this brief perd, the entire

bld supply f yr bdyfr three ve arspasses thrgh yur heart,having ade ne plete tip thrghyr bdy. f y exerise, yr heartbeats faster, and the bld ves rerapidly.

The heart is a sular furhaberedpp. t nsists f a right arie and ven-trie and a le arile an ventrile. Theigt sie f e heart is separated fr tee side by a al f usle aled te se-. Te auies are inalled, and teirriary jb is t reeive bl. he ven-res ae tikae, and tey upbld t all ars he by.

Al bld vessels evenually lead hehear and hen aay frm he eat. Thesebld vessels, lus he heart, make uthe irulary sysem. This vial sysem isomse o tw major ivisionsthe systemi irulatin and e ulmonary irulain. The systemi irulain is maeu all bld vessels ud in he body,xe hs n te luns. e umnairulatin is made u f all bl vesselsund in the lungs and se leading tnd frm hem. I is much srter han

the sysemi ian.

Bld rm he sysemi irulain eners he righ aurile hrugh majr


31/52

or

rur

to r o

veins. At the pint where these veins en-ter the auricle, there are valves. hese ne-

way valves allw bld t w int theauricle but nt back int the veins. Bldentering the right auricle is a dark redclr because it des nt cntain muchxygen Hever, ths bld des cn-tan a geat deal f carbn dixide.

s te aurce ctracts, the bd mvethrugh anther neway valve that sep-arates the aurice frm the ventrce. hen,

as the ventricle cntracts, t clses the valvecnnecting the tw chambes an frcesthe bd thrugh a large b vesse

1 Arcl rcivi l2. Vetrcls p pg l

Aices u b Vri rcv

called the pumnary arter. here is an-ther neway valv where ths aery jins

the ventricle. s valve prevent te blfrm wing back nt the ventricle.he bld crcuates thrugh the lungs,

lsing the carbn xe and acqung arich suply f xygen. his xygenicbld returns t te heart and enters tee aurce. rm tere, t w dw the le ventrice, ten is pumped ut anthrugh the rest the by.

he vens tat enter the e auceals cntan neay vaves, and tee sa arge, nea ave hat cnnects t

29


32/52

cava

ont o Adult t

ro _ to had ck

r shodr ad a

e aure th the e vetre. here isather ea vave hee the ates te eft vetie

e heat is st se but nt the sae thikess thruhut. he us-es f the ventries ae uh thikerthan thse f the auries he ventrilesust pup the bl thruhut the by,

s the nee th reater usle poer.he heart stant eeives a pupsu bl. e t aries k nearl phase, as the tw ventries. Whenboth auies are led, the weakl con-tra, ast at the sae ti. he bloves int eah ventrie ad s thesehbers. hen the entriles ntrat, al-ot i uis. A heart tratin beins

he riht auie a the spreas arssa e at the btt f the en-trles Whe th tati s pete,

0

he heart ests fr a frat f a sea the rpeats the e, ver an ver.

What akes u heart beat? he r eter i the het is ae te pa-

aker. t is a kt f nerve tissue at the riht ae. Waves, r puses setut fr the paeaker ause the heatuse t ntrat rhthay. he ratef yur heartbeat is hae by t nervs.One of these neres is the vagus. Ipusesfr this nere ake yur heart beatre slwy. Messaes fr ather nerveake yur heart beat re rapi hese

erves futin autatiaDtrs listen t u heart ith a i-

struent ae a stethspe he heart ny the beat but as the si fthe vaves beteen the auies ve-tries an the vave in the are bvesses If these vaves ae nt s pete, ts i te u that u havea uur.

artry v capa


33/52

g artr lavng t l vntrls all t arta. Nar ts as ar tsmall rans tat supply t art mus-l tslf t xygnr bl. Just ut-

s t art, t ara vs nt trlarg brans, w v agan anagan as t ntwrk f vssls spras tth varous parts of t boy.

e arta s abut an n n amtr.It s th largst bl vessl n yur by.The smallest of the arteres, t artrls,hav abut te same ametr as a arnyur ead. But t wallsf vn tese

small artrles, as wll as ts f tlargr artrs, nsst partly f muslsTy an ontrat t sut r ru tamunt of bld ng trug tm,r they an rlax an strt t all tevssel to arry largr amunts f bl.rterioles bran t frm apllars.

vast ntrk f aplars m-pltly las t tssus f t by, pus

ng amng t lls. n t als tapllars ar nly a sngl l t tlqu prtn f t ld an u t tssues ntrmnl r. F matras

sslv n t bl an xygn arrby t r bl lls ar xang rarbn x an t arus astsfrm t lls.

Caplars jn t artrls t tvery small vns, r vnuls. Vnuls m-bn t frm largr an stll largr vns,arryng blo bak t t art.

Capllars ar te smallst ft l

vssls. Ea apllarys nly abut 1 /250of an inch in diameter, but most of the

bl vessls n yur by ar apllars

-a ttal f abut 60,000 ms f ts

mnutevssls Ifty rmnnt

n tub, t ul av a amtr 60

tms ratr tan t arta. smallr t bl vssl, t mr

slly t bl s tru t.


34/52

Cooio

o ood

iid 55 rct(water ad dsovdatias)

sods 45 rct(d ad whit oode, att

d ood s

Vario kid owhi ood ce

Red ood e s he oo

ptees

A white ood eappoaes a actei

Th whi ood ce egs te ai. The ei s desoyed

many small vessels carryesameuaniy

of blood as do fewer large vessels, bu iis sread over a muc greaer are is

like e waer froma garden ose, spread-ing over sidewalkor a pato: I will sill

move bu a auc

slower speedf you scrac your skin, you will cu

roug many caillaies, bu e bloodonly ooes from te scrac f yu cudeeper and appen o cu roug anarerole or even a larger arery, e bloodcmes ut fasterusually in spurts cor-

respndng o your eartbeat f you cuthrough a venue or a ven, te boodws frm te wound smoly

3

Blood consiss mainly of a yellowisuid called plasma, wic is bou ninypercen waer n e plasa are e red

blood cells, wie blood cells, plaeles,and various sals, foods, and oer sub-sances, in soluion Mos abundan ofe solid maerials are e red bood cells,sll discs re concve, or olowed,on b sideslie backobac saucersRed blood cells are only bou /500 ofan inch in diameer, and you ave twenyo wenyve rillion of ese iny cells in

your body f ey were laid end to end,e ininewuldcircle - earaburee times


35/52


36/52

ross Sction o Kidny

roto

a

r ur

Show ar t az c lar atu cry

t ury thl h trrucur cda hr

Kidneys-our Bdy's F ltratn Pant

Wastes of seeal kinds ae elmnaed

by the body. Cabon dode s easedfrom e bood and eaed fom h lngsin beahng. Sod, ndigesible maeasass rough and o of he digesitac. Lud wass, conaining dssoedsas, are ed frm he bood as asses hog h kdneys. hy a eneimnated fom e body as ne.

he kidneys a wo beasapd gans, eac abt z f a sa s.ey are ocaed a he back of e boy,one on ac de of e pa o, aboe p.

nsi f a kidey i cops fan laye ae c a aine ay, e d. Each ay maze of ma ars vins caaand osand and hands of nytbes. s smad a f a h b

n a snge k e pcd tey wod meas o foy es. s

34

iny bes evenally cec w

age e, wic empts nto an scsac, te bladde. Th baddr ods te

ne n is eminaed fm h by.A age ae bings bood ino ac kd-

ney, and a age en caies e edbo away.

ay eneng kny dvdesn ay a bd o ar, and ly pe a okk a agld kno f ed ya. angd ocn f apla caed agomeuls, and is ed nsie a inystct ad aBwa' p. T

a l f kd. a B p y y b d y aplae. T er uu

ephron. As te bld passs trug

these tiny mazes, it becomes purifed- ,eed fmy we, meof which ar very poisonous o th body.


37/52

Bri, Nervesor Cnicatin Sys.m

f yo cold remove all the parts ofyor body except the nervos system, yo

wold still see the shape of yor body asa gaelike nework of tiny neve cellsand threadlike bers leading from themere and there wold be knotlike swell-ings, or ganglia, where many nerve cellsare assembled The nerves connect withthe spinal cord, wich in t connectswit the brain The brain lls the cranimof yor skll and is itself one arge mass of

nerve cells and gangliaor nervos system receives sonds,sights, smells, and other physical andchemical stimli from the world arondyo and from inside yor own body Theseimplses are passed along nerve bersThe speed at which these messages travelvaries with the sie of the nerve n largenerves, messages move s rapidly as 5feet per secod n small nees they movemore slowly

The basic nit of the nervos system isa nerve cell, or neron typical nervecell consists of a central body with root-like extensions called dendrites and axonsThere are several branched dendrites,long or short, depending on the kind ofnerve cell t s the dendrite that receivesthe essage There is saly only one

axo, and it, too, is branched at the endThe axon is the part of the nerve cell thattransmits the message Nerve cells almostconnect with each other The end of anaxon from one nerve cell will almost tochthe end o a dendrite rom another nervecell This extremely small space betweenthe ends of an axon and dendrite is calleda synapse

Some axons and dendrites are vesort; oters may be several feet long

.

' t -''


38/52

hey may be bound together lie the smallwires n a large ale. These form largenerves, whih are distintly white in oor.olletions of nervel bodis, in on-

trast, ae raishYour nerous system onsists of yourbrain and spina ord ps a hug numberf ther nerves The brain an spina rfr the entra nervus sste.

Th spina r starts fr the ase fth brain an extens ast the engthf the bakbne, prtete b the bnvertebrae. The enter f the spina r isra, nsistin f nerve el bies. Theutsie is white, ae up f the enritesan axns f the el bies The spinar is the enter fr reex atinsthatis, iret an ieiate reatins, aswhen u tuh sethin ht an jerkbak instant, withut thught.

Reex atins ur when ipusesfr sens nerves arrive at the spinalr n are transitte irety t ashrt nerve that nnets t a tr nerve.A essae then ves alng the axn fthe tr nerve t the usle that brings

Whe yo to a hot oet,eves the s se essage to e spa o.he pa od eateyes a essage to the ep

ce, whh the otactscasg the had to jek ak.e esage aso taves to hea ad egstes as pa

about the needed ation, suh as jringba. This happens with great sped, andth brain s not involvd. The essag desntinue an the spina r t the brain,

whra

emr rer is made t r-mnd u nt t tuh an ht thins inthe uture.

What sets huan beings apart r ather anias is their brain. Mst f thesystes in the huan byiruatry,respiratry, an thersare uh ikethe sae sstes in gs, ats, an theraals. Even the vital spinal r an

ther parts f the nervus yste reseblethse f lwer animas. But the huanbrain is prprtinatey larger an betterevelpe, partiularly thse pars havingt with thinking n reeberingrinteligene. It is this ple ass fnerve issue, weighing abut three pun,that akes yu s very ierent fr alther animals.

Yur brain nsists f severa bsiparts. The eula is the enarg exten-sin f th spinal r at the very base fthe brain It ntrls any iprtant by


39/52

cerebum (argest portion of bai)

att, u a bratn, artbat,

an tr nlunta, rxtyp atn.Ab t mulla are te mbran an

pn. Ty ntrl crtan by m-

mnt an at a a rlay ntr. Next

t npaln. One prtn f t ru-

lat by tmprature unr trst

and sme f te baic emtins such a

anr and fear.

Laed undeeath and at the rear o

te crebrum is te cerebellum r "littl

bran. It is antr prmarily rx cntr,

lpin mainly t rnat te mve-

ments f mucls If t is not funtinin

rerl mvement beme jerk, walk

diencephalon

n untay, an tr a nral

trmbn. T rbllum al lp t

mantan balan, rn pul frm

t rular canals n t ars.

T lart prtn f t bran t

rebrum, acuntn fr trfurt r

mr f t bra' tta t. T

te rat dmap, wrnkl an

r ma tat cup mt f t

bn craium. I is divided int right an

le al, r mpr, an a f

te al a fur lb wt p

funtn. Of t ruy tn blln l

cmrin t nru tem, abut afare fun n te rbrum.

37


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e eebum s te pat te bant u u tg an ea-snng t s as te ente mem spee an te senses sgt,

erng, se, taste an tu mpusesm te eebrum as g t te muses te ams egs, nek, ae, nge ante pas en te ggng u t-te te s nte b ts pat o teuan bain nteresting, te ght haff e eebum onts movements onte e se f the b, we te ea nts

m m nts

on te rht sie

f te by.ese ae the ve simpest funtionsf te bran whh s ative twentfouours a aeven hen u ae aseep.ts mpuses, ae bain waves an bemeasue Thei patte is as stinctvef ea ndua as ae the ngerpnts.

ight do aotroet ideo ody

o ractror gt do dy

Cnnete t te ban ae tweve pas ana nees Te are the pathwasbeteen te bain and your senses fe easme, sight, heaing, taste, an

baanean hep to onro the move-ment f te ees an the vaius muses te ae On the tenth ana nerve, vagus, ges t the interna organs ofthe boy. t ontos gestion, heartbeat,breathing, an simiar funtonsa auto-maticay, without o having o thinkabut them.

The vagus nere merges with te auto-

nomic nevous sysem. The autonomisystem, nees that ie otside the spinao, functions utomatcay. t has con- e te se f b vesses the ac-tion of the musces in the digestve tat,the seetions of the igestive an sweatgands, the heat rate, and ther ativities.


41/52

t

vitros umooptc (a a yi

+ ia tat s ti avi)

ovig)

(olorporto

sera -

(otr ay)

eeg, Heg, Oe ees

our eyes are speca sense organs.Rays of light that enter these two wn-dows fal on te retna, the very ght-senstve tssue that lnes the back of eacheyeba. he ght stmuates the endngsof nerves found wthn the retna. hesenerves lead decty to the bran, wherethe mpulses are transated no sght.

he senstve retna conssts of twotes ne cesrds nd cneshere are more tan 00 mon rods neach retna, and about 8 mon cones.Cones enabe us to see coor and functon

only n brght ght he rods are senstve to smaller amounts of gh than are

the cones. os functon best n dm ght and enabe us to see objects as back orwhte. ods are found mosty around theedgs of the retna.

he fovea, a sa area n te cener fte rena, contans ony cones coseypacke hs s te part f the eye thatprovds good vsn for seeng coor dfor mang t ne deas.

Bth rds and cnes are absent n asmal ova area just ocenter at the backof eac eye, where the bers of te otcnerve are ocated. hs s the optc dsc

or "bnd spot, where no vson s regstered at a

39


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rgeduy vwhen lookig at

.

t

1

-

e bjec -

(ag e c a

negedbu vn

nv x e

ous oeted

when looking atI

.

f

-

-

stn bets(u nto en

ccav le

ou rreed

The tic nee from each eye cn-nects direcy t the brain. erve bersfrm the le alf f each eye t thele side f the brain; thse frm the rihthal f each eye t the brain's riht side.ecause o thi rsin er f th ptinee bers, each half f the brain re

0

Ac c mmodat ion-Abi lty f Le ns o Ch ange Sh ape

dagh

en hck

he ookng nto you eye.

cis half a pictur frm ach ey. isenables us t perceie dept r distance.Our ys an thus disinuis heiht,width, and dth and can see three-dimensinally.

ule attahed t eah eyall er-mt yu to tu yur eyes t he rigt or


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le an up or own. Eyels prove protectve covers for your eyes, wc arekept most by secretons from te tearglans an are "swept evry few seconsby an nvoluntary blnk.

usles also control te sape f teles of te ee so tat t focuse automat

n t. es ntl te s, w te ertn f te eye. e openn n t e l. e penng ln

n r rgt lgt lets n r lss t. e ppl appears ast k center of te rs.

e sense o eang s also losel asscate wt te bran. ouns are pouce by vbratons n te ar. Tsewtn te range of our earng are fo lw s 6 u to 0,000 or even 0,0vbrtons per secon. e rnge o e

ng vares wt erent peple. ome anmals cannt ear as well as uman bens oters can etect souns at a lowe oreven a ger ptc. "lent og wstes,or example, prue souns tat are oog or us to ear, but ogs can ear tman can be trane to respon.

ear onssts o tree majr at.e uter ear, one n eac sde f e

e, s mae mostly of cartlage. t srealy te least mprtant part for atale, servn only to elp rect esu waves nt te ear. ome anan tu ter ers to k up souns erety. We ave to turn ur eas t ts. Als part f te outer ear s a stcanl lne wt skn. A tn membranee s late a te e tunelape canal. Wen oun veste te earrum, t vbrates at trsam requen.

e vbratns o te arrum epce up by te tree bon tat m l . ese e te mmer anvl, an strrup, wc g also byte atn names of malleus, ncus, nstapes. ee small bones, arane acan, transmt te sun vbratons to

te cclea, a cole or spraed, ule camer f te nner ear.


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The cochla cntains numerous cllstht e in hirlike structures. Thes har

cells re nnectd t enings of the aud-onee tt transmits impulss dirctly

o he rain n the rain, the vibrationsare trnste int the souns we hear.

The midl ear is conncted irctly tthe trot by th ustachan tub. hmakes t pssib to equaliz theprssur

on eac side of he eardrum, which wuldotheis be rupturd whn you go sud-

enly fro on altitu to another. In anairplane, r evn in an lvatr thatiss you rapidly upward or downward,you swallw t n your ars" and r th sft an aus y

the dirnc prssur n th two sdsof the ardru. T ustacan tub sclosd xcpt whn yu swallow r yawn.

Also locatd n th innr ear ar thr

smicircular canals and tw sall ouch-esattached tothm. Thy have noting t

42

euacha b(pe n he ra

adi

cochea

d with haing, but thy do control bal-anc. l f the canals ar lled wit auid. Th tw pouches cntain vry smallstonlik bodis call otoliths and are

als lld with uid. Movment of thhed or boy causes moton the to-lths and of he ud in the emircular

anals. Nrvs ar stiulatd and mes-sags ar snt t t bran, whi hnrcognizes the in of movement maby th bdy

Athr iportant sns s that ftast. In adition to helping to rsunds, th tngu is th nr f tast.Th tongu has about 3, tast bus.hs n n as ngu pup dirnt astes. Swet, sur, bittr, andsalt ar th fur basc tasts.

Tast buds at th rar f th tonguare mre sensitive to bter ates; thse

at the front, t weet tastes. Saly tastesare registered alng the frnt edges on


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s f n; s ss ng s.

s vy n s. n n s sn, n

s se js . ses s v e f t f nk. As nk s see n n s s n ex.

In n s bs ses, spy n n pt "sngf. If y se y ys n ynse y v y n snsn n nn f n

f gven s n ps s xe s n v y. f y n y ns y ne y. On y sn f y nk y e ng.

Cll tht dtcll lcatdi th r th

n cvt

sns f s s in a - s bve n f g e nss Ony y sns f s fs s g, e

ne be se. A nt -en f the ve, th smbes ess n ss nb. Lgns f te fs e qe be-fe h n be eete.

an, eat, c, sse, tctese snss n e skin. eysenses f "fee. Ea typ f eatn ss by n neve enngs fnin t nbes n e skn. On a sal f skn, f ex, y n f e f pn n n pe bt n n.Ae sp gves e senat f panb nt t.

es senses a xey ntto the rotectin f yu by. hey telly en yv n n s bj n s ty vn ses ns. As ey n-

b fe gs jts tvng s .

tuch

Show ege a ve nsoy veudl ad whr they e oted inth ki


46/52

The Enoine yseheia nt

la

vaal e

i la ofLara(lcted p cra

e edcrine ytem i cmpe f

a nuber f ma, peciagand cated

invariu part f te bdy. ey ep t

cntrl by activitie and functin by aderet metd tan tat f tenervu

syte. Nee are cnnected neto at

er, and meage are ent alng tem a

toug tey were wire. Nee goe

immediate ad fat-vig actions, uc

a te ctractn f amuce. e endo

cine gland cntrl actiitie ttare geerally lwer but ave a lnger, or me

s nnt,t on thbdy. Tno s ndicby the rlas ofsp-ci

cmcin bd.Tscmi-calsar caldhoones.

Hns dtine yur fgw nd dvlpment. They lp cn yo bar and hav u tdw pnty and emoon.

e ater encine gan t puita, a ma gan ate at e t rn. A a te gan

, in fat, ttae t te brain. evramn are pue by te pitutan, an tey ae f uc via mprtanc ta yu u nt urve n ift gan re remve

One rmne frm te pitutay cn-tr te grt and functinng f teyri an adrenal gand, a in teenine ytem Anter etermine

yur grt patte. muc f tirne pruce giant; t itte pr-duce drf. An exce in ater ife mayreut n big feet and and, a "antejaw, an an exceptinaly ng ne andbig ear In adut, rmne fr tepituitary aect te ecretin f male andfemae ex ne, and tey ctrl teamunt f atr tredin te dy, wichaect te bld preure.

e tyrid gland i lcated in thetrat, jut bve te vice bx, r arynx.e tyrid i eties referred to ate "paceetter becaue its rmne ctrl te baic procees f te bdy. tepecially aect growt patte. il-dre wit too litte of thi oroe become metally ad ysically retarded.ey are called cretins. dults wit a de-

ciency f te rmne becoe fat, we,nervu, an ften etally sluggish.


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If an excess of the hormoe i pro-duced, people become thin and "op-

eyed" that is, they have otuding eyeballs. owadays the rodution o the

hormone is oen slowed down y giingdrugs rather than by an oeation to e

c rgland's hormone

prc ll lt llr rppl.

9

74 m

8

44 r

7

1

6

1 . 8 3 r

. 6 1 mr

oe t o the tyoid gland, the eedy i te at.

Just behin the hyroi glnd are two

ais o mall, ellowih, easied glands,

the arathoid. eoe they wee eogied, they wee soetime emovedalong with otio of the thoid ingoite oeatins. Death alwas esulted.The homone oued y these glandsis neessay fo the oe funtioing ofthe neous sytem.

t the to o eh idney is an esied aeal glad. t onsists of an inner

otion, o mella, and an outer laye,o otex.

The medulla rodues the est ownof all the homoesadrenalin. ometimes called the emegen" homone,it auses the liver to elease more sgarinto the blood, ths maing ossible theexta surt of energy needed either orght o for ight. drenalin also maes

the blood vessels of volunta muslesdilate so that they are ihly sulied withblood. hen adrenali had been ouedinto the system, almost suerhuman featsare ossibleat least, erfomanes thatfar exeed what ersons an normally d.

The outer layer of the adenal glandsyields several other hormones. They helpto ontol the

rat

at whih sgar is usedin the body. They inuene, too, the rateat whh salts are exreted by the idneysand govern seondary sexua haratersts, suh as the growth of the beard .

Within the anreas are found the islands of Langehans, grous of endoine

ells. Their hormone s nsuln essentalfor the body's roer use of sugar. ithout nsulin, the sugar n the bloodsteams not sed by the cells This is te disease

alled diabetes whih fortunate anusually be ontroled b taig isuin

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.

More f a Kind

Every lving thing in this wrld is apa-be f reprduing its wn ind. Repr-

ductin is literally a law f life. Withutreproductin, lants and animals wudnt exist.

Al ants and animals are psedf living ells. The mst fequent ay freroducing ne iving els is simply by

ell divisn. A singe cell undrgs aseries omliatd hanges nd thndivides, forming two cells. It ctualy mu-

tilies by diidin. Eah nw sywill be idntal t its pan l, xcptthat it will be smaller-about haf th iz

the riginal ell. Reprduing by dvi ion is nwn as asexul rprdutin

Onecled pants nd animls due by asexual rduin. Under d

grwing n ns, sme btri rapable f dividing ut eery ftnminutes. As singl ateriu dids,it prdus tw ne els. Eah f thsedvdes, produing fur new ls. Thefur els diid t prdue eight nells. Ater just twnty suh disn, -urring n abut hurs, there will ever a half millin new bateri els.

Asexul rprdutin us at varyingrates ial living things. Most of the cells

i yur dy diide nstantly as yugw and as wut r damaged partsae relaced These ells rerdue the-selves in exat detail as they maintain thehealth and upkeep of the body.

Huans, ike mst f te familir an-mals, annt prdue re f their nnd by asexual reprdutin. Fr them,sexul reprdutin must ur.

In sexual reprodution, te mae con-

tibutes rerdutve ell alled these. he female's share is rvided by

6

Male

Reproductive

System

fertl izaton (egg

and spem unte)

pens-

to uteru

Female

Reprodctive

Sysemsperm

singld gg, r u Bt thspr el nd th eg ar inmpltes, pl f iing y thsles frnl a shrt time hey b mplts when thy are united. Tis unitin fsper and egg is nwn as fertilizatin.Th frtilized egg thn diids again andain, y sipe e disin (asxua re-prdutin), prdung a han eingOnly a fertilized egg is aabe f gringint a n indiidual.

In the hman rrodction syste,

the ar speca organs ht pouce thesperm and egg. These organs are called


49/52

gonads. Theale gonads, or testes, pro-

duce the sper. The feale gonads, or

varies, roduc the eggs. When an egg

isprue and then eased by an vary,

it rave dwn a a tube called theiduct. It is inthe oviduct tha thesper

and eggunite t frmaertlizedegg. The

fertilize eg then travel t the uterus.

Bth he vidct and e utrus are part

f he eale reprductive sste. It is

i he uerutha thefetilize egg grws

anddevelps int anw life iabut nine

nths' tie.

The develping ferte egg is calledan e. t rst, the ebry appears

e

otho

thr

Gowt and

Development

f a Bab

iothod

t be nthing re than a as f grwingcells. As develpent cninues, the cellass begins t take shape, until, at abutthree nths, it is asily regnie a a

tiny huan being, r feu. he fets cn-tinues t grw, kig e and e likea huan. Finally it eerges fr heuterus, and a baby is b. uring inienth perid f gwth, f fe

tilized egg newb baby, it inraesits weight six bilin times

In the nucleus eah cel ae funany small, slender, dark thrad e

chrses. There are frtysx hr-ses in alst all huan cells. ebld cells d nt have any because heyd nt have a nucleus. Egg and spemcells are dierent in that they are inm-plete cels. Each has nly twentyteechrses within its nueus. hn a sper unites with an eg0, restres echrse ur t frtysix, thuaking it a cplee cell.

Each chrmsme i ade up f ssaller units called gen. t takes sevraun enes t ake up ust a ingle


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al u cmsmes a ees cme m u ae a alfm u mhe

roosoe. Every boy ell tat as anles onans tousans of genes It st genes that elp to eterine yourlooks an other iniviual arateristis

oug hlren reive alf of teirgenes fro teir fater an alf fro teiroter, tis oes not ean at tey wllave alf o ter fater's features an alfof teir moter's. Ea gene is paire wita maing gene fro te oter parentus tere are two genes for ea trat,not one. Hoever, one of te genes mayoinate the oter

e gene for brown eyes,fr

example,is oinant over te gene for ble eyes.

If yo are browneye, you ig aveone gene for brown eyes a the otergene for blue eyes r it igt be tatbot of your genes are for bown eyes fyou are blueeye, it means tat bot ofyour genes are for blue eyes ou o notave any genes for brow eyes

ll inerited traits are te reslt of aombination or a ixing of gens bot

00 trllion ierent gene ombnationsare pssble s is wy yo ae inee

8

uniquepositively unlike any oter uanbeng ou ave many eaures tat arelike tose of ne or bot parents or toseof your broters and ssters, ut you arenot xactly like anyne else in te worl.

nly one exeption is possble Ien-tial twins, wo are always of the samesex, have te same ineritane Identialtwins are formed hen te egg diviesaer it as unite with a sperm an tenea of tese ells evelops nepenentlyTeir geneti ontent is iential.

rateal twins, however, are no morealike in teir ineritane tan are anybroters or sisters in te family. ey are

forme wen two eggs are proue anea s fertiize by a ierent sper atalost te sae tie. he twns then e-veop togeter rateal twins ay beof te same sex or a male an a feale

Genes o eerine inheite ara-terists owever, a la of proper foo,exerise, an rest an inune growtan personality evelopent How you

are for yorself is just as important as tekin of genes you inerit!

0

u


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Golden EXPLORING ARTH Boks travel f beyond h uais f he

p g. h ed raders o excit n epet in - whethe n hm nd r fot n open ther eyes t te mn facation s the tral

wol ah k n he seres n advntre f the g naur le

or einni sienis h wishe o e eter acqaind th r earh

and s an arels

Golden EXPLORING EARTH Books

FWS, REES, N D A NI N OCANAPHY

RTIS AN AMPHIBINS NA U E HIK S

ROK AD M I N E R LS

R 50 UNIE STATES

T H E HU B

I O S A U

S C I E N C E

HORES

SR

ANIMS

INSE

BIRS

Human Body, The

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