Chapter1Passage1HumanBodyInthispassageyouwilllearn:Classificationoforgansystems2.Structureandfunctionofeachorgansystem3.AssociatedmedicaltermsTounderstandthehumanbodyitisnecessarytounderstandhowitspartsareputtogetherandhowtheyfunction.Thestudyofthebody'sstructureiscalledanatomy;thestudyofthebody'sfunctionisknownasphysiology.Otherstudiesofhumanbodyincludebiology,cytology,embryology,histology,endocrinology,hematology,immunology,psychologyetc.認識人體各部分的組成及其功能，關于認識人體是必需的。研究人體結構的科學叫解剖學；研究人體功能的科學叫生理學。其余研究人體的科學包括生物學、細胞學、胚胎學、組織學、內分泌學、血液學、遺傳學、免疫學、心理學等等。Anatomistsfinditusefultodividethehumanbodyintotensystems,thatis,theskeletalsystem,themuscularsystem,thecirculatorysystem,therespiratorysystem,thedigestivesystem,theurinarysystem,theendocrinesystem,thenervoussystem,thereproductivesystemandtheskin.Theprincipalpartsofeachofthesesystemsaredescribedinthisarticle.解剖學家發現把整個人體分成骨骼、肌肉、循環、呼吸、消化、泌尿、內分泌、神經、生殖系統以及感覺器官的做法是很有幫助的。本文描繪并闡述了各系統的主要部分。Theskeletalsystemismadeofbones,jointsbetweenbones,andcartilage.Itsfunctionistoprovidesupportandprotectionforthesofttissuesandtheorgansofthebodyandtoprovidepointsofattachmentforthemusclesthatmovethebody.Thereare206bonesinthehumanskeleton.Theyhavevariousshapes-long,short,cube-shaped,flat,andirregular.Manyofthelongboneshaveaninteriorspacethatisfilledwithbonemarrow,wherebloodcellsaremade.骨骼系統由骨、關節以及軟骨組成。它對軟組織及人體器官起到支持和保護作用，并牽動骨胳肌，惹起各種運動。人體有206根骨頭。骨形態不一，有長的、短、立方的、扁的及不規則的。很多長骨里有一個內層縫隙，里面充填著骨髓，這即是血細胞的制造場所。Ajointiswherebonesarejoinedtogether.Theconnectioncanbesoclosethatnomovementispossible,asisthecaseintheskull.Otherkindsofjointspermitmovement:eitherbackandforthinoneplane-aswiththehingejointoftheelbow-ormovementaroundasingleaxis-aswiththepivotjointthatpermitstheheadtorotate.Awiderangeofmovementispossiblewhentheball-shapedendofonebonefitsintoasocketattheendofanotherbone,astheydointheshoulderandhipjoints.關節把骨與骨連接起來。顱骨不能夠夠運動，是由于骨與骨之間的連接太親近。但其余的關節可同意活動，如一個平面上的前后屈伸運動，如肘關節；或是繞軸心旋轉運動，如樞軸點同意頭部轉動。若是一根骨的球形尾端插入另一根骨的臼槽里，大輻度的運動（如肩關節、髖關節）即成為可能。Cartilageisamoreflexiblematerialthanbone.Itservesasaprotective,cushioninglayerwherebonescometogether.Italsoconnectstheribstothebreastboneandprovidesastructuralbaseforthenoseandtheexternalear.Aninfant'sskeletonismadeofcartilagethatisgraduallyreplacedbyboneastheinfantgrowsintoanadult.軟骨是一種比一般骨更具韌性的物質。它是骨連接的保護、緩沖層。它把肋骨與胸骨連接起來，也是鼻腔與內耳的結構基礎。一個嬰兒的骨骼就是由軟骨組成，今后不斷生長、1骨化，使嬰兒長大成人。Themuscularsystemallowsthebodytomove,anditscontractionsproduceheat,whichhelpsmaintainaconstantbodytemperature.Striatedmusclescanbeconsciouslycontrolled.Theendsofthesemusclesareattachedtodifferentbonesbyconnectivetissuebandssothatwhenthemusclecontracts,onebonemovesinrelationtotheother.Thismakesitpossibletomovethewholebody,aswhenwalking,ortomovejustonepartofthebody,aswhenbendingafinger.Contractionsoftheheartandsmoothmusclesarenotunderconsciouscontrol.Smoothmusclesarefoundinthewallsoforganssuchasthestomachandtheintestinesandservetomovethecontentsoftheseorgansthroughthebody.肌肉系統使軀體運動，肌肉縮短產生的熱有助于維持一個恒定的體溫。人體能夠有意識地控制條紋肌。結締組織使肌肉尾端附著于不同樣樣的骨面上，所以當肌肉縮短時，兩骨相互湊近而產生運動。這也就使整個人體能夠運動起來，如走路，運動軀體某個部位，如波折手指。心臟縮短和圓滑肌縮短就不是被意識所控制的。器官壁內層的圓滑肌，如胃腸壁的圓滑肌把胃腸中的物質運送到全身。Thecirculatorysystem.Allpartsofthebodymusthavenourishmentandoxygeninordertofunctionandgrow,andtheirwasteproductsmustberemovedbeforetheyaccumulateandpoisonthebody.Thecirculatorysystemdistributesneededmaterialsandremovesunneededones.Itismadeupoftheheart,bloodvessels,andblood,whichtogethermakeupthecardiovascularsystem.Thebloodisalsopartofthebody'sdefensesystem.Ithasantibodiesandwhitebloodcellsthatprotectthebodyagainstforeigninvaders.循環系統：機體的全部部分需要營養物質和氧氣來使之發揮功能和生長，也需要在這些器官所產生的廢物齊聚而危害生命從前將其除掉。循環系統運送適用物質，排泄廢物。心血管系統是循環系統的組成之一；心血管系統包括心臟、血管及血液。血液也是機體防守系統的一個部分，血液中有抗體及白細胞來防范機體碰到外來的侵襲。Theheartisamusclethatisdividedintotwonearlyidenticalhalves:onehalfreceivesbloodfromthelungsandsendsittotherestofthebody,theotherhalfsendsbloodthathastraveledthroughthebodybacktothelungs.Whentheheartmusclecontracts,thebloodisforcedoutintoarteriesandenterssmallcapillaries.Bloodreturnstotheheartthroughveins.心臟是一塊被分為幾乎同樣兩半的肌肉。一半吸取來自肺部的血液，并將血液運送到機體的其余部位，另一半使流經全身的血液回流人肺。心臟縮短時，動脈把全身血液輸送到毛細血管。靜脈輸送血液返回心臟。Alsofunctioningincirculationisthelymphaticsystem.Someofthefluidthatsurroundscellsdoesnotreenterthebloodvesselsdirectly.Thisfluid,calledlymph,returnstotheheartbywayofanothersystemofchannels-thelymphvessels.Lymphnodesalongthesevesselsfilterthefluidbeforeitreenterstheblood.Thespleenisalargelymphaticorganthatfilterstheblood.淋巴系統也是循環系統的一個組成部分。一些細胞周圍的體液不是直接回流入血管通道，這類體液叫淋巴液，它是流經另一個管道系統——淋巴管而回流人心臟。沿淋巴管的淋奉迎將淋巴液過濾，過濾后再回流人血液。脾是一個過濾血液的大淋巴器官。Therespiratorysystemtakesinoxygenfromtheairandexpelscarbondioxideandwatervapor.Airentersthenoseandmouthandtravelsthroughthelarynx,andtrachea.Thetracheadividestoentereachofthetwolungsandthendividesmorethan20timestoformaverylargenumberofsmallairspaces.Oxygenfromtheairentersthebloodthroughcapillariesinthewallsoftheseairspaces,andthebloodreleasecarbondioxideintotheairspacestobeexhaled.呼吸2系統從空氣中攝取氧氣，并將二氧化碳、水蒸氣排出體外?？諝饨洷乔弧⒖谇蝗撕砉?、氣管。氣管分成左右支氣管，各連接左右肺，左右支氣管再分枝20多次，在終端形成大批渺小的肺泡。從空氣攝取的氧氣流經這些肺泡壁內的毛細血管流入血液，血液再經肺泡把釋放出的二氧化碳排出體外。Thedigestivesystemconsistsofatubeextendingfromthemouthtotheanus.Init,foodandfluidsaretakenin,movedthroughthebody,andbrokendownintosmallmoleculesthatareabsorbedintothecirculatorysystem.Thisbreakdown,knownasdigestion,isbothamechanicalandachemicalprocess.消化系統是一個從口腔直到肛門的管道。食品和液體在消化道里被吸收，在腸道里搬動時，被分解成小分子物質后再進入循環系統。這類分解，即消化，是一個機械過程，也是一個化學過程。Foodentersthroughthemouth,wherechewingandsalivastarttobreakitupandmakeiteasiertoswallow.Next,thefoodtravelsdownthroughtheesophagustothestomach.Contractionsofthestomach'smuscularwallcontinuetobreakdownthefoodmechanically,andchemicaldigestioncontinueswhenacidandenzymesaresecretedintothestomachcavity.食品進入口腔里，咀嚼和唾液開始將食品粉碎，使之便于吞咽。接著，食品經食管人胃。胃肌壁的縮短連續機械化地分解食品，而當酸和酶分泌入胃腔時，化學性消化開始。Theliquifiedfoodgraduallypassesintothesmallintestine.Inthefirstpartofthesmallintestine,calledtheduodenum,enzymesfromthepancreasareadded.Theseenzymescompletethechemicalbreakdownofthefood.Thedigestionoffatisaidedbybile,whichismadeintheliverandstoredinthegallbladder.Thesmallintestineofanadultisabout21feet(6.4meters)long.Mostofitslengthisdevotedtoabsorbingthenutrientsreleasedduringthesedigestiveactivities.液體化食品逐漸進入小腸。小腸的初步部分叫十二指腸，胰腺分泌的酶輔助食品消化。這些酶完成食品的化學分解。肝臟分泌的膽汁存儲在膽囊內，膽汁有助于脂肪消化。一個成年人的小腸有21英尺（6.4米）長。小腸的大多數腸段用來吸撤消化過程中釋放的營養物質。Theliquidremainderofthefoodentersthelargeintestine,orcolon,whichisabout12feet(3.7meters)long.Itismorethantwiceaswideasthesmallintestine.Inthelargeintestinemostofthefluidisabsorbed,andtherelativelydryresiduesareexpelled.液狀的節余食品進入大腸，或結腸，它大概有12英尺（3.7米）長。大腸是小腸的兩倍多寬。大多數液體在大腸內被吸取，相對干化的節余物被排出體外。Theurinarysystemmaintainsnormallevelsofwaterandofcertainsmallmoleculessuchassodiumandpotassiuminthebody.Itdoesthisbypassingbloodthroughthekidneys,twoefficientfilteringorgansthatgetridofanyexcessofvariousmoleculesandconservethosemoleculesthatareinshortsupply.泌尿系統保持水分及體內某些小分子物質，如鈉、鉀的正常水平。身體是經過讓’腎過濾血液來做到這一點的。腎是兩個有效的過濾器官，它濾出各種節余的小分子物質，保留那些供應不足的小分子物質。Thefluidthatleavesthekidneys,knownasurine,travelsthroughatubecalledtheuretertothebladder.Thebladderholdstheurineuntilitisvoidedfromthebodythroughanothertube,theurethra.從腎流出的液體，即尿，經過輸尿管人膀胱。膀胱起存儲尿液的作用，直到尿經膀胱另一端的管道排出。Theendocrinesystem.Thetwosystemsthatcontrolbodyactivitiesaretheendocrinesystemandthenervoussystem.Theformerexertsitscontrolbymeansofchemicalmessengerscalled3hormones.Hormonesareproducedbyavarietyofendocrineglands,whichreleasethehormonesdirectlyintothebloodstream.內分泌系統。內分泌和神經是調控機體活動的兩個系統，前者依靠其化學信使——激素發揮作用。激素是由各種內分泌腺系統造，并直接被釋放入血流Amajorglandisthepituitary,whichislocatedunderthebraininthemiddleofthehead.Itproducesatleasteighthormones,whichaffectgrowth,kidneyfunction,anddevelopmentofthesexorgans.Becausesomeofthepituitary'shormonesstimulateotherglandstoproducetheirownhormones,thepituitarycalledthemastergland.腦垂體是一個主要腺體，它位于頭中部腦下方。它最少分泌八種激素，這些激素對人體生長、肝功能及性器官發育有影響。由于腦垂體分泌的一些激素促使其余腺體分泌激素，所以腦垂體是主要腺體。Anothergland,thethyroid,islocatedbetweenthecollarbones.Itshormonecontrolstherateofthebody'smetabolism.Thesexorgans(ovariesendtestes)makethesexcellsandalsomakehormonesthatcontrolcertaincharacteristicsofmalesandfemales.Locatedontopofeachkidneyistheadrenalgland,whichproducescortisoneandadrenaline.Thepancreasproducesnotonlydigestiveenzymesbutalso3insulinandglucagon,whichcontrolthebody'suseofsugarandstarches.另一個腺體，甲狀腺，位于鎖骨之間。甲狀腺激素調控著機體新陳代謝的速度。性器官（卵巢、睪丸）分泌性細胞和性激素，這些激素控制著男性和女性的某些特色。每邊腎上方是腎上腺，它分泌可的松和腎上腺激素。胰腺不單分泌消化酶，而且分泌胰島素和高血糖素，這兩種激素控制機體的糖分及淀粉的耗資。Thenervoussystem.Thebrain,thespinalcordandthenerve-alsocontrolsbodyactivities.Thelowerpartsofthebraincontrolbasicfunctionssuchasbreathingandheartrateaswellasbodytemperature,hunger,andthirst.Abovetheseregionsarethecentersforsight,sound,touch,smell,andtaste,andtheregionsthatdirectvoluntarymuscularactivitiesofthearmsandlegs.Performedherearethehigherfunctionsofintegratingandprocessinginformation.神經系統——腦、脊髓及神經，也調控機體活動。腦的偏下部位控制著諸如呼吸、心跳、體溫、饑渴的基本活動。而腦的偏上部位則是視覺、聽覺、觸覺、嗅覺及味覺中心，也是指揮臂、腿隨意肌肉運動的地域。神經系統更高級的功能是整合、辦理信息。Thebrainreceivesandsendsinformationbymeansofnerves,manyofwhichliepartlyinthespinalcord.Thespinalcordisprotectedbythespinalcolumn.Nervesenterandleavethespinalcordateachlevelofthebody,travelingtoandfromthearms,legs,andtrunk.Thesenervesbringinformationfromthevarioussenseorgans.Theinformationisprocessedbythebrain,andthenmessagesarecarriedbacktomusclesandglandsthroughoutthebody.腦經過神經收集并傳達信息，很多神經部分地分布在脊髓里。脊髓由脊柱保護。在機體每一級，神經傳人、傳出脊髓，往返于臂、腿、軀體。這些神經輸送來自各種感覺器官的信息。信息經腦辦理后輸送回全身及腺體Thereproductivesystemisconstructeddifferentlyformalesandfemales.Themalereproductivesystemisresponsibleforproducing,transportingandmaintainingviablesperm(themalesexcell).Italsoproducesthemalesexhormone,testosterone,whichregulatesthedevelopmentofabeard,pubichair,adeepvoiceandotherbodilycharacteristicsoftheadultmale.男、女性的生殖系統不同樣樣。男性生殖系統產生、輸送、保持能存活的精子（男性性細胞）。它也分泌男性激素、睪酮，以此調理胡須、陰毛、深沉嗓音極其余成年男子身體發育的特色。Thefemaleproductivesystemisresponsibleforproducingandtransportingova(thefemale4sexcells),eliminatingovafromthebodywhentheyarenotfertilizedbysperm,nourishingandprovidingaplaceforgrowthofanembryowhenanovumisfertilizedbysperm,andnourishinganewbornchild.Thefemalereproductivesystemalsoproducesthefemalesexhormones,estrogenandprogesterone,whichregulatethedevelopmentofbreastsandotherbodilycharacteristicsofthematurefemale.女性生殖系統產生、輸送卵子（女性性細胞），將未受精的卵子排出體外，而當精、卵結合時，女性生殖系統培養、供應胚胎生長場所，并孕育再生兒。女性生殖系統也分泌女性性激素——雌激素和孕酮，以此調理乳房及其余成熟女性身體發育的特色。Theskinisacompletelayerthatprotectstheinnerstructuresofthebody,anditisthelargestofthebody'sorgans.Itkeepsoutforeignsubstancesandpreventsexcessivewaterevaporation.Thenervesintheskinprovidetactileinformation.Theskinalsohelpskeepthebody'stemperaturecloseto37°C,heatisconservedbyreducingbloodflowthroughtheskinorisexpendedbyincreasingbloodflowandbyevaporationofsweatfromtheskin.Hairandnailsareaccessorystructuresoftheskin.皮膚是保護肌體內層結構的圓滿層，也是機體的最大器官。皮膚防守外來侵襲，防范過多水分蒸發。皮膚上的神經供應觸覺信息。皮膚也能將體溫維持到98.6華氏度（約37攝氏度）。經過皮膚的血流量降低時，熱量就被存儲起來，經過皮膚的血流增加及汗液蒸發時，熱量就發散。頭發及指甲是皮膚的隸屬結構。CellsandTissues細胞與組織Inthispassage,youwilllearn:1.Humanbodysystemsasawhole2.Vitalpartsofacell3.FourkindsoftissuesCellsareorganizedintotissues,andtissuesarearrangedintoorgans,whichinturnaregroupedintosystems.Eachbodysystemservesitsspecificfunctions.Bearinmindhoweverthatthebodyfunctionsasawholenosystemisindependentoftheothers.Theyworktogethertomaintainthebody’sstateofinternalstability,dtermehomeostasis.Nowlet’sbeginourdiscussionwithcells,thesmallestunitoflivingmatterthatcanexistbyitself.細胞組成組織，組織組成器官，器官又進一步組成系統。人體的每個系統都有其特定功能，可是，請記住這里:機體是作為一個整體來發揮作用的，沒有哪個系統能夠獨立于其余系統而存在，是整系通通共同作用保持了機體內部的牢固狀態，即體內平衡。此刻，我們先議論細胞─能獨立存在活性物質的最小單位。Thebodycanbestudiedfromitssimplesttoitsmostcomplexlevel,beginningwiththecell.Allbodyfunctionsresultfromtheactivitiesofbillionsofthespecializedcells.Someplantsandanimalsconsistofonlyasinglecell.Othersarecomposedofmanybillionsofcells.從細胞開始，我們能夠從最簡單到最復雜的水平來研究機體。全部人體的功能都來自億萬個特定細胞活動，有的動植物僅由一個細胞組成，其余生物則由億萬個細胞組成。Cellsexistinavarietyofshapesandsizes.Theymay,forexample,becube-shapedorflat.Scientistswhostudycellshavedeterminedthatasinglecellmaybeaslargeasatennisballorsosmallthatthousandswouldfitonthepointofaneedle.Theyolkofahen’seggisactuallyavlargecell.Bycontrast,bacteriaeachoneofwhichisatinycellareamongthesmallestcells.Regardlessofitsshapeorsize,everycellcontainsthe“machineryneeded”tomaintainlife.Whilenormallycellsfunctionwithgreatefficiency,theyaresubjecttovariousdisordersthatresultindisease.細胞有很多種形狀和大小。列如：有可能是立方形或扁形的?？茖W家的研究發現單獨一個細胞能夠像網球同樣的大小，或小到幾千個細胞才能恰巧填滿針頭。雞的5蛋黃是一個特別大的單細胞。渺小的細菌呢算是最小的細胞。無論是細胞大小或形狀的不同，每個細胞都有“需要存活的系統”。對每個正常的細胞，有效力的細胞，都存在很多問題，能以致疾病。Thesizeofcellsisusuallymeasuredinmicrons.Amicronisamillionthofameter,andabout25,000micronsequaloneinch.Thesmallestbacteriaareabout0.2micronindiameter.Theaveragecellinthehumanbodyabouttenmicronsindiameterisaspeckbarelyvisiblewithouttheaidofamicroscope.細胞的大小是以“微米”為長度單位。微米是一米的一百萬分之一，25000微米等于一寸。最小的細菌的圓徑是0.2微米。人體正常細胞的議論圓徑約十微米，肉眼勉強能夠看獲得，不需要顯微鏡的幫助。Thestudyofcellsisthebranchofbiologycalledcytology.Thesciencethatdealswithcellsonthesmalleststructuralandfunctionalleveliscalledmolecularbiology.研究關于“細胞”是生物學的分支，成為細胞生物學。在最渺小水平針對細胞的結構及功能的研究成為分子生物學。Allcellsconsistofprotoplasm,the“livingjelly.The”protoplasmofatypicalcellformsthreevitalpartsthecellmembrane,thecytoplasm,andthenucleus.Themembraneenclosestheothercellstructures.Muchofthechemicalworkofthecellisdoneinthecytoplasm,whichsurroundsthenucleus.Thenucleus,enclosedbyitsownmembrane,isthecontrolcenterofthecell.(seeFigure1-1)全部細胞都是以“原生質”，又稱“生命膠質”所形成的。典型細胞的原生質形成了三個重要部分，細胞膜、細胞質和細胞核。細胞膜圈住了細胞的其余結構。大多數的化學反響都在細胞核周圍，細胞質完成的。被自己的膜包圍的細胞核是細胞的控制中心。thecellsMembrane細胞膜Cellscansurviveonlyinaliquidmediumthatbringsinfoodandcarriesawaywaste.Forone-celledorganismsthisfluidisanexternalbodyofwatertheocean,alake,orastream.Formany-celledplantsandanimals,however,themediumispartoftheorganisminplants,thesap;inanimals,theblood.細胞只能存活在能供養分又能除掉廢物的液體媒介中。對單細胞生物來說，這就是細胞外的液體，如：大海里、河里或水流中。在對多細胞生物而言，這類媒介就是生物體的一部分，植物以汁液的形式，動物以血液的形式。Thecellmembraneissemipermeable,ordifferentiallypermeablesomesubstancescanpassthroughit,butotherscannot.Thischaracteristicenablesthecelltoadmitusefulsubstancesandtorejectharmfulsubstancesfromthesurroundingfluidaswellastoforceout,orexcretewasteproductsintothefluid.細胞膜是半浸透性或差異性的浸透膜，即某些物質能浸透。這個特別性使細胞對細胞周圍只吸取了需要的物質而除掉去有害的物質，包括細胞內的廢物經過液體化后排出細胞外。Thecellmembraneisanextremelythinbuttoughbandofproteinandphospholipidmolecules.Phospholipidsarechemicalssimilartostoredfat.Ontheevidenceofelectronmicrographs,biologistsbelievethatithasporesthroughwhichcertainsmallmoleculespassintact.Substancesprobablypassthroughthecellmembraneinseveralways.Smallchamberslocatedonthecellmembranecalledcaveolaegatherchemicalsignalsandchannelthemintothecells.Thecaveolaemayalsohelpdistributeproteinsthroughoutthecell.Largemoleculesenterthecellbyaprocesscalleddiffusion,inwhichtheymaybedissolvedbysubstancesinthecellmembrane.Theycanthenthroughthemembranewithoutdifficulty.Somecellstakeinlarge6moleculesbymeansofpinocytosis.Inthisprocess,thecellmembraneformsapocketaroundlargemoleculesfloatingagainstit.Themolecule-and-fluid-filledpocketthenbreadsloosefromthemembranetobecomeabubblelikevacuole,andthevacuolethendriftsintothecytoplasm.Finally,thevacuolewallbreaksupandthemoleculesarereleasedintothecytoplasm.細胞膜是一種特別薄但確以很牢固的蛋白磷脂膜形成。磷脂是一種近似于存儲的脂肪的蛋白物質。經過電子顯微鏡，生物學家相信細胞膜有孔，使較小的物質圓滿能夠經過。物質可經過多種方式從細胞膜進入。細胞膜上的結構，稱“小穴”，可接受化學信號再傳到細胞內。小穴還可能參于細胞蛋白的分配。大的分子可經過“滲濾”進入細胞內，或被細胞膜內體分解，使它們更簡單的進入細胞內。有些細胞可經過“胞飲”方式吞飲較大的物質。這個過程是通過細胞膜在大物質形成了“帶”把它包圍著，將它以泡狀的“液泡”引入細胞質，最后包圍解散，大物質成功的進入細胞內。Thecytoplasm細胞質Thecytoplasmismainlywater.Itswatercontentvariesfromaminimumofabout65percenttoamaximumofabout95percent.Thesolidsinthecytoplasmincludegranularproteins,carbohydrates,dropletsoffat,andpigments.Thecytoplasmisthusacolloidalsystem.細胞質主要成分是“水”。水分含量有百分之65到最高，百分之95。細胞質內的固體包括蛋白顆粒、碳水化合物、脂肪小滴和色素。細胞質是膠體性的。Thecytoplasmmaybeeitherwateryorsyrupy,dependingontheconcentrationofsolidsdispersedinthefluid.Whenthesolidcontentdecreases,thesestructuresseemtovanish.Changesinconcentrationalsoproduceanapparentsteamingofthecytoplasmfromplacetoplacewithinthecell.Thisoccurs,forexample,whenfoodmoleculesenterthecell.細胞質可能是水性或糖漿性，依照散在細胞質內固體的濃度。當固體成分濃度增加，膜狀和纖維狀結果在細胞質顯出。而當固體成分濃度減少時，膜狀和纖維狀的結構就消失。濃度的變化還可以夠夠表現細胞質內局部流動的變化。食品分子進入時可見。Mostofthecell’sconstantworkofkeepingaliveisperformedinthecytoplasm.Herefoodmoleculesarechangedintothematerialneededforenergyandmaterialsforgrowthorstiffeningofthecellmembranearemanufacturesneededbytherestoftheorganism.Forexample,plantcellscontainingchlorophyllmanufactureglucoseaplantfoodfromcarbondioxideandwater.大多數為了細胞存活的工作都在此處（細胞質）完成的。在此處，食品物質將被轉化成供應細胞能量的資料和供應細胞生長的資料，或細胞膜的加強劑所生產。多細胞植物的細胞質還是生產了對其余生物供應食品的物質。列如：植物葉綠素所產生的葡萄糖，植物的食品，從水和二氧化碳合成。Oneofthecytoplasm’skeyenergytransactionsoccursinthesausage-shpdmitochondria.Eachmitochondrionhasaninnerandanoutermembrane.Likethecellmembrane,themembranesofthemitochondrionaresemipermeable.Foodmoleculesthatpassintothecytoplasmaretakenintothemitochondriaandoxidized,orburned,forenergy.細胞質能量變換的要點發生在錐狀形的線粒體。每個線粒體都有內膜和外膜。像細胞膜同樣，線粒體的膜也是半浸透性。進入線粒體的食品分子被氧化供應出能量。Theendoplasmicreticulum,anetworkofmembranoustubes,runsthroughthecytoplasm.Intheopinionofsomebiologists,thisnetworkisacontinuousstructurethatbeginsatthecellmembrane,twiststhroughthecytoplasm,andendsatthemembranesurroundingthenucleus.Locatedalongtheendoplasmicreticulumaswellaselsewhereinthecytoplasmarenumerous7ribosomes.Thesetinygranulesconsistinpartofribonucleicacid(RNA).Proteinsaremanufacturedattheribosomes.TheGolgicomplex,orGolgiapparatus,isamembranousstructurecomposedofstacksofthinsacs.NewlymadeproteinsmovefromtheendoplasmicreticulumtotheGolgicomplex,wheretheyarestoredforlatersecretion.胞漿網，在細胞質中由膜所形成管狀的網。有些生物學家認為這是一種連續性結構，始點為細胞膜，在細胞膜內扭絞，終點為細胞核的膜。分布于胞漿網包括細胞質中某處的是核糖體。這些小顆粒是核糖核酸所形成的。蛋白質是在核糖體合成的。高爾基體是膜狀囊包堆成層形成的。新合成的蛋白從胞漿網搬動到高爾基體存儲，為了今后分泌所用。Vacuolesdriftthroughthecytoplasmandusuallycarryfoodmoleculesinsolution.Lysosomesarestructuressomewhatsimilarinappearancetovacuolesbutdenser.Theyappeartohaveadigestivefunction.Eachlysosomeisfilledwithdigestiveenzymesandencasedinamembrane.Lysosomesarebelievedtobreakdownfoodsubstancesbroughtintothecellbypinocytosis.IthasbeensuggestedthattheGolgicomplexplaysapartintheformationoflysosomes.在細胞質內游動的液泡一般是帶著食品分子的溶液。溶酶體是一種有點像液泡的結構，但較稠。它是用來消化的。每個溶酶體的膜內都是添裝著消化酶。我們認為它是消化經過“胞飲”方式的大物質。也認為高爾基體對溶酶體的形成相關系。TheNucleus細胞核Nearthecenterofthecellisaroundishoroval-shapednucleus.Thenucleuscontrolsthegrowthanddivisionofthecell.Italsocontainsthestructuresthattransmithereditarytraits.細胞的中央，圓形或橢圓形的就是細胞核。細胞核控制細胞的生長和分化。也裝著遺傳信息。Enclosedbyatwo-layeredmembrane,thenucleuscontainsaliquidcallednucleoplasmaswellasstrandsofdeoxyribonucleicacid(DNA)coveredwithacoatingofprotein.AstrandofDNAconsistsofalongseriesofgenes,whicharetheunitsofheredityofplantsandanimals.Genesdeterminethecharacteristicsofacell.TheydothisbyregulatingtheproductionofRNA,whichinturncontrolsthemanufactureofspecificproteins.被兩層膜圈住著，細胞核內含有稱為“核質（漿）”的液體和脫氧核糖核酸的蛋白層。脫氧核糖核酸縷是很長的基因系列所組成的，它是植物和動物的遺傳信息?；驔Q定了細胞的特色。它是經過調理核糖核酸，使核糖核酸產出特異的蛋白。Humancells,forexample,makeonlyproteinsuniquetohumanbeingsDNAstrandsareusuallytoothinlystrungouttobeseenwithanopticalmicroscope.Becausethestrandsarereadilystainedwithdyes,theyarecalledchromatin.Whenacellbeginstodivide,however,thechromatinthickensintotheformofchromosomes.列如：人的細胞，只產出人獨到擁有的蛋白。脫氧核糖核酸縷一般都很渺小過光學顯微鏡能觀察到。由于脫氧核糖核酸縷能夠染色后部分被染，稱“染色質”。細胞分化過程中，染色體拾起變厚形成了“染色體”。Anucleusnotundergoingdivisionhasatleastonenucleolus.ThenucleoluscontainsaconcentrationofRNA.BiologiststhinkRNAismadeinitiallyinthenucleusaccordingtoaDNA“blueprint”andstoredthereuntilneededforproteinmanufacture細胞.核分化核仁不會減少，最少要有一個核仁。核仁含有豐富的核糖核酸。生物學家認為核糖核酸本來在核仁里，根據脫氧核糖核酸的宏圖造出而藏在此處直到有蛋白合成的需要。thenucleusofanimalcellsisasphericalstructurecalledthecentrosome,fromwhichastersradiate.Thecentrosomecontainsapairofroddedstructurecalledcentrioles,whichusuallylieatrightanglestoeachother.Althoughcentriolesandcentrosomeshavenotbeenseeninplantcells,8biologistsbelievethatplantcellscontainsimilarstructures.湊近動物的細胞核的圓形結構叫“中心體”，可見呈放射狀發散的星體。中心體內含有一對棍狀結構，稱為“中心?！?，一般都形成正確固定的角度。無法在植物細胞發現中心體和中心粒，但生物學家認為植物應該有存在近似功能的其余結構。Tissues組織Cellsareorganizedintotissuesthatperformspecificfunctions.Thefourbasictissuetypesareasfollows:多細胞組成了組織，為了特異的功能。四種基本的組織：Epithelialtissuescoversandprotectsbodystructuresandlinesorgans,vessels,andcavities.上皮組織:覆蓋及保護著身體結構和分清器官、導管和空腔。Connectivetissuessupportsandbindsbodystructures.Itcontainsfibersandothernonlivingmaterialbetweenthecells;includedarefattissues,cartilage,boneandblood.結締組:支柱和聯系著身體結構。包括細胞之間的纖維和其余無生物結構。包括脂肪組織、軟骨、骨頭和血液。Muscletissuescontractstoproducemovement.Thethreetypesare：skeletalorvoluntarymusclethatmovestheskeleton;thecardiacmuscleoftheheart;andthesmoothmusclethatformsthewallsoftheabdominalorgans.Cardiacandsmoothmusclecanfunctionwithoutconsciouscontrolandarethusdescribedasinvoluntarymuscle.肌肉組織:經過整理來產生動作。分為三種：骨骼肌，作用于一般骨骼搬動。心計，心臟的肌肉。圓滑肌，形成胃腸道壁的肌肉。心計和圓滑肌是非意識性，不隨意性肌肉。Nervoustissue——makesupthebrain,spinalcord,andnerves.Itcoordinatesandcontrolsbodyresponsesbytransmittingelectricalimpulses.神經組織:組成大腦、脊椎和神經。它是經過動作電位來超空身體。Thesimplesttissuesaremembranes.Mucousmembranessecretethickfluidcalledmucusthatprotectsunderlyingtissues.Serousmembranessecreteathin,wateryfluid.Theylinebodycavitiesandcoverorgans.最簡單的組織就是膜。粘液膜分泌出粘稠的膠液，起得組織保護作用。粘液組織分泌出較稀的粘液，起得身體導管的分界和覆蓋著各個器官。HumandiseasesInthispassageyouwilllearn:1.diseaseandpathology2.theclassificationofdiseases3.germs’invasionofthehumanbody4.thebody’defenseagainstinvasion5.thebody’simmunitytodiseasesThebriefsurveyofthehumanbodyinChapterOnehasgivenusaglimpseintotwodifferentstudiesthatareconsideredthefundamentalsofmedicalsciences,namelyanatomyandphysiology.However,thepictureisnotcompletewithoutconsideringpathology,thesciencethatdealswiththestructuralandfunctionalchangesproducedbythedisease.Infact,themodernapproachtothestudyofdisorderemphasizesthecloserelationshipofthepathologicalandphysiologicalaspectsandtheneedtounderstandthefundamentalsofeachintreatinganybodydiseases.第一章中，經過對人體的概論，即解剖學與生理學，我們對兩種被認為是醫學基礎的不同樣樣學科有了一個大概的印象?？墒侨羰俏覀儾豢紤]病理學，這門涉及由疾病帶來的結構和功能變化的學科，上述的人體概論就不是圓滿的。實質上，現代對疾病的研究方法重申了病理學與生理學方面的親近關系，重申了我們在治療任何人體疾病方面需要認識病9理學與生理學基礎的重要性。Thenwhatisadisease?Itmaybedefinedasaconditionthatimpairstheproperfunctionofthebodyorofoneofitsparts.Everylivingthing,bothplantsandanimals,cansuccumbtodisease.People,forexample,areofteninfectedbytinybacteria,butbacteria,inturn,canbeinfectedbyevenmoreminuteviruses.那么什么是疾病呢？它可能被定義為正常的功能或是部分功能碰到損害時的一種狀態。每一種生物、植物和動物，都會受制于疾病。比方，人類經常被渺小的細菌所感染，可是，反過來說，細菌又能夠被甚至更加渺小的病毒所感染。Hundredsofdifferentdiseasesexist.Eachhasitsownparticularsetofsymptomsandsigns,cluesthatenableaphysiciantodiagnosetheproblem.Asymptomissomethingapatientcandetect,suchasfever,bleeding,orpain.Asignissomethingadoctorcandetect,suchasaswollenbloodvesseloranenlargedinternalbodyorgan.很多種疾病存在于世。每一種都有其特定的癥狀、征兆和線索，醫生能以此診斷疾病之所在。癥狀是病人自己就能覺察到的，比方，高燒、流血，或是悲傷。而征兆則是醫生能夠觀察到的，比方，血管擴大或是體內器官腫大。Diseasescanbeclassifieddifferently.Forinstance,anepidemicdiseaseisonethatstrikesmanypersonsinacommunity.Whenitstrikesthesameregionyearafteryearitisanendemicdisease.Anacutediseasehasaquickonsetandrunsashortcourse.Anacuteheartattack,forexample,oftenhitswithoutwarningandcanbequicklyfatal.Achronicdiseasehasaslowonsetandrunsasometimesyears-longcourse.Thegradualonsetandlongcourseofrheumaticfevermakesitachronicailment.Betweentheacuteandchronic,anothertypeiscalledsubacute.疾病能夠劃分為不同樣樣的種類，比方，流行病是一種在某一社區內侵襲很多人的疾病。當它年復一年地侵襲同一社區，就成了一種地方病。急性病發生快，但病程短，舉個例子來說，急性心臟病發生經常沒有預兆，而且會很快致命。慢性病發生則慢，但病程有時會長達幾年之久。風濕熱正是由于發病慢、病程長而成為一種慢性失調病（慢性?。?。而介于急性與慢性之間的另一各種類，就被稱為亞急性。Diseasescanalsobeclassifiedbytheircausativeagents.Forinstance,aninfectious,orcommunicable,diseaseistheonethatcanbepassedbetweenpersonssuchasbymeansofairbornedropletsfromacoughorsneeze.Tinyorganismssuchasbacteriaandfungicanproduceinfectiousdiseases.Socanviruses.Socantinyworms.Whateverthecausativeagentmightbe,itsurvivesinthepersonitinfectsandispassedontoanother.Sometimes,adisease-producingorganismgetsintoapersonwhoshowsnosymptomsofthedisease.Theasymptomaticcarriercanthenpassthediseaseontosomeoneelsewithoutevenknowinghehasit.疾病也能夠依其病原體來劃分，比方，傳生病也叫作可流傳的疾病，就是一種經過咳嗽和打噴嚏造成的空氣小粒來流傳的疾病。極小的有機體，如，細菌和真菌能夠致傳生病。病毒和小蟲子也不例外。無論病原領悟是什么樣，只要它存活于人體內便能夠傳染給別人。有時，一個致病的有機體侵人人體后，該人卻沒有顯示帶病的癥狀。于是無癥狀的病原攜帶者甚至在自己也不知情的情況下就把疾病傳染給了別人。Noninfectiousdiseasesarecausedbymalfunctionsofthebody.Theseincludeorganortissuedegeneration,erraticcellgrowth,andfaultybloodformationandflow.Alsoincludedaredisturbancesofthestomachandintestine,theendocrinesystem,andtheurinaryandreproductivesystems.Somediseasescanbecausedbydietdeficiencies,lapsesinthebody'sdefensesystem,orapoorlyoperatingnervoussystem.非傳染性疾病是由身體功能失調惹起的。這包括血管或10組織退化、異常細胞生成，以及異常的血液生成和血液循環。自然其中也包括胃、腸、內分泌系統和泌尿生殖系統的紛雜。一些疾病也可能是由飲食不足、身體抵擋力下降、或是神經系統工作不造成的。Disabilityandillnessescanalsobeprovokedbypsychologicalandsocialfactors.Theseailmentsincludedrugaddiction,obesity,malnutrition,andpollution-causedhealthproblems.心理因素和社會因素也會惹起殘廢和疾病，這些病包括吸毒成性、肥胖、營養不良和由污染造成的健康問題。Furthermore,athousandormoreinheritablebirthdefectsresultfromalternationsingenepatterns.Sincetinygenesareresponsibleforproducingthemanychemicalsneededbythebody,missingorimproperlyoperatinggenescanseriouslyimpairhealth.Geneticdisordersthataffectbodychemistryarecalledinbornerrorsofmetabolism.Someformsofmentalretardationarehereditary.而且，有上千種以致為數更多的遺傳性出生弊端是由于基因變化而造成的。由于小小的基因負責著生產很多身體所需的化學物質，它的拋棄或是工作狀態不良都會嚴重損害健康。因基因失調而被影響了的身體化學反響被稱之為先天性代謝失調。一些眢力發育遲緩就是因遺傳而造成的。HowGermsInvadetheBody病菌是怎樣侵襲身體Humansliveinaworldwheremanyotherlivingthingscompeteforfoodandplacestobreed.Thepathogenicorganisms,orpathogens,oftenbroadlycalledgerms,thatcausemanydiseasesareabletoinvadethehumanbodyanduseitscellsandfluidsfortheirownneeds.Ordinarily,thebody'sdefensesystemcanwardofftheseinvaders.人類生活在有一個有很多其余生物競爭食品和求得繁衍的世界里。很多致病的有機體或病原體，平常被我們廣義地稱為病菌的東西能侵入人體并利用其細胞和組織液來供它們自己的需求。一般來講，身體防守系統能夠阻截這些入侵者。Pathogenicorganismscanenterthebodyinvariousways.Some-suchasthesethatcausethecommoncold,pneumonia,andtuberculosis-arebreathedin.Others-suchasthosethatcausevenerealdiseases-enterthroughsexualcontactofhumanbodies.Stillothers-suchasthosethatcausehepatitis,colitis,cholera,andtyphoidfever-getinthebodythroughcontaminatedfood,waterorutensils.病原有機體能經過多種方式進入身體。它們的一些是被呼吸進體內的，比方那些惹起一般感冒、肺炎和肺結核的病菌；其余的是經過人體性接觸進入的，比方那些惹起花柳病的病原體；還有其余的一些是經過污染了的食品、水或器皿進入體內的，比方那些惹起肝炎、霍亂和傷寒熱的病原體。Insectscanspreaddiseasebyactingasvectors,orcarriers.Fliescancarrygermsfromhumanwasteorothertaintedmaterialstofoodandbeverages.Germsmayalsoenterthebodythroughthebiteofamosquito,louse,orotherinsectvector.昆蟲作為媒介動物或是病原攜帶者會流傳疾病。蒼蠅能將病菌從人類的廢物或其余腐化的資料中帶到食品和飲料中去。經過蚊子、虱子或其余媒介動物的叮咬，病菌也可能進入體內。HowtheBodyFightsDisease身體是怎樣抵擋疾病的Asafirstlineofdefense,ahealthybodyhasanumberofphysicalbarriersagainstinfection.Theskinandmucousmembranescoveringthebodyorliningitsopeningsofferconsiderableresistancetoinvasionbybacteriaandotherinfectiousorganisms.Ifthesephysicalbarriersareinjuredorburned,infectionresistancedrops.Inminorcases,onlyboilsorpimplesmaydevelop.Inmajorcases,however,largeareasofthebodymightbecomeinfected.作為第一條防線，一個11健康的身體有很多屏障來抵擋感染的發生。覆蓋在體表也許器官張口處的皮膚和粘膜能在很大程度上抵擋細菌或其余感染體的入侵。若是這些屏障碰到了損壞或燒傷，身體對感染的抵擋力就會下降。在一些病情較輕的病例中，疥子和小膿胞可能會發生。在病情較重的病例中，身體的大面積地域則可能會被感染。Breathingpassagesareespeciallyvulnerabletoinfection.Fortunately,theyarelinedwithmucus-secretingcellsthattraptinyorganismsanddustparticles.Also,minutehairscalledcilialinethebreathingpassages,wavelikeafieldofwheat,andgentlysweepmatteroutoftherespiratoryt