醫(yī)學(xué)英語(閱讀一分冊)翻譯及其規(guī)范標(biāo)準(zhǔn)答案

1、Chapter1Passage1HumanBodyInthispassageyouwilllearn:1.Classificationoforgansystems2.Structureandfunctionofeachorgansystem3.AssociatedmedicaltermsTounderstandthehumanbodyitisnecessarytounderstandhowitspartsareputtogetherandhowtheyfunction.Thestudyofthebodysstructureiscalledanatomy;thestudyofthebodysfu

2、nctionisknownasphysiology.Otherstudiesofhumanbodyincludebiology,cytology,embryology,histology,endocrinology,hematology,immunology,psychologyetc.了解人體各部分的組成及其功能，對于認(rèn)識人體是必需的。研究人體結(jié)構(gòu)的科學(xué)叫解剖學(xué)；研究人體功能的科學(xué)叫生理學(xué)。其他研究人體的科學(xué)包括生物學(xué)、細(xì)胞學(xué)、胚胎學(xué)、組織學(xué)、內(nèi)分泌學(xué)、血液學(xué)、遺傳學(xué)、免疫學(xué)、心理學(xué)等等。Anatomistsfinditusefultodividethehumanbodyintotensys

3、tems,thatis,theskeletalsystem,themuscularsystem,thecirculatorysystem,therespiratorysystem,thedigestivesystem,theurinarysystem,theendocrinesystem,thenervoussystem,thereproductivesystemandtheskin.Theprincipalpartsofeachofthesesystemsaredescribedinthisarticle.解剖學(xué)家發(fā)現(xiàn)把整個人體分成骨骼、肌肉、循環(huán)、呼吸、消化、泌尿、內(nèi)分泌、神經(jīng)、生殖系統(tǒng)以

4、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(tǒng)的主要部分。Theskeletalsystemismadeofbones,jointsbetweenbones,andcartilage.Itsfunctionistoprovidesupportandprotectionforthesofttissuesandtheorgansofthebodyandtoprovidepointsofattachmentforthemusclesthatmovethebody.Thereare206bonesinthehumanskeleton.Theyhavevariousshapes-long,shor

5、t,cube-shaped,flat,andirregular.Manyofthelongboneshaveaninteriorspacethatisfilledwithbonemarrow,wherebloodcellsaremade.骨骼系統(tǒng)由骨、關(guān)節(jié)以及軟骨組成。它對軟組織及人體器官起到支持和保護(hù)作用，并牽動骨胳肌，引起各種運(yùn)動。人體有206根骨頭。骨形態(tài)不一，有長的、短、立方的、扁的及不規(guī)則的。許多長骨里有一個內(nèi)層間隙，里面充填著骨髓，這即是血細(xì)胞的制造場所。Ajointiswherebonesarejoinedtogether.Theconnectioncanbesoclosetha

6、tnomovementispossible,asisthecaseintheskull.Otherkindsofjointspermitmovement:eitherbackandforthinoneplane-aswiththehingejointoftheelbow-ormovementaroundasingleaxis-aswiththepivotjointthatpermitstheheadtorotate.Awiderangeofmovementispossiblewhentheball-shapedendofonebonefitsintoasocketattheendofanoth

7、erbone,astheydointheshoulderandhipjoints.關(guān)節(jié)把骨與骨連接起來。顱骨不能運(yùn)動，是由于骨與骨之間的連接太緊密。但其它的關(guān)節(jié)可允許活動，如一個平面上的前后屈伸運(yùn)動，如肘關(guān)節(jié)；或是繞軸心旋轉(zhuǎn)運(yùn)動，如樞軸點(diǎn)允許頭部轉(zhuǎn)動。如果一根骨的球形末端插入另一根骨的臼槽里，大輻度的運(yùn)動（如肩關(guān)節(jié)、髖關(guān)節(jié)）即成為可能。Cartilageisamoreflexiblematerialthanbone.Itservesasaprotective,cushioninglayerwherebonescometogether.Italsoconnectstheribstothebrea

8、stboneandprovidesastructuralbaseforthenoseandtheexternalear.Aninfantsskeletonismadeofcartilagethatisgraduallyreplacedbyboneastheinfantgrowsintoanadult.軟骨是一種比一般骨更具韌性的物質(zhì)。它是骨連結(jié)的保護(hù)、緩沖層。它把肋骨與胸骨連結(jié)起來，也是鼻腔與內(nèi)耳的結(jié)構(gòu)基礎(chǔ)。一個嬰兒的骨骼就是由軟骨組成，然后不斷生長、骨化，使嬰兒長大成人。Themuscularsystemallowsthebodytomove,anditscontractionsproduc

9、eheat,whichhelpsmaintainaconstantbodytemperature.Striatedmusclescanbeconsciouslycontrolled.Theendsofthesemusclesareattachedtodifferentbonesbyconnectivetissuebandssothatwhenthemusclecontracts,onebonemovesinrelationtotheother.Thismakesitpossibletomovethewholebody,aswhenwalking,ortomovejustonepartofthe

10、body,aswhenbendingafinger.Contractionsoftheheartandsmoothmusclesarenotunderconsciouscontrol.Smoothmusclesarefoundinthewallsoforganssuchasthestomachandtheintestinesandservetomovethecontentsoftheseorgansthroughthebody肌肉系統(tǒng)使軀體運(yùn)動，肌肉收縮產(chǎn)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(jié)締組織使肌肉末端附著于不同的骨面上，所以當(dāng)肌肉收縮時，兩骨彼此靠近而產(chǎn)生運(yùn)動。

11、這也就使整個人體可以運(yùn)動起來，如走路，運(yùn)動軀體某個部位，如彎曲手指。心臟收縮和平滑肌收縮就不是被意識所控制的。器官壁內(nèi)層的平滑肌，如胃腸壁的平滑肌把胃腸中的物質(zhì)運(yùn)送到全身。Thecirculatorysystem.Allpartsofthebodymusthavenourishmentandoxygeninordertofunctionandgrow,andtheirwasteproductsmustberemovedbeforetheyaccumulateandpoisonthebody.Thecirculatorysystemdistributesneededmaterialsandrem

12、ovesunneededones.Itismadeupoftheheart,bloodvessels,andblood,whichtogethermakeupthecardiovascularsystem.Thebloodisalsopartofthebodysdefensesystem.Ithasantibodiesandwhitebloodcellsthatprotectthebodyagainstforeigninvaders.循環(huán)系統(tǒng)：機(jī)體的所有部分需要營養(yǎng)物質(zhì)和氧氣來使之發(fā)揮功能和生長，也需要在這些器官所產(chǎn)生的廢物積聚而危害生命之前將其排除。循環(huán)系統(tǒng)運(yùn)送有用物質(zhì)，排泄廢物。心血管系統(tǒng)

13、是循環(huán)系統(tǒng)的組成之一；心血管系統(tǒng)包括心臟、血管及血液。血液也是機(jī)體防御系統(tǒng)的一個部分，血液中有抗體及白細(xì)胞來防止機(jī)體受到外來的侵襲。Theheartisamusclethatisdividedintotwonearlyidenticalhalves:onehalfreceivesbloodfromthelungsandsendsittotherestofthebody,theotherhalfsendsbloodthathastraveledthroughthebodybacktothelungs.Whentheheartmusclecontracts,thebloodisforcedouti

14、ntoarteriesandenterssmallcapillaries.Bloodreturnstotheheartthroughveins.心臟是一塊被分為幾乎對等兩半的肌肉。一半吸收來自肺部的血液，并將血液運(yùn)送到機(jī)體的其余部位，另一半使流經(jīng)全身的血液回流人肺。心臟收縮時，動脈把全身血液輸送到毛細(xì)血管。靜脈輸送血液返回心臟。Alsofunctioningincirculationisthelymphaticsystem.Someofthefluidthatsurroundscellsdoesnotreenterthebloodvesselsdirectly.Thisfluid,called

15、lymph,returnstotheheartbywayofanothersystemofchannels-thelymphvessels.Lymphnodesalongthesevesselsfilterthefluidbeforeitreenterstheblood.Thespleenisalargelymphaticorganthatfilterstheblood.淋巴系統(tǒng)也是循環(huán)系統(tǒng)的一個組成部分。一些細(xì)胞周圍的體液不是直接回流入血管通道，這種體液叫淋巴液，它是流經(jīng)另一個管道系統(tǒng)淋巴管而回流人心臟。沿淋巴管的淋巴結(jié)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。Ther

16、espiratorysystemtakesinoxygenfromtheairandexpelscarbondioxideandwatervapor.Airentersthenoseandmouthandtravelsthroughthelarynx,andtrachea.Thetracheadividestoentereachofthetwolungsandthendividesmorethan20timestoformaverylargenumberofsmallairspaces.Oxygenfromtheairentersthebloodthroughcapillariesinthew

17、allsoftheseairspaces,andthebloodreleasecarbondioxideintotheairspacestobeexhaled.呼吸系統(tǒng)從空氣中攝取氧氣，并將二氧化碳、水蒸氣排出體外?？諝饨?jīng)鼻腔、口腔人喉管、氣管。氣管分成左右支氣管，各連結(jié)左右肺，左右支氣管再分枝20多次，在終端形成大量微小的肺泡。從空氣攝取的氧氣流經(jīng)這些肺泡壁內(nèi)的毛細(xì)血管流入血液，血液再經(jīng)肺泡把釋放出的二氧化碳排出體外。Thedigestivesystemconsistsofatubeextendingfromthemouthtotheanus.Init,foodandfluidsaretak

18、enin,movedthroughthebody,andbrokendownintosmallmoleculesthatareabsorbedintothecirculatorysystem.Thisbreakdown,knownasdigestion,isbothamechanicalandachemicalprocess.消化系統(tǒng)是一個從口腔直到肛門的管道。食物和液體在消化道里被吸收，在腸道里移動時，被分解成小分子物質(zhì)后再進(jìn)入循環(huán)系統(tǒng)。這種分解，即消化，是一個機(jī)械過程，也是一個化學(xué)過程。Foodentersthroughthemouth,wherechewingandsalivastart

19、tobreakitupandmakeiteasiertoswallow.Next,thefoodtravelsdownthroughtheesophagustothestomach.Contractionsofthestomachsmuscularwallcontinuetobreakdownthefoodmechanically,andchemicaldigestioncontinueswhenacidandenzymesaresecretedintothestomachcavity.食物進(jìn)入口腔里，咀嚼和唾液開始將食物粉碎，使之便于吞咽。接著，食物經(jīng)食管人胃。胃肌壁的收縮繼續(xù)機(jī)械化地分解食

20、物，而當(dāng)酸和酶分泌入胃腔時，化學(xué)性消化開始。Theliquifiedfoodgraduallypassesintothesmallintestine.Inthefirstpartofthesmallintestine,calledtheduodenum,enzymesfromthepancreasareadded.Theseenzymescompletethechemicalbreakdownofthefood.Thedigestionoffatisaidedbybile,whichismadeintheliverandstoredinthegallbladder.Thesmallintest

21、ineofanadultisabout21feet(6.4meters)long.Mostofitslengthisdevotedtoabsorbingthenutrientsreleasedduringthesedigestiveactivities.液體化食物逐漸進(jìn)入小腸。小腸的起始部分叫十二指腸，胰腺分泌的酶輔助食物消化。這些酶完成食物的化學(xué)分解。肝臟分泌的膽汁貯存在膽囊內(nèi)，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。小腸的大部分腸段用來吸收消化過程中釋放的營養(yǎng)物質(zhì)。Theliquidremainderofthefoodentersthelargeintestine,o

22、rcolon,whichisabout12feet(3.7meters)long.Itismorethantwiceaswideasthesmallintestine.Inthelargeintestinemostofthefluidisabsorbed,andtherelativelydryresiduesareexpelled.液狀的剩余食物進(jìn)入大腸，或結(jié)腸，它大約有12英尺(3.7米)長。大腸是小腸的兩倍多寬。大部分液體在大腸內(nèi)被吸收，相對干化的殘余物被排出體外。Theurinarysystemmaintainsnormallevelsofwaterandofcertainsmallmo

23、leculessuchassodiumandpotassiuminthebody.Itdoesthisbypassingbloodthroughthekidneys,twoefficientfilteringorgansthatgetridofanyexcessofvariousmoleculesandconservethosemoleculesthatareinshortsupply.泌尿系統(tǒng)維持水分及體內(nèi)某些小分子物質(zhì)，如鈉、鉀的正常水平。身體是通過讓腎過濾血液來做到這一點(diǎn)的。腎是兩個有效的過濾器官，它濾出各種多余的小分子物質(zhì)，保留那些供應(yīng)不足的小分子物質(zhì)。Thefluidthatleav

24、esthekidneys,knownasurine,travelsthroughatubecalledtheuretertothebladder.Thebladderholdstheurineuntilitisvoidedfromthebodythroughanothertube,theurethra.從腎流出的液體，即尿，通過輸尿管人膀胱。膀胱起貯存尿液的作用，直到尿經(jīng)膀胱另一端的管道排出。Theendocrinesystem.Thetwosystemsthatcontrolbodyactivitiesaretheendocrinesystemandthenervoussystem.Thef

25、ormerexertsitscontrolbymeansofchemicalmessengerscalledhormones.Hormonesareproducedbyavarietyofendocrineglands,whichreleasethehormonesdirectlyintothebloodstream.內(nèi)分泌系統(tǒng)。內(nèi)分泌和神經(jīng)是調(diào)控機(jī)體活動的兩個系統(tǒng)，前者依靠其化學(xué)信使激素發(fā)揮作用。激素是由各種內(nèi)分泌腺體制造，并直接被釋放入血流Amajorglandisthepituitary,whichislocatedunderthebraininthemiddleofthehead.It

26、producesatleasteighthormones,whichaffectgrowth,kidneyfunction,anddevelopmentofthesexorgans.Becausesomeofthepituitaryshormonesstimulateotherglandstoproducetheirownhormones,thepituitarycalledthemastergland.腦垂體是一個主要腺體，它位于頭中部腦下方。它至少分泌八種激素，這些激素對人體生長、肝功能及性器官發(fā)育有影響。因?yàn)槟X垂體分泌的一些激素促進(jìn)其他腺體分泌激素，所以腦垂體是主要腺體。Anotherg

27、land,thethyroid,islocatedbetweenthecollarbones.Itshormonecontrolstherateofthebodysmetabolism.Thesexorgans(ovariesendtestes)makethesexcellsandalsomakehormonesthatcontrolcertaincharacteristicsofmalesandfemales.Locatedontopofeachkidneyistheadrenalgland,whichproducescortisoneandadrenaline.Thepancreaspro

28、ducesnotonlydigestiveenzymesbutalso3insulinandglucagon,whichcontrolthebodysuseofsugarandstarches.另一個腺體，甲狀腺，位于鎖骨之間。甲狀腺激素調(diào)控著機(jī)體新陳代謝的速度。性器官(卵巢、睪丸)分泌性細(xì)胞和性激素，這些激素控制著男性和女性的某些特征。每邊腎上方是腎上腺，它分泌可的松和腎上腺激素。胰腺不僅分泌消化酶，而且分泌胰島素和高血糖素，這兩種激素控制機(jī)體的糖分及淀粉的消耗。Thenervoussystem.Thebrain,thespinalcordandthenerve-alsocontrolsbo

29、dyactivities.Thelowerpartsofthebraincontrolbasicfunctionssuchasbreathingandheartrateaswellasbodytemperature,hunger,andthirst.Abovetheseregionsarethecentersforsight,sound,touch,smell,andtaste,andtheregionsthatdirectvoluntarymuscularactivitiesofthearmsandlegs.Performedherearethehigherfunctionsofintegr

30、atingandprocessinginformation.神經(jīng)系統(tǒng)腦、脊髓及神經(jīng)，也調(diào)控機(jī)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(yùn)動的區(qū)域。神經(jīng)系統(tǒng)更高級的功能是整合、處理信息。Thebrainreceivesandsendsinformationbymeansofnerves,manyofwhichliepartlyinthespinalcord.Thespinalcordisprotectedbythespinalcolumn.Nervesenterandleavethespinalcor

31、dateachlevelofthebody,travelingtoandfromthearms,legs,andtrunk.Thesenervesbringinformationfromthevarioussenseorgans.Theinformationisprocessedbythebrain,andthenmessagesarecarriedbacktomusclesandglandsthroughoutthebody.腦通過神經(jīng)收集并傳送信息，許多神經(jīng)部分地分布在脊髓里。脊髓由脊柱保護(hù)。在機(jī)體每一級，神經(jīng)傳人、傳出脊髓，往返于臂、腿、軀體。這些神經(jīng)輸送來自各種感覺器官的信息。信息經(jīng)腦

32、處理后輸送回全身及腺體Thereproductivesystemisconstructeddifferentlyformalesandfemales.Themalereproductivesystemisresponsibleforproducing,transportingandmaintainingviablesperm(themalesexcell).Italsoproducesthemalesexhormone,testosterone,whichregulatesthedevelopmentofabeard,pubichair,adeepvoiceandotherbodilychar

33、acteristicsoftheadultmale.男、女性的生殖系統(tǒng)不同。男性生殖系統(tǒng)產(chǎn)生、輸送、維持能存活的精子(男性性細(xì)胞)。它也分泌男性激素、睪酮，以此調(diào)節(jié)胡須、陰毛、深沉嗓音極其他成年男子身體發(fā)育的特征。Thefemaleproductivesystemisresponsibleforproducingandtransportingova(thefemalesexcells),eliminatingovafromthebodywhentheyarenotfertilizedbysperm,nourishingandprovidingaplaceforgrowthofanembryow

34、henanovumisfertilizedbysperm,andnourishinganewbornchild.Thefemalereproductivesystemalsoproducesthefemalesexhormones,estrogenandprogesterone,whichregulatethedevelopmentofbreastsandotherbodilycharacteristicsofthematurefemale.女性生殖系統(tǒng)產(chǎn)生、輸送卵子(女性性細(xì)胞)，將未受精的卵子排出體外，而當(dāng)精、卵結(jié)合時，女性生殖系統(tǒng)培養(yǎng)、提供胚胎生長場所，并孕育新生兒。女性生殖系統(tǒng)也分泌女

35、性性激素雌激素和孕酮，以此調(diào)節(jié)乳房及其他成熟女性身體發(fā)育的特征。Theskinisacompletelayerthatprotectstheinnerstructuresofthebody,anditisthelargestofthebodysorgans.Itkeepsoutforeignsubstancesandpreventsexcessivewaterevaporation.Thenervesintheskinprovidetactileinformation.Theskinalsohelpskeepthebodystemperaturecloseto37C,heatisconserv

36、edbyreducingbloodflowthroughtheskinorisexpendedbyincreasingbloodflowandbyevaporationofsweatfromtheskin.Hairandnailsareaccessorystructuresoftheskin.皮膚是保護(hù)肌體內(nèi)層結(jié)構(gòu)的完整層，也是機(jī)體的最大器官皮膚防御外來侵襲，防止過多水分蒸發(fā)。皮膚上的神經(jīng)提供觸覺信息。皮膚也能將體溫維持到98.6華氏度（約37攝氏度）。通過皮膚的血流量降低時，熱量就被儲存起來，通過皮膚的血流增加及汗液蒸發(fā)時，熱量就散發(fā)。頭發(fā)及指甲是皮膚的附屬結(jié)構(gòu)。CellsandTissue

37、s細(xì)胞與組織Inthispassage,youwilllearn:1.Humanbodysystemsasawhole2.Vitalpartsofacell3.FourkindsoftissuesCellsareorganizedintotissues,andtissuesarearrangedintoorgans,whichinturnaregroupedintosystems.Eachbodysystemservesitsspecificfunctions.Bearinmindhoweverthatthebodyfunctionsasawholenosystemisindependento

38、ftheothers.Theyworktogethertomaintainthebodysstateofinternalstability,termedhomeostasis.Nowletsbeginourdiscussionwithcells,thesmallestunitoflivingmatterthatcanexistbyitself.細(xì)胞構(gòu)成組織，組織構(gòu)成器官，器官又進(jìn)一步構(gòu)成系統(tǒng)。人體的每個系統(tǒng)都有其特定功能，但是，請記住這里:機(jī)體是作為一個整體來發(fā)揮作用的，沒有哪個系統(tǒng)能夠獨(dú)立于其他系統(tǒng)而存在，是整體系統(tǒng)共同作用保持了機(jī)體內(nèi)部的穩(wěn)定狀態(tài)，即體內(nèi)平衡。現(xiàn)在，我們先討論細(xì)胞-能獨(dú)立存

39、在活性物質(zhì)的最小單位。Thebodycanbestudiedfromitssimplesttoitsmostcomplexlevel,beginningwiththecell.Allbodyfunctionsresultfromtheactivitiesofbillionsofthespecializedcells.Someplantsandanimalsconsistofonlyasinglecell.Othersarecomposedofmanybillionsofcells.從細(xì)胞開始，我們能夠從最簡單到最復(fù)雜的水平來研究機(jī)體。所有人體的功能都來自億萬個特定細(xì)胞活動有的動植物僅由一個細(xì)胞

40、構(gòu)成，其他生物則由億萬個細(xì)胞構(gòu)成。Cellsexistinavarietyofshapesandsizes.Theymay,forexample,becube-shapedorflat.Scientistswhostudycellshavedeterminedthatasinglecellmaybeaslargeasatennisballorsosmallthatthousandswouldfitonthepointofaneedle.Theyolkofahenseggisactuallyaverylargecell.Bycontrast,bacteriaeachoneofwhichisati

41、nycellareamongthesmallestcells.Regardlessofitsshapeorsize,everycellcontainsthe“machinery”neededtomaintainlife.Whilenormallycellsfunctionwithgreatefficiency,theyaresubjecttovariousdisordersthatresultindisease.細(xì)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(xué)家的研究發(fā)現(xiàn)單獨(dú)一個細(xì)胞可以像網(wǎng)球一樣的大小，或小到幾千個細(xì)胞才能剛好填滿針頭。雞的蛋黃是一個非常大的單細(xì)胞。微小的細(xì)菌呢算是

42、最小的細(xì)胞。不管是細(xì)胞大小或形狀的不同，每個細(xì)胞都有“需要存活的機(jī)制”。對每個正常的細(xì)胞，有效力的細(xì)胞，都存在許多問題，能導(dǎo)致疾病。Thesizeofcellsisusuallymeasuredinmicrons.Amicronisamillionthofameter,andabout25,000micronsequaloneinch.Thesmallestbacteriaareabout0.2micronindiameter.Theaveragecellinthehumanbodyabouttenmicronsindiameterisaspeckbarelyvisiblewithoutthe

43、aidofamicroscope.細(xì)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(xì)菌的圓徑是0.2微米。人體正常細(xì)胞的評價圓徑約十微米，肉眼勉強(qiáng)可以看得到，不需要顯微鏡的幫助。Thestudyofcellsisthebranchofbiologycalledcytology.Thesciencethatdealswithcellsonthesmalleststructuralandfunctionalleveliscalledmolecularbiology.研究關(guān)于“細(xì)胞”是生物學(xué)的分支，成為細(xì)胞生物學(xué)。在最微小水平針對細(xì)胞的結(jié)構(gòu)及功能的研究成為分

44、子生物學(xué)。Allcellsconsistofprotoplasm,the“l(fā)ivingjelly.”Theprotoplasmofatypicalcellformsthreevitalpartsthecellmembrane,thecytoplasm,andthenucleus.Themembraneenclosestheothercellstructures.Muchofthechemicalworkofthecellisdoneinthecytoplasm,whichsurroundsthenucleus.Thenucleus,enclosedbyitsownmembrane,isthec

45、ontrolcenterofthecell.(seeFigure1-1)所有細(xì)胞都是以“原生質(zhì)”，又稱“生命膠質(zhì)”所形成的。典型細(xì)胞的原生質(zhì)形成了三個重要部分，細(xì)胞膜、細(xì)胞質(zhì)和細(xì)胞核。細(xì)胞膜圈住了細(xì)胞的其他結(jié)構(gòu)。大部分的化學(xué)反應(yīng)都在細(xì)胞核周圍，細(xì)胞質(zhì)完成的。被自己的膜包圍的細(xì)胞核是細(xì)胞的控制中心。thecellsMembrane細(xì)胞膜Cellscansurviveonlyinaliquidmediumthatbringsinfoodandcarriesawaywaste.Forone-celledorganismsthisfluidisanexternalbodyofwatertheocean

46、,alake,orastream.Formany-celledplantsandanimals,however,themediumispartoftheorganisminplants,thesap;inanimals,theblood.細(xì)胞只能存活在能供養(yǎng)分又能排除廢物的液體媒介中。對單細(xì)胞生物來說，這就是細(xì)胞外的液體，如：大海里、河里或水流中。在對多細(xì)胞生物而言，這種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,ordifferentiallypermeablesomesubstancescanpassthroug

47、hit,butotherscannot.Thischaracteristicenablesthecelltoadmitusefulsubstancesandtorejectharmfulsubstancesfromthesurroundingfluidaswellastoforceout,orexcretewasteproductsintothefluid.細(xì)胞膜是半滲透性或區(qū)別性的滲透膜，即某些物質(zhì)能滲透。這個特殊性使細(xì)胞對細(xì)胞周圍只吸收了需要的物質(zhì)而排除掉有害的物質(zhì)，包括細(xì)胞內(nèi)的廢物通過液體化后排出細(xì)胞外。Thecellmembraneisanextremelythinbuttoughba

48、ndofproteinandphospholipidmolecules.Phospholipidsarechemicalssimilartostoredfat.Ontheevidenceofelectronmicrographs,biologistsbelievethatithasporesthroughwhichcertainsmallmoleculespassintact.Substancesprobablypassthroughthecellmembraneinseveralways.Smallchamberslocatedonthecellmembranecalledcaveolaeg

49、atherchemicalsignalsandchannelthemintothecells.Thecaveolaemayalsohelpdistributeproteinsthroughoutthecell.Largemoleculesenterthecellbyaprocesscalleddiffusion,inwhichtheymaybedissolvedbysubstancesinthecellmembrane.Theycanthenthroughthemembranewithoutdifficulty.Somecellstakeinlargemoleculesbymeansofpin

50、ocytosis.Inthisprocess,thecellmembraneformsapocketaroundlargemoleculesfloatingagainstit.Themolecule-and-fluid-filledpocketthenbreadsloosefromthemembranetobecomeabubblelikevacuole,andthevacuolethendriftsintothecytoplasm.Finally,thevacuolewallbreaksupandthemoleculesarereleasedintothecytoplasm.細(xì)胞膜是一種非常

51、薄但確以很堅(jiān)固的蛋白磷脂膜形成。磷脂是一種類似于儲存的脂肪的蛋白物質(zhì)。通過電子顯微鏡，生物學(xué)家相信細(xì)胞膜有孔，使較小的物質(zhì)完全可以通過。物質(zhì)可通過多種方式從細(xì)胞膜進(jìn)入。細(xì)胞膜上的結(jié)構(gòu)，稱“小穴”，可接受化學(xué)信號再傳到細(xì)胞內(nèi)。小穴還可能參于細(xì)胞蛋白的分配。大的分子可通過“滲濾”進(jìn)入細(xì)胞內(nèi)，或被細(xì)胞膜內(nèi)體分解，使它們更容易的進(jìn)入細(xì)胞內(nèi)。有些細(xì)胞可通過“胞飲”方式吞飲較大的物質(zhì)。這個過程是通過細(xì)胞膜在大物質(zhì)形成了“帶”把它包圍著，將它以泡狀的“液泡”引入細(xì)胞質(zhì)，最后包圍解散，大物質(zhì)成功的進(jìn)入細(xì)胞內(nèi)。Thecytoplasm細(xì)胞質(zhì)Thecytoplasmismainlywater.Itswaterco

52、ntentvariesfromaminimumofabout65percenttoamaximumofabout95percent.Thesolidsinthecytoplasmincludegranularproteins,carbohydrates,dropletsoffat,andpigments.Thecytoplasmisthusacolloidalsystem.細(xì)胞質(zhì)主要成分是“水”。水分含量有百分之65到最高，百分之95。細(xì)胞質(zhì)內(nèi)的固體包括蛋白顆粒、碳水化合物、脂肪小滴和色素。細(xì)胞質(zhì)是膠體性的。Thecytoplasmmaybeeitherwateryorsyrupy,depen

53、dingontheconcentrationofsolidsdispersedinthefluid.Whenthesolidcontentdecreases,thesestructuresseemtovanish.Changesinconcentrationalsoproduceanapparentsteamingofthecytoplasmfromplacetoplacewithinthecell.Thisoccurs,forexample,whenfoodmoleculesenterthecell.細(xì)胞質(zhì)可能是水性或糖漿性，根據(jù)散在細(xì)胞質(zhì)內(nèi)固體的濃度。當(dāng)固體成分濃度增多，膜狀和纖維狀結(jié)果在

54、細(xì)胞質(zhì)顯出。而當(dāng)固體成分濃度減少時，膜狀和纖維狀的結(jié)構(gòu)就消失。濃度的變化還可以表現(xiàn)細(xì)胞質(zhì)內(nèi)局部流動的變化。食物分子進(jìn)入時可見。Mostofthecellsconstantworkofkeepingaliveisperformedinthecytoplasm.Herefoodmoleculesarechangedintothematerialneededforenergyandmaterialsforgrowthorstiffeningofthecellmembranearemanufacturesneededbytherestoftheorganism.Forexample,plantcell

55、scontainingchlorophyllmanufactureglucoseaplantfoodfromcarbondioxideandwater.大部分為了細(xì)胞存活的工作都在此處(細(xì)胞質(zhì))完成的。在此處，食物物質(zhì)將被轉(zhuǎn)化成提供細(xì)胞能量的材料和提供細(xì)胞生長的材料，或細(xì)胞膜的增強(qiáng)劑所生產(chǎn)。多細(xì)胞植物的細(xì)胞質(zhì)還是生產(chǎn)了對其他生物提供食物的物質(zhì)。列如：植物葉綠素所產(chǎn)生的葡萄糖，植物的食物，從水和二氧化碳合成。Oneofthecytoplasmskeyenergytransactionsoccursinthesausage-shapedmitochondria.Eachmitochondrionh

56、asaninnerandanoutermembrane.Likethecellmembrane,themembranesofthemitochondrionaresemipermeable.Foodmoleculesthatpassintothecytoplasmaretakenintothemitochondriaandoxidized,orburned,forenergy.細(xì)胞質(zhì)能量轉(zhuǎn)換的要點(diǎn)發(fā)生在錐狀形的線粒體。每個線粒體都有內(nèi)膜和外膜。像細(xì)胞膜一樣，線粒體的膜也是半滲透性。進(jìn)入線粒體的食物分子被氧化提供出能量。Theendoplasmicreticulum,anetworkofmemb

57、ranoustubes,runsthroughthecytoplasm.Intheopinionofsomebiologists,thisnetworkisacontinuousstructurethatbeginsatthecellmembrane,twiststhroughthecytoplasm,andendsatthemembranesurroundingthenucleus.Locatedalongtheendoplasmicreticulumaswellaselsewhereinthecytoplasmarenumerousribosomes.Thesetinygranulesco

58、nsistinpartofribonucleicacid(RNA).Proteinsaremanufacturedattheribosomes.TheGolgicomplex,orGolgiapparatus,isamembranousstructurecomposedofstacksofthinsacs.NewlymadeproteinsmovefromtheendoplasmicreticulumtotheGolgicomplex,wheretheyarestoredforlatersecretion.胞漿網(wǎng)，在細(xì)胞質(zhì)中由膜所形成管狀的網(wǎng)。有些生物學(xué)家認(rèn)為這是一種連續(xù)性結(jié)構(gòu)，始點(diǎn)為細(xì)胞膜，

59、在細(xì)胞膜內(nèi)扭絞，終點(diǎn)為細(xì)胞核的膜。分布于胞漿網(wǎng)包括細(xì)胞質(zhì)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(zhì)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(wǎng)移動到高爾基體儲存，為了后來分泌所用。Vacuolesdriftthroughthecytoplasmandusuallycarryfoodmoleculesinsolution.Lysosomesarestructuressomewhatsimilarinappearancetovacuolesbutdenser.Theyappeartohaveadigestivefunction.Eachlysosomeisfi

60、lledwithdigestiveenzymesandencasedinamembrane.Lysosomesarebelievedtobreakdownfoodsubstancesbroughtintothecellbypinocytosis.IthasbeensuggestedthattheGolgicomplexplaysapartintheformationoflysosomes.在細(xì)胞質(zhì)內(nèi)游動的液泡一般是帶著食物分子的溶液。溶酶體是一種有點(diǎn)像液泡的結(jié)構(gòu)，但較稠。它是用來消化的。每個溶酶體的膜內(nèi)都是添裝著消化酶。我們認(rèn)為它是消化通過“胞飲”方式的大物質(zhì)。也認(rèn)為高爾基體對溶酶體的形成有關(guān)