Chapter1Passage1HumanBodyInthispassageyouwilllearn:Classificationoforgansystems2.Structureandfunctionofeachorgansystem3.AssociatedmedicaltermsTounderstandthehumanbodyitisnecessarytounderstandhowitspartsareputtogetherandhowtheyfunction.Thestudyofthebody'sstructureiscalledanatomy;thestudyofthebody'sfunctionisknownasphysiology.Otherstudiesofhumanbodyincludebiology,cytology,embryology,histology,endocrinology,hematology,immunology,psychologyetc.認(rèn)識(shí)人體各部分的組成及其功能，關(guān)于認(rèn)識(shí)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)。其余研究人體的科學(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。Anatomistsfinditusefultodividethehumanbodyintotensystems,thatis,theskeletalsystem,themuscularsystem,thecirculatorysystem,therespiratorysystem,thedigestivesystem,theurinarysystem,theendocrinesystem,thenervoussystem,thereproductivesystemandtheskin.Theprincipalpartsofeachofthesesystemsaredescribedinthisarticle.解剖學(xué)家發(fā)現(xiàn)把整個(gè)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)以及感覺(jué)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,short,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(duì)軟組織及人體器官起到支持和保護(hù)作用，并牽動(dòng)骨胳肌，惹起各種運(yùn)動(dòng)。人體有206根骨頭。骨形態(tài)不一，有長(zhǎng)的、短、立方的、扁的及不規(guī)則的。很多長(zhǎng)骨里有一個(gè)內(nèi)層縫隙，里面充填著骨髓，這即是血細(xì)胞的制造場(chǎng)所。Ajointiswherebonesarejoinedtogether.Theconnectioncanbesoclosethatnomovementispossible,asisthecaseintheskull.Otherkindsofjointspermitmovement:eitherbackandforthinoneplane-aswiththehingejointoftheelbow-ormovementaroundasingleaxis-aswiththepivotjointthatpermitstheheadtorotate.Awiderangeofmovementispossiblewhentheball-shapedendofonebonefitsintoasocketattheendofanotherbone,astheydointheshoulderandhipjoints.關(guān)節(jié)把骨與骨連接起來(lái)。顱骨不能夠夠運(yùn)動(dòng)，是由于骨與骨之間的連接太親近。但其余的關(guān)節(jié)可同意活動(dòng)，如一個(gè)平面上的前后屈伸運(yùn)動(dòng)，如肘關(guān)節(jié)；或是繞軸心旋轉(zhuǎn)運(yùn)動(dòng)，如樞軸點(diǎn)同意頭部轉(zhuǎn)動(dòng)。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(yùn)動(dòng)（如肩關(guān)節(jié)、髖關(guān)節(jié)）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(zhì)。它是骨連接的保護(hù)、緩沖層。它把肋骨與胸骨連接起來(lái)，也是鼻腔與內(nèi)耳的結(jié)構(gòu)基礎(chǔ)。一個(gè)嬰兒的骨骼就是由軟骨組成，今后不斷生長(zhǎng)、1骨化，使嬰兒長(zhǎng)大成人。Themuscularsystemallowsthebodytomove,anditscontractionsproduceheat,whichhelpsmaintainaconstantbodytemperature.Striatedmusclescanbeconsciouslycontrolled.Theendsofthesemusclesareattachedtodifferentbonesbyconnectivetissuebandssothatwhenthemusclecontracts,onebonemovesinrelationtotheother.Thismakesitpossibletomovethewholebody,aswhenwalking,ortomovejustonepartofthebody,aswhenbendingafinger.Contractionsoftheheartandsmoothmusclesarenotunderconsciouscontrol.Smoothmusclesarefoundinthewallsoforganssuchasthestomachandtheintestinesandservetomovethecontentsoftheseorgansthroughthebody.肌肉系統(tǒng)使軀體運(yùn)動(dòng)，肌肉縮短產(chǎn)生的熱有助于維持一個(gè)恒定的體溫。人體能夠有意識(shí)地控制條紋肌。結(jié)締組織使肌肉尾端附著于不同樣樣的骨面上，所以當(dāng)肌肉縮短時(shí)，兩骨相互湊近而產(chǎn)生運(yùn)動(dòng)。這也就使整個(gè)人體能夠運(yùn)動(dòng)起來(lái)，如走路，運(yùn)動(dòng)軀體某個(gè)部位，如波折手指。心臟縮短和圓滑肌縮短就不是被意識(shí)所控制的。器官壁內(nèi)層的圓滑肌，如胃腸壁的圓滑肌把胃腸中的物質(zhì)運(yùn)送到全身。Thecirculatorysystem.Allpartsofthebodymusthavenourishmentandoxygeninordertofunctionandgrow,andtheirwasteproductsmustberemovedbeforetheyaccumulateandpoisonthebody.Thecirculatorysystemdistributesneededmaterialsandremovesunneededones.Itismadeupoftheheart,bloodvessels,andblood,whichtogethermakeupthecardiovascularsystem.Thebloodisalsopartofthebody'sdefensesystem.Ithasantibodiesandwhitebloodcellsthatprotectthebodyagainstforeigninvaders.循環(huán)系統(tǒng)：機(jī)體的全部部分需要營(yíng)養(yǎng)物質(zhì)和氧氣來(lái)使之發(fā)揮功能和生長(zhǎng)，也需要在這些器官所產(chǎn)生的廢物齊聚而危害生命從前將其除掉。循環(huán)系統(tǒng)運(yùn)送適用物質(zhì)，排泄廢物。心血管系統(tǒng)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)體防守系統(tǒng)的一個(gè)部分，血液中有抗體及白細(xì)胞來(lái)防范機(jī)體碰到外來(lái)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(lái)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。心臟縮短時(shí)，動(dòng)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,calledlymph,returnstotheheartbywayofanothersystemofchannels-thelymphvessels.Lymphnodesalongthesevesselsfilterthefluidbeforeitreenterstheblood.Thespleenisalargelymphaticorganthatfilterstheblood.淋巴系統(tǒng)也是循環(huán)系統(tǒng)的一個(gè)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，這類體液叫淋巴液，它是流經(jīng)另一個(gè)管道系統(tǒng)——淋巴管而回流人心臟。沿淋巴管的淋奉迎將淋巴液過(guò)濾，過(guò)濾后再回流人血液。脾是一個(gè)過(guò)濾血液的大淋巴器官。Therespiratorysystemtakesinoxygenfromtheairandexpelscarbondioxideandwatervapor.Airentersthenoseandmouthandtravelsthroughthelarynx,andtrachea.Thetracheadividestoentereachofthetwolungsandthendividesmorethan20timestoformaverylargenumberofsmallairspaces.Oxygenfromtheairentersthebloodthroughcapillariesinthewallsoftheseairspaces,andthebloodreleasecarbondioxideintotheairspacestobeexhaled.呼吸2系統(tǒng)從空氣中攝取氧氣，并將二氧化碳、水蒸氣排出體外。空氣經(jīng)鼻腔、口腔人喉管、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(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,foodandfluidsaretakenin,movedthroughthebody,andbrokendownintosmallmoleculesthatareabsorbedintothecirculatorysystem.Thisbreakdown,knownasdigestion,isbothamechanicalandachemicalprocess.消化系統(tǒng)是一個(gè)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(dòng)時(shí)，被分解成小分子物質(zhì)后再進(jìn)入循環(huán)系統(tǒng)。這類分解，即消化，是一個(gè)機(jī)械過(guò)程，也是一個(gè)化學(xué)過(guò)程。Foodentersthroughthemouth,wherechewingandsalivastarttobreakitupandmakeiteasiertoswallow.Next,thefoodtravelsdownthroughtheesophagustothestomach.Contractionsofthestomach'smuscularwallcontinuetobreakdownthefoodmechanically,andchemicaldigestioncontinueswhenacidandenzymesaresecretedintothestomachcavity.食品進(jìn)入口腔里，咀嚼和唾液開(kāi)始將食品粉碎，使之便于吞咽。接著，食品經(jīng)食管人胃。胃肌壁的縮短連續(xù)機(jī)械化地分解食品，而當(dāng)酸和酶分泌入胃腔時(shí)，化學(xué)性消化開(kāi)始。Theliquifiedfoodgraduallypassesintothesmallintestine.Inthefirstpartofthesmallintestine,calledtheduodenum,enzymesfromthepancreasareadded.Theseenzymescompletethechemicalbreakdownofthefood.Thedigestionoffatisaidedbybile,whichismadeintheliverandstoredinthegallbladder.Thesmallintestineofanadultisabout21feet(6.4meters)long.Mostofitslengthisdevotedtoabsorbingthenutrientsreleasedduringthesedigestiveactivities.液體化食品逐漸進(jìn)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(xué)分解。肝臟分泌的膽汁存儲(chǔ)在膽囊內(nèi)，膽汁有助于脂肪消化。一個(gè)成年人的小腸有21英尺（6.4米）長(zhǎng)。小腸的大多數(shù)腸段用來(lái)吸撤消化過(guò)程中釋放的營(yíng)養(yǎng)物質(zhì)。Theliquidremainderofthefoodentersthelargeintestine,orcolon,whichisabout12feet(3.7meters)long.Itismorethantwiceaswideasthesmallintestine.Inthelargeintestinemostofthefluidisabsorbed,andtherelativelydryresiduesareexpelled.液狀的節(jié)余食品進(jìn)入大腸，或結(jié)腸，它大概有12英尺（3.7米）長(zhǎng)。大腸是小腸的兩倍多寬。大多數(shù)液體在大腸內(nèi)被吸取，相對(duì)干化的節(jié)余物被排出體外。Theurinarysystemmaintainsnormallevelsofwaterandofcertainsmallmoleculessuchassodiumandpotassiuminthebody.Itdoesthisbypassingbloodthroughthekidneys,twoefficientfilteringorgansthatgetridofanyexcessofvariousmoleculesandconservethosemoleculesthatareinshortsupply.泌尿系統(tǒng)保持水分及體內(nèi)某些小分子物質(zhì)，如鈉、鉀的正常水平。身體是經(jīng)過(guò)讓’腎過(guò)濾血液來(lái)做到這一點(diǎn)的。腎是兩個(gè)有效的過(guò)濾器官，它濾出各種節(jié)余的小分子物質(zhì)，保留那些供應(yīng)不足的小分子物質(zhì)。Thefluidthatleavesthekidneys,knownasurine,travelsthroughatubecalledtheuretertothebladder.Thebladderholdstheurineuntilitisvoidedfromthebodythroughanothertube,theurethra.從腎流出的液體，即尿，經(jīng)過(guò)輸尿管人膀胱。膀胱起存儲(chǔ)尿液的作用，直到尿經(jīng)膀胱另一端的管道排出。Theendocrinesystem.Thetwosystemsthatcontrolbodyactivitiesaretheendocrinesystemandthenervoussystem.Theformerexertsitscontrolbymeansofchemicalmessengerscalled3hormones.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(dòng)的兩個(gè)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)分泌腺系統(tǒng)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(gè)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(duì)人體生長(zhǎng)、肝功能及性器官發(fā)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(gè)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(jī)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(jīng)系統(tǒng)——腦、脊髓及神經(jīng)，也調(diào)控機(jī)體活動(dòng)。腦的偏下部位控制著諸如呼吸、心跳、體溫、饑渴的基本活動(dòng)。而腦的偏上部位則是視覺(jué)、聽(tīng)覺(jué)、觸覺(jué)、嗅覺(jué)及味覺(jué)中心，也是指揮臂、腿隨意肌肉運(yùn)動(dòng)的地域。神經(jīng)系統(tǒng)更高級(jí)的功能是整合、辦理信息。Thebrainreceivesandsendsinformationbymeansofnerves,manyofwhichliepartlyinthespinalcord.Thespinalcordisprotectedbythespinalcolumn.Nervesenterandleavethespinalcordateachlevelofthebody,travelingtoandfromthearms,legs,andtrunk.Thesenervesbringinformationfromthevarioussenseorgans.Theinformationisprocessedbythebrain,andthenmessagesarecarriedbacktomusclesandglandsthroughoutthebody.腦經(jīng)過(guò)神經(jīng)收集并傳達(dá)信息，很多神經(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(jí)，神經(jīng)傳人、傳出脊髓，往返于臂、腿、軀體。這些神經(jīng)輸送來(lái)自各種感覺(jué)器官的信息。信息經(jīng)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(tǒng)不同樣樣。男性生殖系統(tǒng)產(chǎn)生、輸送、保持能存活的精子（男性性細(xì)胞）。它也分泌男性激素、睪酮，以此調(diào)理胡須、陰毛、深沉嗓音極其余成年男子身體發(fā)育的特色。Thefemaleproductivesystemisresponsibleforproducingandtransportingova(thefemale4sexcells),eliminatingovafromthebodywhentheyarenotfertilizedbysperm,nourishingandprovidingaplaceforgrowthofanembryowhenanovumisfertilizedbysperm,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(shí)，女性生殖系統(tǒng)培養(yǎng)、供應(yīng)胚胎生長(zhǎng)場(chǎng)所，并孕育再生兒。女性生殖系統(tǒng)也分泌女性性激素——雌激素和孕酮，以此調(diào)理乳房及其余成熟女性身體發(fā)育的特色。Theskinisacompletelayerthatprotectstheinnerstructuresofthebody,anditisthelargestofthebody'sorgans.Itkeepsoutforeignsubstancesandpreventsexcessivewaterevaporation.Thenervesintheskinprovidetactileinformation.Theskinalsohelpskeepthebody'stemperaturecloseto37°C,heatisconservedbyreducingbloodflowthroughtheskinorisexpendedbyincreasingbloodflowandbyevaporationofsweatfromtheskin.Hairandnailsareaccessorystructuresoftheskin.皮膚是保護(hù)肌體內(nèi)層結(jié)構(gòu)的圓滿層，也是機(jī)體的最大器官。皮膚防守外來(lái)侵襲，防范過(guò)多水分蒸發(fā)。皮膚上的神經(jīng)供應(yīng)觸覺(jué)信息。皮膚也能將體溫維持到98.6華氏度（約37攝氏度）。經(jīng)過(guò)皮膚的血流量降低時(shí)，熱量就被存儲(chǔ)起來(lái)，經(jīng)過(guò)皮膚的血流增加及汗液蒸發(fā)時(shí)，熱量就發(fā)散。頭發(fā)及指甲是皮膚的隸屬結(jié)構(gòu)。CellsandTissues細(xì)胞與組織Inthispassage,youwilllearn:1.Humanbodysystemsasawhole2.Vitalpartsofacell3.FourkindsoftissuesCellsareorganizedintotissues,andtissuesarearrangedintoorgans,whichinturnaregroupedintosystems.Eachbodysystemservesitsspecificfunctions.Bearinmindhoweverthatthebodyfunctionsasawholenosystemisindependentoftheothers.Theyworktogethertomaintainthebody’sstateofinternalstability,dtermehomeostasis.Nowlet’sbeginourdiscussionwithcells,thesmallestunitoflivingmatterthatcanexistbyitself.細(xì)胞組成組織，組織組成器官，器官又進(jìn)一步組成系統(tǒng)。人體的每個(gè)系統(tǒng)都有其特定功能，可是，請(qǐng)記住這里:機(jī)體是作為一個(gè)整體來(lái)發(fā)揮作用的，沒(méi)有哪個(gè)系統(tǒng)能夠獨(dú)立于其余系統(tǒng)而存在，是整系通通共同作用保持了機(jī)體內(nèi)部的牢固狀態(tài)，即體內(nèi)平衡。此刻，我們先議論細(xì)胞─能獨(dú)立存在活性物質(zhì)的最小單位。Thebodycanbestudiedfromitssimplesttoitsmostcomplexlevel,beginningwiththecell.Allbodyfunctionsresultfromtheactivitiesofbillionsofthespecializedcells.Someplantsandanimalsconsistofonlyasinglecell.Othersarecomposedofmanybillionsofcells.從細(xì)胞開(kāi)始，我們能夠從最簡(jiǎn)單到最復(fù)雜的水平來(lái)研究機(jī)體。全部人體的功能都來(lái)自億萬(wàn)個(gè)特定細(xì)胞活動(dòng)，有的動(dòng)植物僅由一個(gè)細(xì)胞組成，其余生物則由億萬(wàn)個(gè)細(xì)胞組成。Cellsexistinavarietyofshapesandsizes.Theymay,forexample,becube-shapedorflat.Scientistswhostudycellshavedeterminedthatasinglecellmaybeaslargeasatennisballorsosmallthatthousandswouldfitonthepointofaneedle.Theyolkofahen’seggisactuallyavlargecell.Bycontrast,bacteriaeachoneofwhichisatinycellareamongthesmallestcells.Regardlessofitsshapeorsize,everycellcontainsthe“machineryneeded”tomaintainlife.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。科學(xué)家的研究發(fā)現(xiàn)單獨(dú)一個(gè)細(xì)胞能夠像網(wǎng)球同樣的大小，或小到幾千個(gè)細(xì)胞才能恰巧填滿針頭。雞的5蛋黃是一個(gè)特別大的單細(xì)胞。渺小的細(xì)菌呢算是最小的細(xì)胞。無(wú)論是細(xì)胞大小或形狀的不同，每個(gè)細(xì)胞都有“需要存活的系統(tǒng)”。對(duì)每個(gè)正常的細(xì)胞，有效力的細(xì)胞，都存在很多問(wèn)題，能以致疾病。Thesizeofcellsisusuallymeasuredinmicrons.Amicronisamillionthofameter,andabout25,000micronsequaloneinch.Thesmallestbacteriaareabout0.2micronindiameter.Theaveragecellinthehumanbodyabouttenmicronsindiameterisaspeckbarelyvisiblewithouttheaidofamicroscope.細(xì)胞的大小是以“微米”為長(zhǎng)度單位。微米是一米的一百萬(wàn)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)胞的議論圓徑約十微米，肉眼勉強(qiáng)能夠看獲得，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)。在最渺小水平針對(duì)細(xì)胞的結(jié)構(gòu)及功能的研究成為分子生物學(xué)。Allcellsconsistofprotoplasm,the“l(fā)ivingjelly.The”protoplasmofatypicalcellformsthreevitalpartsthecellmembrane,thecytoplasm,andthenucleus.Themembraneenclosestheothercellstructures.Muchofthechemicalworkofthecellisdoneinthecytoplasm,whichsurroundsthenucleus.Thenucleus,enclosedbyitsownmembrane,isthecontrolcenterofthecell.(seeFigure1-1)全部細(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(gè)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)胞的其余結(jié)構(gòu)。大多數(shù)的化學(xué)反響都在細(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,alake,orastream.Formany-celledplantsandanimals,however,themediumispartoftheorganisminplants,thesap;inanimals,theblood.細(xì)胞只能存活在能供養(yǎng)分又能除掉廢物的液體媒介中。對(duì)單細(xì)胞生物來(lái)說(shuō)，這就是細(xì)胞外的液體，如：大海里、河里或水流中。在對(duì)多細(xì)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(dòng)物以血液的形式。Thecellmembraneissemipermeable,ordifferentiallypermeablesomesubstancescanpassthroughit,butotherscannot.Thischaracteristicenablesthecelltoadmitusefulsubstancesandtorejectharmfulsubstancesfromthesurroundingfluidaswellastoforceout,orexcretewasteproductsintothefluid.細(xì)胞膜是半浸透性或差異性的浸透膜，即某些物質(zhì)能浸透。這個(gè)特別性使細(xì)胞對(duì)細(xì)胞周圍只吸取了需要的物質(zhì)而除掉去有害的物質(zhì)，包括細(xì)胞內(nèi)的廢物經(jīng)過(guò)液體化后排出細(xì)胞外。Thecellmembraneisanextremelythinbuttoughbandofproteinandphospholipidmolecules.Phospholipidsarechemicalssimilartostoredfat.Ontheevidenceofelectronmicrographs,biologistsbelievethatithasporesthroughwhichcertainsmallmoleculespassintact.Substancesprobablypassthroughthecellmembraneinseveralways.Smallchamberslocatedonthecellmembranecalledcaveolaegatherchemicalsignalsandchannelthemintothecells.Thecaveolaemayalsohelpdistributeproteinsthroughoutthecell.Largemoleculesenterthecellbyaprocesscalleddiffusion,inwhichtheymaybedissolvedbysubstancesinthecellmembrane.Theycanthenthroughthemembranewithoutdifficulty.Somecellstakeinlarge6moleculesbymeansofpinocytosis.Inthisprocess,thecellmembraneformsapocketaroundlargemoleculesfloatingagainstit.Themolecule-and-fluid-filledpocketthenbreadsloosefromthemembranetobecomeabubblelikevacuole,andthevacuolethendriftsintothecytoplasm.Finally,thevacuolewallbreaksupandthemoleculesarereleasedintothecytoplasm.細(xì)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(chǔ)的脂肪的蛋白物質(zhì)。經(jīng)過(guò)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)圓滿能夠經(jīng)過(guò)。物質(zhì)可經(jīng)過(guò)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(hào)再傳到細(xì)胞內(nèi)。小穴還可能參于細(xì)胞蛋白的分配。大的分子可經(jīng)過(guò)“滲濾”進(jìn)入細(xì)胞內(nèi)，或被細(xì)胞膜內(nèi)體分解，使它們更簡(jiǎn)單的進(jìn)入細(xì)胞內(nèi)。有些細(xì)胞可經(jīng)過(guò)“胞飲”方式吞飲較大的物質(zhì)。這個(gè)過(guò)程是通過(guò)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.Itswatercontentvariesfromaminimumofabout65percenttoamaximumofabout95percent.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,dependingontheconcentrationofsolidsdispersedinthefluid.Whenthesolidcontentdecreases,thesestructuresseemtovanish.Changesinconcentrationalsoproduceanapparentsteamingofthecytoplasmfromplacetoplacewithinthecell.Thisoccurs,forexample,whenfoodmoleculesenterthecell.細(xì)胞質(zhì)可能是水性或糖漿性，依照散在細(xì)胞質(zhì)內(nèi)固體的濃度。當(dāng)固體成分濃度增加，膜狀和纖維狀結(jié)果在細(xì)胞質(zhì)顯出。而當(dāng)固體成分濃度減少時(shí)，膜狀和纖維狀的結(jié)構(gòu)就消失。濃度的變化還可以夠夠表現(xiàn)細(xì)胞質(zhì)內(nèi)局部流動(dòng)的變化。食品分子進(jìn)入時(shí)可見(jiàn)。Mostofthecell’sconstantworkofkeepingaliveisperformedinthecytoplasm.Herefoodmoleculesarechangedintothematerialneededforenergyandmaterialsforgrowthorstiffeningofthecellmembranearemanufacturesneededbytherestoftheorganism.Forexample,plantcellscontainingchlorophyllmanufactureglucoseaplantfoodfromcarbondioxideandwater.大多數(shù)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，食品物質(zhì)將被轉(zhuǎn)化成供應(yīng)細(xì)胞能量的資料和供應(yīng)細(xì)胞生長(zhǎng)的資料，或細(xì)胞膜的加強(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(duì)其余生物供應(yīng)食品的物質(zhì)。列如：植物葉綠素所產(chǎn)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(xì)胞質(zhì)能量變換的要點(diǎn)發(fā)生在錐狀形的線粒體。每個(gè)線粒體都有內(nèi)膜和外膜。像細(xì)胞膜同樣，線粒體的膜也是半浸透性。進(jìn)入線粒體的食品分子被氧化供應(yīng)出能量。Theendoplasmicreticulum,anetworkofmembranoustubes,runsthroughthecytoplasm.Intheopinionofsomebiologists,thisnetworkisacontinuousstructurethatbeginsatthecellmembrane,twiststhroughthecytoplasm,andendsatthemembranesurroundingthenucleus.Locatedalongtheendoplasmicreticulumaswellaselsewhereinthecytoplasmarenumerous7ribosomes.Thesetinygranulesconsistinpartofribonucleicacid(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，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)搬動(dòng)到高爾基體存儲(chǔ)，為了今后分泌所用。Vacuolesdriftthroughthecytoplasmandusuallycarryfoodmoleculesinsolution.Lysosomesarestructuressomewhatsimilarinappearancetovacuolesbutdenser.Theyappeartohaveadigestivefunction.Eachlysosomeisfilledwithdigestiveenzymesandencasedinamembrane.Lysosomesarebelievedtobreakdownfoodsubstancesbroughtintothecellbypinocytosis.IthasbeensuggestedthattheGolgicomplexplaysapartintheformationoflysosomes.在細(xì)胞質(zhì)內(nèi)游動(dòng)的液泡一般是帶著食品分子的溶液。溶酶體是一種有點(diǎn)像液泡的結(jié)構(gòu)，但較稠。它是用來(lái)消化的。每個(gè)溶酶體的膜內(nèi)都是添裝著消化酶。我們認(rèn)為它是消化經(jīng)過(guò)“胞飲”方式的大物質(zhì)。也認(rèn)為高爾基體對(duì)溶酶體的形成相關(guān)系。TheNucleus細(xì)胞核Nearthecenterofthecellisaroundishoroval-shapednucleus.Thenucleuscontrolsthegrowthanddivisionofthecell.Italsocontainsthestructuresthattransmithereditarytraits.細(xì)胞的中央，圓形或橢圓形的就是細(xì)胞核。細(xì)胞核控制細(xì)胞的生長(zhǎng)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(xì)胞核內(nèi)含有稱為“核質(zhì)（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(zhǎng)的基因系列所組成的，它是植物和動(dòng)物的遺傳信息?；驔Q定了細(xì)胞的特色。它是經(jīng)過(guò)調(diào)理核糖核酸，使核糖核酸產(chǎn)出特異的蛋白。Humancells,forexample,makeonlyproteinsuniquetohumanbeingsDNAstrandsareusuallytoothinlystrungouttobeseenwithanopticalmicroscope.Becausethestrandsarereadilystainedwithdyes,theyarecalledchromatin.Whenacellbeginstodivide,however,thechromatinthickensintotheformofchromosomes.列如：人的細(xì)胞，只產(chǎn)出人獨(dú)到擁有的蛋白。脫氧核糖核酸縷一般都很渺小過(guò)光學(xué)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(zhì)”。細(xì)胞分化過(guò)程中，染色體拾起變厚形成了“染色體”。Anucleusnotundergoingdivisionhasatleastonenucleolus.ThenucleoluscontainsaconcentrationofRNA.BiologiststhinkRNAismadeinitiallyinthenucleusaccordingtoaDNA“blueprint”andstoredthereuntilneededforproteinmanufacture細(xì)胞.核分化核仁不會(huì)減少，最少要有一個(gè)核仁。核仁含有豐富的核糖核酸。生物學(xué)家認(rèn)為核糖核酸本來(lái)在核仁里，根據(jù)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(dòng)物的細(xì)胞核的圓形結(jié)構(gòu)叫“中心體”，可見(jiàn)呈放射狀發(fā)散的星體。中心體內(nèi)含有一對(duì)棍狀結(jié)構(gòu)，稱為“中心?！?，一般都形成正確固定的角度。無(wú)法在植物細(xì)胞發(fā)現(xiàn)中心體和中心粒，但生物學(xué)家認(rèn)為植物應(yīng)該有存在近似功能的其余結(jié)構(gòu)。Tissues組織Cellsareorganizedintotissuesthatperformspecificfunctions.Thefourbasictissuetypesareasfollows:多細(xì)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(hù)著身體結(jié)構(gòu)和分清器官、導(dǎo)管和空腔。Connectivetissuessupportsandbindsbodystructures.Itcontainsfibersandothernonlivingmaterialbetweenthecells;includedarefattissues,cartilage,boneandblood.結(jié)締組:支柱和聯(lián)系著身體結(jié)構(gòu)。包括細(xì)胞之間的纖維和其余無(wú)生物結(jié)構(gòu)。包括脂肪組織、軟骨、骨頭和血液。Muscletissuescontractstoproducemovement.Thethreetypesare：skeletalorvoluntarymusclethatmovestheskeleton;thecardiacmuscleoftheheart;andthesmoothmusclethatformsthewallsoftheabdominalorgans.Cardiacandsmoothmusclecanfunctionwithoutconsciouscontrolandarethusdescribedasinvoluntarymuscle.肌肉組織:經(jīng)過(guò)整理來(lái)產(chǎn)生動(dòng)作。分為三種：骨骼肌，作用于一般骨骼搬動(dòng)。心計(jì)，心臟的肌肉。圓滑肌，形成胃腸道壁的肌肉。心計(jì)和圓滑肌是非意識(shí)性，不隨意性肌肉。Nervoustissue——makesupthebrain,spinalcord,andnerves.Itcoordinatesandcontrolsbodyresponsesbytransmittingelectricalimpulses.神經(jīng)組織:組成大腦、脊椎和神經(jīng)。它是經(jīng)過(guò)動(dòng)作電位來(lái)超空身體。Thesimplesttissuesaremembranes.Mucousmembranessecretethickfluidcalledmucusthatprotectsunderlyingtissues.Serousmembranessecreteathin,wateryfluid.Theylinebodycavitiesandcoverorgans.最簡(jiǎn)單的組織就是膜。粘液膜分泌出粘稠的膠液，起得組織保護(hù)作用。粘液組織分泌出較稀的粘液，起得身體導(dǎo)管的分界和覆蓋著各個(gè)器官。HumandiseasesInthispassageyouwilllearn:1.diseaseandpathology2.theclassificationofdiseases3.germs’invasionofthehumanbody4.thebody’defenseagainstinvasion5.thebody’simmunitytodiseasesThebriefsurveyofthehumanbodyinChapterOnehasgivenusaglimpseintotwodifferentstudiesthatareconsideredthefundamentalsofmedicalsciences,namelyanatomyandphysiology.However,thepictureisnotcompletewithoutconsideringpathology,thesciencethatdealswiththestructuralandfunctionalchangesproducedbythedisease.Infact,themodernapproachtothestudyofdisorderemphasizesthecloserelationshipofthepathologicalandphysiologicalaspectsandtheneedtounderstandthefundamentalsofeachintreatinganybodydiseases.第一章中，經(jīng)過(guò)對(duì)人體的概論，即解剖學(xué)與生理學(xué)，我們對(duì)兩種被認(rèn)為是醫(yī)學(xué)基礎(chǔ)的不同樣樣學(xué)科有了一個(gè)大概的印象?？墒侨羰俏覀儾豢紤]病理學(xué)，這門涉及由疾病帶來(lái)的結(jié)構(gòu)和功能變化的學(xué)科，上述的人體概論就不是圓滿的。實(shí)質(zhì)上，現(xiàn)代對(duì)疾病的研究方法重申了病理學(xué)與生理學(xué)方面的親近關(guān)系，重申了我們?cè)谥委熑魏稳梭w疾病方面需要認(rèn)識(shí)病9理學(xué)與生理學(xué)基礎(chǔ)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(shí)的一種狀態(tài)。每一種生物、植物和動(dòng)物，都會(huì)受制于疾病。比方，人類經(jīng)常被渺小的細(xì)菌所感染，可是，反過(guò)來(lái)說(shuō)，細(xì)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(yī)生能以此診斷疾病之所在。癥狀是病人自己就能覺(jué)察到的，比方，高燒、流血，或是悲傷。而征兆則是醫(yī)生能夠觀察到的，比方，血管擴(kuò)大或是體內(nèi)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(qū)內(nèi)侵襲很多人的疾病。當(dāng)它年復(fù)一年地侵襲同一社區(qū)，就成了一種地方病。急性病發(fā)生快，但病程短，舉個(gè)例子來(lái)說(shuō)，急性心臟病發(fā)生經(jīng)常沒(méi)有預(yù)兆，而且會(huì)很快致命。慢性病發(fā)生則慢，但病程有時(shí)會(huì)長(zhǎng)達(dá)幾年之久。風(fēng)濕熱正是由于發(fā)病慢、病程長(zhǎng)而成為一種慢性失調(diào)?。圆。?。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(lái)劃分，比方，傳生病也叫作可流傳的疾病，就是一種經(jīng)過(guò)咳嗽和打噴嚏造成的空氣小粒來(lái)流傳的疾病。極小的有機(jī)體，如，細(xì)菌和真菌能夠致傳生病。病毒和小蟲(chóng)子也不例外。無(wú)論病原領(lǐng)悟是什么樣，只要它存活于人體內(nèi)便能夠傳染給別人。有時(shí)，一個(gè)致病的有機(jī)體侵人人體后，該人卻沒(méi)有顯示帶病的癥狀。于是無(wú)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(diào)惹起的。這包括血管或10組織退化、異常細(xì)胞生成，以及異常的血液生成和血液循環(huán)。自然其中也包括胃、腸、內(nèi)分泌系統(tǒng)和泌尿生殖系統(tǒng)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(jīng)系統(tǒng)工作不造成的。Disabilityandillnessescanalsobeprovokedbypsychologicalandsocialfactors.Theseailmentsincludedrugaddiction,obesity,malnutrition,andpollution-causedhealthproblems.心理因素和社會(huì)因素也會(huì)惹起殘廢和疾病，這些病包括吸毒成性、肥胖、營(yíng)養(yǎng)不良和由污染造成的健康問(wèn)題。Furthermore,athousandormoreinheritablebirthdefectsresultfromalternationsingenepatterns.Sincetinygenesareresponsibleforproducingthemanychemicalsneededbythebody,missingorimproperlyoperatinggenescanseriouslyimpairhealth.Geneticdisordersthataffectbodychemistryarecalledinbornerrorsofmetabolism.Someformsofmentalretardationarehereditary.而且，有上千種以致為數(shù)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(fù)責(zé)著生產(chǎn)很多身體所需的化學(xué)物質(zhì)，它的拋棄或是工作狀態(tài)不良都會(huì)嚴(yán)重?fù)p害健康。因基因失調(diào)而被影響了的身體化學(xué)反響被稱之為先天性代謝失調(diào)。一些眢力發(fā)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(gè)有很多其余生物競(jìng)爭(zhēng)食品和求得繁衍的世界里。很多致病的有機(jī)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(xì)胞和組織液來(lái)供它們自己的需求。一般來(lái)講，身體防守系統(tǒng)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(jī)體能經(jīng)過(guò)多種方式進(jìn)入身體。它們的一些是被呼吸進(jìn)體內(nèi)的，比方那些惹起一般感冒、肺炎和肺結(jié)核的病菌；其余的是經(jīng)過(guò)人體性接觸進(jìn)入的，比方那些惹起花柳病的病原體；還有其余的一些是經(jīng)過(guò)污染了的食品、水或器皿進(jìn)入體內(nèi)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(chóng)作為媒介動(dòng)物或是病原攜帶者會(huì)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(jīng)過(guò)蚊子、虱子或其余媒介動(dòng)物的叮咬，病菌也可能進(jìn)入體內(nèi)。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(gè)11健康的身體有很多屏障來(lái)抵擋感染的發(fā)生。覆蓋在體表也許器官?gòu)埧谔幍钠つw和粘膜能在很大程度上抵擋細(xì)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(duì)感染的抵擋力就會(huì)下降。在一些病情較輕的病例中，疥子和小膿胞可能會(huì)發(fā)生。在病情較重的病例中，身體的大面積地域則可能會(huì)被感染。Breathingpassagesareespeciallyvulnerabletoinfection.Fortunately,theyarelinedwithmucus-secretingcellsthattraptinyorganismsanddustparticles.Also,minutehairscalledcilialinethebreathingpassages,wavelikeafieldofwheat,andgentlysweepmatteroutoftherespiratoryt