PAGE1PAGE1UnitOneTHEPAROTIDGLANDANDITSRELATIONSTheparotidisthelargestofthesalivaryglands.Itliesbeneaththeskinonthesideofthefaceandissurroundedbyfasciawhichisthickestlaterallyandinferiorly.Extensionsofthisfasciadividetheglandintoaseriesoflobules.Theoutlineoftheglandisirregularandadaptedtoadjacentstructures-themandible,temporalbone,thezygomaticarchandthecartilageortheexternalear.Itisdivisibleintosuperficialanddeeplobes,connectedbyanisthmus.Theparotidglandoccupiesawedge-shapedspacewhichisboundedinfrontbytheramusofthemandibleanditsrelatedmuscles,themasseterandmedialpterygoid;behindbythesternomastoidandtheposteriorbellyofthedigastric.Mediallyitislimitedbythestyloidprocessanditsattachedmuscles,separatingthedeeppartoftheglandfromthestillmoredeeplyplacedinternaljugularveinandthesidewalloftheupperpartofthepharynx.1Theglandissurroundedbyasheathofcervicalfascia,amodifiedthickenedpartofthegeneralinvestinglayer,andthestructureswhichpassthroughtheglandpiercethisfascia.Theductofthegland(Stensen'sduct)appearsatitsanteriorborderandpassesforwardsacrossthemassetermuscleaboutoneinchbelowtheupperborderofthezygomaticarch.Itcanal-sobedescribedaslyingafinger'sbreadthbelowthezygomaticarch.Inrelationtosurfacefeatures,itisrepresentedbythemiddlethirdofthelinedrawnformthetragusoftheear,tothemidpointofaverticallineextendingfromthealaofthenosetotheredRangoonoftheupperlip.Attheanteriorborderofthemuscleitturnssharplyinwards,passingaroundthebuccalpadoffat,topiercethebuccinatormuscleandopenintothemouthcavity.Atbirththeorificeoftheductisoppositethefirstdeciduousmolarandtheductopeninggraduallychangesitspositionrelativetotheteethduringchildhoodduetogrowthofthedentalarches.Intheadultitisonapapillaoppositetotheuppersecondpermanentmolartooth.Theparotidglandwithitsductisanoutgrowthfromthemouthcavity.Growingbackwardsacrosstheramusofthemandibleandthecoveringmasssetermuscleitinvadestheretromandibuiarspace,whichhasalreadybeenoccupiedbythefacialnerve,externalcarotidarteryandposteriorfacialvein.Whenthisisremembered,itwillbeunderstoodhowthesestructuresappeartoliewithinthesubstanceoftheglandintheadult.Whenthedeeplobeisdissectedaway,theparotidbedisexposed.Itiscomposedofthefollowingstructures2:theexternalcarotidartery,thestyloidprocessanditsrelatedmuscles.viz.styloglossusstylopharyngeusandstylohyoid;theinternaljugularvein,theinternalcarotidartery;theglossopharyngeal,vagus,spinalaccessoryandhypoglossalnerves.Thefacialnerveenterstheposteromedialsurfaceoftheglandclosetotheupperpole,betweenthesuperficialanddeeplobes.Withintheglanditliesmoresuperficiallythantheotherstructures.Itusuallydividesintotwoparts,anupperbranchfromwhicharegivenoffthetemporalzygomaticandupperbuccalbranchesandalowerbranchfromwhicharisethelowerbuccal,mandibularandcervicalbranches.Theseterminalbranchesofthenerveappearonthefacealongtheanteriormarginoftheparotidglandasthisoverlapthemassetermuscles.Theexternalcarotidarterypiercesthefascialcapsuleoftheglandattheupperborderoftheposteriorbellyofthedigastricmuscleandentersthedeepsurfaceofthelowerpole.Justbeforeenteringtheglandsubstanceitgivesofftheposteriorauriculararterywhich,leavingthecapsuleofthegland,runsupwardsandbackwardsalongtheupperborderofthedigastricmuscle.Oneoftheterminalbranchesofthisarteryentersthestylomastoidforamenfromwhichthefacialnerveemerges.Withintheparotidglandtheexternalcarotidarterygivesoffsmalltwigstosupplytheglandsubstanceanddividesintoitsterminalbranches,thesuperficialtemporalarteryandthemaxillaryartery.Thesuperficialtemporalarteryemergesfromtheupperpoleoftheglandwiththeauriculotemporalnervelyingimmediatelybehindit,andcrossestherootofthezygomaticarchinfrontoftheexternalauditorymeatus.Themaxillaryarteryleavestheanteromedialsurfaceofthegland,usuallyrunningforashortdistancewithinthepterygoidlobe.Itpassesintothepterygoidregiondeeptotheramusofthemandible.Theretromandibularveinisformedwithinthecapsuleoftheglandandsometimeswithintheglandsubstance,bytheunionofthesuperficialtemporalandmaxillaryveins.Theposteriorfacialveinthenpassesthroughtheparotidglandbetweenthesuperficialbranchesofthefacialnerveandthemoredeeplyplacedexternalcarotidartery.Itdividesnearthelowerborderoftheglandtoappearatthedeepsurfaceofthelowerpoleastwobranches,theanteriorandposteriordivisionsofthevein.Theformerpiercestheglandcapsuletoenterthesubmandibularspace,whereitisjoinedbytheanteriorfacialveintoformthecommonfacialvein.3Thelatterleavestheposteriorpartoftheglandcapsuleand,onthesurfaceofthesternocleidomastoid,isjoinedbytheposteriorauricularveintoformtheexternaljugularvein.Lymphaticdrainagefromtheregionoftheparotidglandisintothedeepcervicallymphnodes,whichcommonlybecomeinvolvedwithextensionsofparotidtumors.Thepre-auricularnodesliesuperficialtothecapsuleoftheparotidglandandareseldominvolvedinpathologicconditionsofthegland.Theydrainintoachainofnodesalongtheexternaljugularvein.Deepnodesarefoundintheglandandinferiortoit.Aswellasdrainingtheglands,theyreceivelymphaticfromthenasopharynx,the.nose,palate,auditorytube,middleearandexternalacousticmeatus.Efferentvesselspasstonodesalongtheinternaljugularvein.Theauriculotemporalnervehasaveryshortbutimportantcoursethroughtheupperpoleoftheparotidgland(glenoidlobe)for,whilepassingthrough,itgivesoffsecretomotorfibrestothegland.Thesearederivedfromtheninthcranialnerve(glossopharyngeal)andpassviathetympanicplexus,lessersuperficialpetrosalnerve,andoticganglion,tojointheauriculotemporalnerve.Thesympatheticnervesupplyreachestheglandthroughtheperivasoularnerveplexusaroundtheexternalcarotidarteryaspostganglionicnervefibreswhosecellbodiesarelocatedinthesuperiorcervicalganglionofthesympatheticnervechain.Clinicalnotes,Becausethefacialnervepassesthroughanddividesinthesubstanceoftheparotidgland,itisatriskduringsurgeryoftheparotidregionforremovaloftumors.Damagetothenerveresultsinparalysisofmusclesofexpressiononthesamesideoftheface.Sometimessuchinjuriesareunavoidableduringsurgeryofthegland.Theparotidglandistheprimarysalivaryglandinvolvedintheacuteviraldisease,mumpsorparotitis.4Painfromtheswollenglandisseverebecauseitisinvestedbythedeepcervicalfasciathatdoesnotstretchreadily.Painoriginatingfromtheparotidglandisoftenreferredtotheear,templeortemporomandibularjointbytheauriculotemporalbranchofthetrigeminalnerve.Astone,orcalculus,lodgedintheparotidductisanothercauseofpainfulswelling,particu!arlyatmealtimesiftheductispartiallyblocked.Swellingsduetoinfectionorductobstructionhavetobedifferentiallydiagnosedfromparotidtumors,suchasthemixedparotidtumororpleomorphicadenoma,whichinvadestheparotidtissueandmaycauseafacialparalysis.Calculicanbedetectedonradiographsbecauseoftheircalciumsaltcontent,whichrendersthemopaquetoX-rays.Thedistributionofsalivaryductscanbedemonstratedbyinjectingradiopaquemediumintothemainductsandexaminingitsdistributionradiographically,aprocedurecalledasialogram.Sialogramsareparticularlyimportantforthedetectionandextentofsalivaryglandtumors.Theductsofthesublingualglandsaretoosmallforinjectionsofradiopaquesubstancestohaveanypracticalvalue.VOCABULARY1.parotid腮腺；腮腺的，耳下的2.fascia帶、筋膜3.cartilage軟骨4.laterally外側5.inferiorly下方6.divisible可分的，可分割的7.isthmus峽8.wedge楔、楔形物9.ramus支10.masseter咬肌11.medialpterygoid翼內肌12.internaljugularvein頸內靜脈13.sheath鞘、套14.invest包圍、給著衣；投資15.zygomaticarch顴弓16.breadth寬度、廣度17.tragus屏18.ala翅、翼19.buccalpadoffat頰脂墊20.orifice孔口、洞口、通氣口21.deciduous脫落的[解]乳牙(deciduousteeth)22.retromandibularspace下頜后間隙23.externalcarotidartery頸外動脈24.styloidprocess莖突25.viz.(拉丁文)即namely(通常讀作nan26.styloglossus莖突舌肌27.stylopharyngeus莖突咽肌28.stylohyoid莖突舌骨肌29.glossopharyngealnerve舌咽神經30.vagus迷走神經31.spinalaccessory脊付神經32.hypoglossal舌下的、舌下神經33.overlap重迭、迭蓋住34.belly腹35.digastricmuscle二腹肌36.posteriorauricularartery耳后動脈37.stylomastoidforamen莖乳孔38.twig纖細的分支39.auriculotemporalnerve耳顳神經40.externalauditorymeatus外聽道41.sternocleidomastoid胸鎖乳突肌42.tympanic鼓室的，鼓膜的43.plexus叢44.lessersuperficialpetrosalnerve巖淺小神經45.oticganglion耳神經節46.p