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THE PTERYGOPALATINEFOSSA MAXILLARYNERVE EAR VESTIBULOCOCHLEARNERVE CNVIII 1 THEPTERYGOPALATINEFOSSA 2 THEPTERYGOPALATINEFOSSA THEPTERYGOPALATINEFOSSA Thepterygopala/nefossaliesbetween: • thepterygoidprocessofthesphenoidposteriorlyand • theroundedposterioraspectofthemaxillaanteriorly. Thepterygopala/nefossaisanirregularlyshapedspaceposteriorto themaxillaandinferioranddeeptothezygoma/carch. Becauseofitsstrategicloca/on,thepterygopala/nefossaisamajor siteofdistribu/onforthemaxillarynerveV2andfortheterminal partofthemaxillaryartery. 3 THEPTERYGOPALATINEFOSSA THEPTERYGOPALATINEFOSSA BOUNDARIESOFTHEPTERYGOPALATINEFOSSA: Anterior: Posteriorsurfaceofmaxilla Posterior:Lateralplateofpterygoidprocessandgreaterwingof sphenoid Superior:thebodyofthesphenoid,infratemporalsurfaceofthe greaterwingofthesphenoidandorbitalsurfaceofthe pala/nebone Inferior: PyramidalprocessofthepalaLnebone Medial: PerpendicularplateofpalaLnebone Lateral: Openthroughpterygomaxillaryfissure 4 THEPTERYGOPALATINEFOSSA THEPTERYGOPALATINEFOSSA Anteriorly,thepterygopala/nefossaiscloselyrelatedtotheorbit throughtheinferiororbitalfissure Medially,itisrelatedtothenasalcavitythroughthesphenopalaLne foramen Inferiorly,itisrelatedtotheoralregionthroughthegreaterand lesserpalaLneforamina Laterally,itisrelatedtotheinfratemporalfossathroughthe pterygomaxillaryfissure Posterosuperiorly,itisrelatedtothemiddlecranialfossathrough theforamenrotundumandpterygoidcanal. 5 THEPTERYGOPALATINEFOSSA 6 THEPTERYGOPALATINEFOSSA THEPTERYGOPALATINEFOSSA-OPENNINGS PTERYGOMAXILLARYFISSURETHEINFRATEMPORALFOSSA SPHENOPALATINEFORAMEN THENASALCAVITY INFERIORORBITALFISSURE THEORBIT PALATINECANAL THEHARDANDTHESOFTPALATE FORAMENROTUNDUMTHEMIDDLECRANIALFOSSA PTERYGOIDCANAL THEFORAMENLACERUM PHARYNGEALCANAL THENASOPHARYNX 7 THEPTERYGOPALATINEFOSSA THEPTERYGOPALATINEFOSSA ThepterygopalaLnefossacontains: • themaxillarynerveV2 • thepterygopalaLneganglion • thenerveofthepterygoidcanal,and • thethirdorpterygopalaLnepartofthemaxillaryarteryandits branches 8 THEPTERYGOPALATINEFOSSA THEPTERYGOPALATINEFOSSA LymphaLcdrainageofthetemporal,infratemporal,and pterygopala/nefossaeistoregionallymphnodes-thesuperficial nodesatthejunc/onoftheheadandneckandthesuperiordeep cervicalnodesalongthecaro/dsheath. 9 THEMAXILLARYNERVE THEMAXILLARYNERVE Themainnervesassociatedwiththetemporal,infratemporal,and pterygopala/nefossaearebranchesofthemaxillaryV2and mandibularV3nerves,whicharedivisionsofthetrigeminalnerveCNV ThemaxillarynerveV2leavesthemiddlecranialfossathroughthe foramenrotundumandentersthepterygopalaLnefossa. Itisasensorynervewithnomotorcomponent,anditsbranches providesensa/ontothemidsec/onoftheface: • lowerpartoftheorbit, • nose, • upperpartofthemouth,and • cheek 10 THEMAXILLARYNERVE THEMAXILLARYNERVE A^erenteringthepterygopala/nefossa,themaxillarynerveV2gives riseto: • thezygomaLcnerve, • twopterygopalaLnenerves,and • theposteriorsuperioralveolarnerves(whichsupplythemaxillary sinusandmaxillarymolars). ThezygomaLcnervefurtherdividesinto: • thezygomaLcofacialand • thezygomaLcotemporalnerves, whichprovidesensa/ontotherespec/veregionsoftheupperlateral aspectoftheface ThepterygopalaLnenervessuspendthepterygopalaLneganglion withinthepterygopala/nefossa. Theposteriorsuperioralveolarnervessuppliesthemaxillarysinus andmaxillarymolars. 11 THEMAXILLARYNERVE THEMAXILLARYNERVE Thisganglionreceivesautonomicinnerva/onfromthenerveofthe pterygoidcanal,whichisacombina/onoftwonerves: • theparasympatheLcroot(abranchofthefacialnerve[VII]) • thesympatheLcroot(whichoriginatesfromthesuperiorcervical ganglion) NervesfromthepterygopalaLneganglioncarryparasympathe/c andsympathe/cfibersandsensorynervesfromthemaxillarynerve V2tosupply: • thelacrimalglandand • glandsinthenasaland • upperoropharyngealregions. 12 THEMAXILLARYNERVE THEMAXILLARYNERVE ThemaxillarynerveV2leavesthepterygopala/nefossathroughthe inferiororbitalfissure. Fromthispointitisreferredtoastheinfra-orbitalnerve Itenterstheorbitandpassesanteriorlywithintheinfra-orbitalgroove andthenwithintheinfra-orbitalcanalun/litemergesontotheface approximately1cminferiortotheinferiororbitalrim Theinfra-orbitalnerveprovidessensa/onto: • theskinoftheupperlip, • lowereyelid, • cheek,and • lateralpartofthenose. 13 THEPTERYGOPALATINEGANGLION THEPTERYGOPALATINEGANGLION Isthelargestofthefourparasympathe/cgangliaintheheadandis formedbythecellbodiesofthepostganglionicneuronsassociated withpreganglionicparasympathe/cfibersofthefacialnerve[VII] carriedbythegreaterpetrosalnerveandthenerveofthepterygoid canal. Themaxillarynervegivesoffthetwoganglionicbranchestothe pterygopala/neganglion(sensoryrootsofthepterygopala/ne ganglion)thatsuspendtheparasympathe/cpterygopala/neganglion inthesuperiorpartofthepterygopala/nefossa 14 THEPTERYGOPALATINEGANGLION THEPTERYGOPALATINEGANGLION 3setsofnervefiberstravelthroughthepterygopala/neganglion: • Generalsensoryfibersfromthemaxillaryn.(withoutsynapsing!) Thepterygopala/nenervesconveygeneralsensoryfibersofthemaxillary nerve,whichpassthroughthepterygopala/neganglionwithoutsynapsingto supplythenose,palate,andpharynx • ThedeeppetrosalnerveisasympatheLcnervearisingfromtheinternal caro/dplexusasthearteryexitsthecaro/dcanal. Itconveyspostsynap/cfibersfromnervecellbodiesinthesuperiorcervical sympathe/cgangliontothepterygopala/neganglionbyjoiningthenerveto thepterygoidcanal • PreganglionicparasympatheLcfiberscarriedtothepterygopala/ne ganglionviathevidiann.andformedbysynapsinginthepterygopala/ne ganglionwiththepostganglionicparasympathe/cfibers Theparasympathe/cfiberstothepterygopala/neganglioncomefromthe facialnerveVIIbywayofitsfirstbranch,thegreaterpetrosalnerve 15 THEPTERYGOPALATINEGANGLION THEPTERYGOPALATINEGANGLION Allbranchesarisingfromthepterygopala/neganglioncarrythese3 setsoffiberstotheareaswheretheyterminate. Thesenervesofthemaxillarydivisiontravelthroughthe pterygopala/neganglion: • nasopala/nen. • posteriorsuperiornasaln. • greaterpala/nen. • lesserpala/nen. • pharyngealn. Thisganglionreceivesautonomicinnerva/onfromthenerveofthe pterygoidcanal,whichisacombina/onoftwonerves: •theparasympatheLcroot-abranchofthefacialnerveCNVII •thesympatheLcroot-originatesfromthesuperiorcervicalganglion 16 THEPTERYGOPALATINEGANGLION THEPTERYGOPALATINEGANGLION Themajorityofthe‘branches’oftheganglionareprimarilysensory branchesofthemaxillarynerve.Thustheypassthroughtheganglion withoutsynapsingandenterthemaxillarynervethroughitsganglionic branches;theyconveysomeparasympathe/cfibrestothepala/ne, pharyngealandnasalmucousglands. Generalsensoryfibresdes/nedfordistribu/onviaorbital, nasopala/ne,superioralveolar,pala/neandpharyngealbranchesof themaxillarydivisionofthetrigeminalnerverunthroughtheganglion withoutsynapsing. 17 THEPTERYGOPALATINEGANGLION THEPTERYGOPALATINEGANGLION Preganglionicparasympathe/cfibresdes/nedforthepterygopala/ne ganglionrunini/allyinthegreaterpetrosalbranchofthefacialnerve, andtheninthenerveofthepterygoidcanal(Vidiannerve),a^erthe greaterpetrosaluniteswiththedeeppetrosalnerve. Postganglionicparasympathe/cfibresleavetheganglion;somemay jointhemaxillarynerveviaaganglionicbranchandthentravelviathe zygoma/candzygoma/cotemporalbranchesofthemaxillarynerveto thelacrimalgland,butmostarethoughttotravelbyorbitalbranches tothegland Postganglionicsympathe/cfibrespassthroughtheganglionwithout synapsingandsupplybloodvesselsandorbitalis. 18 THEEXTERNALEAR THEEAR Theauricleissupportedbycar/lageandiscoveredbyskin.The externalauditorymeatusisneartheanteriormarginoftheauricle. Theauriculotemporalnerve,abranchofCNV3,suppliestheskinof theauricleanteriortotheexternalacous/cmeatus Minorcontribu/onsofembryologicalsignificancearemadetotheskin oftheconchaanditseminenceby: • thevagusCNXand • thefacialnervesCNVII. 19 THEEXTERNALEAR THEEAR Thelympha/cdrainageoftheauricleisasfollows: • thelateralsurfaceofthesuperiorhalfoftheauricledrainstothe superficialparo/dlymphnodes • thecranialsurfaceofthesuperiorhalfoftheauricledrainstothe mastoidlymphnodesanddeepcervicallymphnodes; • theremainderoftheauricle,includingthelobule,drainsintothe superficialcervicallymphnodes. 20 THEEXTERNALEAR THEEAR THETYMPANICMEMBRANE Thetympanicmembrane,approximately1cmindiameter,isathin, ovalsemitransparentmembraneatthemedialendoftheexternal acous/cmeatus. Thetympanicmembraneformsapar//onbetweenthemeatusofthe externalearandthetympaniccavityofthemiddleear. Viewedthroughanotoscope,thetympanicmembranehasaconcavity towardtheexternalacous/cmeatuswithashallow,cone-likecentral depression,thepeakofwhichistheumbo. Superiortothelateralprocessofthemalleus(oneofthesmallear bones,orauditoryossicles,ofthemiddleear),themembraneisthin andiscalledtheflaccidpart. Itlackstheradialandcircularfiberspresentintheremainderofthe membrane,calledthetensepart. 21 THEEXTERNALEAR THEEAR THETYMPANICMEMBRANE • Theexternalsurfaceofthetympanicmembraneissuppliedmainly bytheauriculotemporalnerve,abranchofCNV3 • Someinnerva/onissuppliedbyasmallauricularbranchofthe vagus(CNX). • Theinternalsurfaceofthetympanicmembraneissuppliedbythe glossopharyngealnerve(CNIX). 22 THEMIDDLEEAR THEMIDDLEEAR Thecontentsofthemiddleeararethe: • auditoryossicles(malleus,incus,andstapes) • stapediusandtensortympanimuscles • chordatympaninerve,abranchofCNVII • tympanicplexusofnerves 23 THETYMPANICCAVITY THEMIDDLEEAR THE6WALLS 1.Thetegmentalwall(roof)isformedbyathinplateofbone,the tegmentympani,whichseparatesthetympaniccavityfromthedura materonthefloorofthemiddlecranialfossa. 2.Thejugularwall(floor)isformedbyalayerofbonethatseparates thetympaniccavityfromthesuperiorbulboftheinternaljugularvein. 3.Themembranouswall(lateralwall)isformedalmosten/relyby thepeakedconvexityofthetympanicmembrane;superiorlyitis formedbythelateralbonywalloftheepitympanicrecess.Thehandle ofthemalleusisakachedtothetympanicmembrane,anditshead extendsintotheepitympanicrecess. 24 THEMIDDLEEAR THETYMPANICCAVITY THE6WALLS 4.Thelabyrinthinewall(medialwall)separatesthetympaniccavity fromtheinternalear.Italsofeaturesthepromontoryofthe labyrinthinewall,formedbytheini/alpart(basalturn)ofthecochlea, andtheovalandroundwindows,which,inadrycranium, communicatewiththeinternalear. 5.Themastoidwall(posteriorwall)featuresanopeninginitssuperior part,theaditustothemastoidantrum,connec/ngthetympaniccavity tothemastoidcells;thecanalforthefacialnervedescendsbetween theposteriorwallandtheantrum,medialtotheaditus. 6.TheanteriorcaroLdwallseparatesthetympaniccavityfromthe caro/dcanal;superiorly,ithastheopeningofthepharyngotympanic tubeandthecanalforthetensortympani. 25 THETYMPANICCAVITY THEMIDDLEEAR RELATIONSHIPS 1.Thetegmentalwall(roof)-middlecranialfossaandtemporallobe 2.Thejugularwall(floor)-bulbofinternaljugularvein 3.Themembranouswall(lateralwall)-tympanicmembraneand epitympanicrecess 4.Thelabyrinthinewall(medialwall)-innerear,facialnerve[VII] 5.Themastoidwall(posteriorwall)-mastoidantrum,facialnerve [VII] 6.TheanteriorcaroLdwall-pharyngotympanictubeandinternal caro/dartery 26 THETYMPANICCAVITY THEMIDDLEEAR INNERVATION Thetympaniccavitycontainsthetympanicplexusandthefacialnerve. Branchesfromtheplexusandthefacialnervesupplystructureswithin thetympaniccavitybutalsoleavethecavitytosupplystructureson theface. 27 THEPHARYNGOTYMPANICTUBE THEMIDDLEEAR Thepharyngotympanictubeconnectsthetympaniccavity(anterior wall)tothenasopharynx,whereitopensposteriortotheinferiornasal meatus Itallowstheairpressureoneithersideofthetympanicmembraneto equalize. isopenedbytheexpandinggirthofthebellyofthelevatorvelipala/ni asitcontractslongitudinally,pushingagainstonewallwhilethetensor velipala/nipullsontheother Thenervesofthepharyngotympanictubearisefromthetympanic plexuswhichisformedbyfibersoftheglossopharyngealnerve(CNIX). Anteriorly,thetubealsoreceivesfibersfromthepterygopala/ne ganglion. 28 THEAUDITORYOSSICLES THEMIDDLEEAR Thebonesofthemiddleearconsistof: • themalleus, • incus,and • stapes Theseossiclesarethefirstbonestobefullyossifiedduring developmentandareessen/allymatureatbirth, unlikeotherbones,theylackasurroundinglayerofosteogenic periosteum Theyformanosseouschainofthreemobileossiclesacrossthemiddle earfrom: • thetympanicmembrane • totheovalwindowoftheinternalear 29 THEAUDITORYOSSICLES THEMIDDLEEAR transferssoundwavesacrossthetympaniccavityfromthetympanic membranetothefenestraves/buliofthebonylabyrinth. Themalleusisakachedtothetympanicmembrane,andthebase (footplate)ofthestapesisakachedtotherimofthefenestraves/buli. Theincusissuspendedbetweenthemandar/culateswithbothbones. 30 THEAUDITORYOSSICLES-MALLEUS THEMIDDLEEAR MALLEUS-iden/fiablepartsinclude: • theheadofmalleus • neckofmalleus • anteriorandlateralprocesses • handleofmalleus MALLEUS Theheadofthemalleusar/culateswiththeincus;thetendonofthe tensortympaniinsertsintoitshandleneartheneck. MALLEUS Themalleusfunc/onsasalever,withthelongerofitstwoprocesses anditshandleakachedtothetympanicmembrane. MALLEUS Thechordatympaninervecrossesthemedialsurfaceoftheneckofthe malleus. 31 THEAUDITORYOSSICLES-INCUS THEMIDDLEEAR INCUS islocatedbetweenthemalleusandthestapes. Itconsistsof: • thebodyofincusand • thelongandshortlimbs INCUS Theenlargedbodyofincusar/culateswiththeheadofmalleusandis intheepitympanicrecess. INCUS Thelonglimbextendsdownwardfromthebody,parallelingthehandle ofthemalleus,andendsbybendingmediallytoar/culatewiththe stapes. 32 THEAUDITORYOSSICLES-STAPES THEMIDDLEEAR STAPES Thestapesisthemostmedialboneintheosseouschainandis akachedtotheovalwindow. consistsof: • theheadofstapes • anteriorandposteriorlimbs • thebaseofstapes STAPES Theheadofstapesisdirectedlaterallyandar/culateswiththelong processoftheincus. STAPES Thebaseofstapesfitsintotheovalwindowonthelabyrinthinewallof themiddleear. 33 THEMIDDLEEAR THEMUSCLESASSOCIATEDWITHTHEOSSICLES Twomusclesareassociatedwiththebonyossiclesofthemiddleear: • thetensortympani • thestapedius 34 THEMIDDLEEAR THEMUSCLESASSOCIATEDWITHTHEOSSICLES TENSORTYMPANI ORIGIN:car/laginouspartof pharyngotympanictube,greater wingofsphenoid,itsownbony canal INSERTION:upperpartofhandle ofmalleus TENSORTYMPANI INNERVATION:branchfrommandibularnerveV3 TENSORTYMPANI FUNCTION:contrac/onpullshandleofmalleusmedially,tensing tympanicmembrane 35 THEMIDDLEEAR THEMUSCLESASSOCIATEDWITHTHEOSSICLES STAPEDIUS ORIGIN:akachedtoinsideof pyramidaleminence INSERTION:neckofstapes STAPEDIUS INNERVATION:branchoffacialnerveVII 36 THEMIDDLEEAR THEINNERVATIONOFTHEMIDDLEEAR Thetympanicplexusinnervatesthemucousmembraneliningthewalls andcontentsofthemiddleear,whichincludesthemastoidareaand thepharyngotympanictube. Thetympanicplexusisformedby: • thetympanicnerve,abranchoftheglossopharyngealnerve[IX],and • frombranchesoftheinternalcaroLdplexus. Branchesfromthetympanicplexussupplythemucousmembranesof themiddleear,includingthepharyngotympanictubeandthemastoid area. Thetympanicplexusalsogivesoffamajorbranch(thelesserpetrosal nerve),whichsuppliespreganglionicparasympathe/cfibers totheo/cganglion 37 THEINTERNALEAR THEINTERNALEAR Theinternalearconsistsof: • aseriesofbonycavi/es-thebonylabyrinthand • membranousductsandsacs-themembranouslabyrinthwithin thesecavi/es. Allthesestructuresareinthepetrouspartofthetemporalbone betweenthemiddleearlaterallyandtheinternalacous/cmeatus medially 38 THEINTERNALEAR THEBONYLABYRINTH Thebonylabyrinthconsistsof: • thevesLbule • threesemicircularcanals • thecochlea Thebonycavi/esarelinedwithperiosteumandcontainaclearfluid theperilymph 39 THEINTERNALEAR THEBONYLABYRINTH Thebonylabyrinthisthefluid-filledspace,whichissurroundedbythe o/ccapsule,andisrepresentedbyacastoftheo/ccapsulea^er removalofthesurroundingbone. ThevesLbularaqueductleavestheves/bule,andpassesthroughthe temporalbonetoopenontheposteriorsurfaceofthepetrouspartof thetemporalbone. 40 THEINTERNALEAR THECOCHLEA Thecochleaistheshell-shapedpartofthebonylabyrinththatcontains thecochlearduct,thepartoftheinternalearconcernedwithhearing. Thecochleaisabonystructurethattwistsonitselftwoandone-halfto twoandthree-quarter/mesaroundacentralcolumnofbone, themodiolus Themodioluscontainscanalsforbloodvesselsandfordistribu/onof thebranchesofthecochlearnerve. Thisarrangementproducesacone-shapedstructurewithabaseof cochleathatfacesposteromediallyandanapexthatfaces anterolaterally 41 THEINTERNALEAR THECOCHLEA Thisposi/onsthewidebaseofthemodiolusneartheinternalacous/c meatus,whereitisenteredbybranchesofthecochlearpartofthe ves/bulocochlearnerve[VIII]. Extendinglaterallythroughoutthelengthofthemodiolusisathin laminaofbone-thelaminaofmodiolusorspirallamina Circlingaroundthemodiolus,andheldinacentralposi/onbyits akachmenttothelaminaofmodiolus,isthecochlearduct,whichisa componentofthemembranouslabyrinth. 42 THEINTERNALEAR THECOCHLEA Akachedperipherallytotheouterwallofthecochlea,thecochlear ductcreatestwocanals-thescalavesLbuliandthescalatympani ThescalavesLbuliandthescalatympaniarecon/nuousattheapex throughanarrowslitthehelicotrema ThescalavesLbuliiscon/nuouswiththeves/bule. Thescalatympaniisseparatedfromthemiddleearbythesecondary tympanicmembranecoveringtheroundwindow Neartheroundwindowisasmallchannelthecochlearcanaliculus. Itprovidesaconnec/onbetweentheperilymph-containingcochlea andthesubarachnoidspace. 43 THEINTERNALEAR THEMEMBRANOUSLABYRINTH Themembranouslabyrinthisacon/nuoussystemofductsandsacs withinthebonylabyrinth Itisfilledwithendolymphandseparatedfromtheperiosteumthat coversthewallsofthebonylabyrinthbyperilymph Themembranouslabyrinth,composedoftwodivisions: • theves/bularlabyrinth • thecochlearlabyrinth 44 THEINTERNALEAR THEMEMBRANOUSLABYRINTH Consis/ngoftwosacs: • theutricle • thesaccule andfourducts: • thethreesemicircularducts • thecochlearduct Theves/bularlabyrinthandthecochlearlabyrinth,consistsofmore partsthandoesthebonylabyrinth: • vesLbularlabyrinth:utricleandsaccule,twosmallcommunica/ng sacsintheves/buleofthebonylabyrinth. • threesemicircularductsinthesemicircularcanals. • cochlearlabyrinth:cochlearductinthecochlea. 45 THEINTERNALEAR THEMEMBRANOUSLABYRINTH Thesemicircularductsopenintotheutriclethroughfiveopenings, reflec/veofthewaythesurroundingsemicircularcanalsopen intotheves/bule. Theutriclecommunicateswiththesacculethroughthe utriculosaccularduct,fromwhichtheendolympha/cductarises Thesacculeiscon/nuouswiththecochlearductthroughtheductus reuniens,auni/ngduct. 46 THEINTERNALEAR THEMEMBRANOUSLABYRINTH ThereceptorsforauditoryandvesLbularfuncLonarelocatedwithin themembranouslabyrinth Theutricleandsacculehavespecializedareasofsensoryepithelium calledmaculae. Thehaircellsinthemaculaeareinnervatedbyfibersoftheves/bular divisionoftheves/bulocochlearnerve. Inthemaculae,theweightoftheotoconialcrystalscreatesagravita/onal pullontheotoconialmembraneandthusonthestereociliarybundlesof thesensorycellsthatareinsertedintoitsbase.Becauseofthis,theyare abletodetectthesta/corienta/onoftheheadwithrespecttogravity. 47 THEINTERNALEAR THEMEMBRANOUSLABYRINTH Theprimarysensoryneuronsareintheves/bularganglia,whicharein theinternalacous/cmeatus. Fluidslocatedinthemembranouslabyrinth(endolymph)andosseous labyrinth(perilymph)s/mulatetheauditoryandves/bularreceptors 48 THEINTERNALEAR THEMEMBRANOUSLABYRINTH-SEMICIRCULARDUCTS Eachsemicircularducthasanampullaatoneendcontainingasensory area,theampullarycrest Thehaircellsofthecrests,likethoseofthemaculae,s/mulateprimary sensoryneurons,whosecellbodiesareintheves/bularganglia. 49 THEINTERNALEAR THEMEMBRANOUSLABYRINTH-COCHLEARDUCT Thecochlearductisaspiraltubethatrunswithinthebonycochlea Theductisfirmlysuspendedacrossthecochlearcanalbetweenthe spiralligamentontheexternalwallofthecochlearcanalandthe osseousspirallaminaofthemodiolus. Theroofofthecochlearductisformedbytheves/bularmembrane. Theflooroftheductisalsoformedbypartoftheduct,thebasilar membrane,plustheouteredgeoftheosseousspirallamina. 50 THEINTERNALEAR THEMEMBRANOUSLABYRINTH-COCHLEARDUCT Thereceptorofauditorys/muliisthespiralorganofCorL,situatedon thebasilarmembrane.Itisoverlaidbythegela/noustectorial membrane. Theorganiss/mulatedtorespondbydeforma/onofthecochlearduct inducedbythehydraulicpressurewavesintheperilymph,which ascendanddescendinthesurroundingscalaeves/buliandtympani. 51 THEEAR ANATOMYOFHEARING Wavesofhydraulicpressurecreatedintheperilymphoftheves/bule bythevibra/onsofthebaseofthestapesascendtotheapexofthe cochleabyonechannel,thescalaves/buli Thepressurewavesthenpassthroughthehelicotremaanddescend backtothebasalturnofthecochleabytheotherchannel,thescala tympani. Here,thepressurewavesagainbecomevibra/ons,this/meofthe secondarytympanicmembraneoftheroundwindow,andtheenergy ini/allyreceivedbythe(primary)tympanicmembraneisfinally dissipatedintotheairofthetympaniccavity. 52 THEEAR INTERNALACOUSTICMEATUS TheinternalacousLcmeatusisanarrowcanalthatrunslaterallyfor approximately1cmwithinthepetrouspartofthetemporalbone Throughtheperforatedplateoftemporalbonepassthefacialnerve (CNVII),theves/bulocochlearnerve(CNVIII)anditsdivisions,and bloodvessels. 53 THEEAR THEFACIALNERVE Thefacialnerveconsistsofintracranial(cisternal),intratemporaland extratemporalpor/ons. Theintratemporalpor/onisfurtherdividedinto: • meatal, • labyrinthine, • tympanic(horizontal) • mastoid(ver/cal) segments 54 THEEAR THEFACIALNERVE ThemeatalporLonenterstheporusacus/cusoftheinternalauditory meatusaccompaniedbythenervusintermedius,theves/bulocochlear nerveandthelabyrinthinevessels. Thelabyrinthinesegmentrunsfromthefundusoftheinternalacous/c meatustothegeniculateganglion,wherethenervemakesthefirstbend Thetympanicpartini/allycurvesaroundtheovalwindowniche,then liesjustanteriorandinferiortothelateralsemicircularcanalandbends againatthesecondgenutobecomethever/calormastoidpart. Themastoidpartisthelongestofthepetroussegmentsandrunsfrom thepyramidalprocesstothestylomastoidforamen. 55 THEEAR THEFACIALNERVE Themainbranchfromthegeniculateganglionisthegreaterpetrosal nerve,abranchofthenervusintermedius. Thegreaterpetrosalnervepassesanteriorly,receivesabranchfrom thetympanicplexusandtraversesahiatusontheanteriorsurfaceof thepetrouspartofthetemporalbone. Itentersthemiddlecranialfossa,itisjoinedbythedeeppetrosalnerve fromtheinternalcaro/dsympathe/cplexus,tobecomethenerveof thepterygoidcanal 56 THEEAR THEFACIALNERVE Thegreaterpetrosalnervecontainsparasympathe/cfibresdes/ned forthepterygopala/neganglion,andtastefibresfromthepalate. Thenervetostapediusarisesfromthefacialnerveinthefacialnerve canalbehindthepyramidaleminenceoftheposteriorwallofthe tympaniccavityandpassesforwardsthroughasmallcanaltoreachthe muscle. Thechordatympanileavesthefacialnerveabovethestylomastoid foramenandrunsantero-superiorlyinacanaltoenterthetympanic cavityviatheposteriorcanaliculus. 57 THEEAR THEFACIALNERVE Thechordatympanileavescrossesmedialtotheupperpartofthe handleofthemalleustotheanteriorwallofthetympaniccavity, whereitenterstheanteriorcanaliculus. Itexitstheskullatthepetrotympanicfissure.Thechordatympani containsparasympathe/cfibresthatsupplythesubmandibularand sublingualsalivaryglandsviathesubmandibularganglionandtaste fibresfromtheanteriortwo-thirdsofthetongue. 58 THEVESTIBULOCOCHLEARNERVECNVIII THEVESTIBULOCOCHLEARNERVE Theves/bulocochlearnervecarriesspecialafferentfibersforhearing (thecochlearcomponent)andbalance(theves/bularcomponent) Theves/bulocochlearnerveemergesfromthecerebellopon/ne angle,betweentheponsandmedulla Itcoursesthroughtheposteriorcranialfossaincloseassocia/onwith thefacialnerve,nervusintermediusandlabyrinthinevessels. 59 THEVESTIBULOCOCHLEARNERVECNVIII THEVESTIBULOCOCHLEARNERVE Itentersthepetroustemporalboneviatheporusacus/cusofthe internalacous/cmeatus,anddividesinto: • ananteriortrunk, • thecochlearnerve,and • aposteriortrunk,theves/bularnerve ThevesLbularnerveenlargestoformthevesLbularganglion,before dividingintosuperiorandinferiorparts,whichdistributetothethree semicircularductsandtheutricleandsaccule Thecochlearnerveentersthebaseofthecochleaandpassesupward throughthemodiolus. 60 THEVESTIBULOCOCHLEARNERVECNVIII THEVESTIBULOCOCHLEARNERVE Theganglioncellsofthecochlearnerveareinthespiralganglionat thebaseofthelaminaofmodiolusasitwindsaroundthemodiolus Branchesofthecochlearnervepassthroughthelaminaofmodiolus toinnervatethereceptorsinthespiralorgan. 61