Download THE PTERYGOPALATINE FOSSA MAXILLARY NERVE EAR

THE
PTERYGOPALATINEFOSSA
MAXILLARYNERVE
EAR
VESTIBULOCOCHLEARNERVE
CNVIII
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THEPTERYGOPALATINEFOSSA
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THEPTERYGOPALATINEFOSSA
THEPTERYGOPALATINEFOSSA
Thepterygopala/nefossaliesbetween:
•  thepterygoidprocessofthesphenoidposteriorlyand
•  theroundedposterioraspectofthemaxillaanteriorly.
Thepterygopala/nefossaisanirregularlyshapedspaceposteriorto
themaxillaandinferioranddeeptothezygoma/carch.
Becauseofitsstrategicloca/on,thepterygopala/nefossaisamajor
siteofdistribu/onforthemaxillarynerveV2andfortheterminal
partofthemaxillaryartery.
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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.
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THEPTERYGOPALATINEFOSSA
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THEPTERYGOPALATINEFOSSA
THEPTERYGOPALATINEFOSSA-OPENNINGS
PTERYGOMAXILLARYFISSURETHEINFRATEMPORALFOSSA SPHENOPALATINEFORAMEN THENASALCAVITY
INFERIORORBITALFISSURE
THEORBIT
PALATINECANAL THEHARDANDTHESOFTPALATE
FORAMENROTUNDUMTHEMIDDLECRANIALFOSSA PTERYGOIDCANAL THEFORAMENLACERUM
PHARYNGEALCANAL THENASOPHARYNX
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THEPTERYGOPALATINEFOSSA
THEPTERYGOPALATINEFOSSA
ThepterygopalaLnefossacontains:
•  themaxillarynerveV2
•  thepterygopalaLneganglion
•  thenerveofthepterygoidcanal,and
•  thethirdorpterygopalaLnepartofthemaxillaryarteryandits
branches
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THEPTERYGOPALATINEFOSSA
THEPTERYGOPALATINEFOSSA
LymphaLcdrainageofthetemporal,infratemporal,and
pterygopala/nefossaeistoregionallymphnodes-thesuperficial
nodesatthejunc/onoftheheadandneckandthesuperiordeep
cervicalnodesalongthecaro/dsheath.
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THEMAXILLARYNERVE
THEMAXILLARYNERVE
Themainnervesassociatedwiththetemporal,infratemporal,and
pterygopala/nefossaearebranchesofthemaxillaryV2and
mandibularV3nerves,whicharedivisionsofthetrigeminalnerveCNV
ThemaxillarynerveV2leavesthemiddlecranialfossathroughthe
foramenrotundumandentersthepterygopalaLnefossa.
Itisasensorynervewithnomotorcomponent,anditsbranches
providesensa/ontothemidsec/onoftheface:
•  lowerpartoftheorbit,
•  nose,
•  upperpartofthemouth,and
•  cheek
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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.
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THEMAXILLARYNERVE
THEMAXILLARYNERVE
Thisganglionreceivesautonomicinnerva/onfromthenerveofthe
pterygoidcanal,whichisacombina/onoftwonerves:
•  theparasympatheLcroot(abranchofthefacialnerve[VII])
•  thesympatheLcroot(whichoriginatesfromthesuperiorcervical
ganglion)
NervesfromthepterygopalaLneganglioncarryparasympathe/c
andsympathe/cfibersandsensorynervesfromthemaxillarynerve
V2tosupply:
•  thelacrimalglandand
•  glandsinthenasaland
•  upperoropharyngealregions.
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THEMAXILLARYNERVE
THEMAXILLARYNERVE
ThemaxillarynerveV2leavesthepterygopala/nefossathroughthe
inferiororbitalfissure.
Fromthispointitisreferredtoastheinfra-orbitalnerve
Itenterstheorbitandpassesanteriorlywithintheinfra-orbitalgroove
andthenwithintheinfra-orbitalcanalun/litemergesontotheface
approximately1cminferiortotheinferiororbitalrim
Theinfra-orbitalnerveprovidessensa/onto:
•  theskinoftheupperlip,
•  lowereyelid,
•  cheek,and
•  lateralpartofthenose.
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THEPTERYGOPALATINEGANGLION
THEPTERYGOPALATINEGANGLION
Isthelargestofthefourparasympathe/cgangliaintheheadandis
formedbythecellbodiesofthepostganglionicneuronsassociated
withpreganglionicparasympathe/cfibersofthefacialnerve[VII]
carriedbythegreaterpetrosalnerveandthenerveofthepterygoid
canal.
Themaxillarynervegivesoffthetwoganglionicbranchestothe
pterygopala/neganglion(sensoryrootsofthepterygopala/ne
ganglion)thatsuspendtheparasympathe/cpterygopala/neganglion
inthesuperiorpartofthepterygopala/nefossa
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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
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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
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THEPTERYGOPALATINEGANGLION
THEPTERYGOPALATINEGANGLION
Themajorityofthe‘branches’oftheganglionareprimarilysensory
branchesofthemaxillarynerve.Thustheypassthroughtheganglion
withoutsynapsingandenterthemaxillarynervethroughitsganglionic
branches;theyconveysomeparasympathe/cfibrestothepala/ne,
pharyngealandnasalmucousglands.
Generalsensoryfibresdes/nedfordistribu/onviaorbital,
nasopala/ne,superioralveolar,pala/neandpharyngealbranchesof
themaxillarydivisionofthetrigeminalnerverunthroughtheganglion
withoutsynapsing.
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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.
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THEEXTERNALEAR
THEEAR
Theauricleissupportedbycar/lageandiscoveredbyskin.The
externalauditorymeatusisneartheanteriormarginoftheauricle.
Theauriculotemporalnerve,abranchofCNV3,suppliestheskinof
theauricleanteriortotheexternalacous/cmeatus
Minorcontribu/onsofembryologicalsignificancearemadetotheskin
oftheconchaanditseminenceby:
•  thevagusCNXand
•  thefacialnervesCNVII.
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THEEXTERNALEAR
THEEAR
Thelympha/cdrainageoftheauricleisasfollows:
•  thelateralsurfaceofthesuperiorhalfoftheauricledrainstothe
superficialparo/dlymphnodes
•  thecranialsurfaceofthesuperiorhalfoftheauricledrainstothe
mastoidlymphnodesanddeepcervicallymphnodes;
•  theremainderoftheauricle,includingthelobule,drainsintothe
superficialcervicallymphnodes.
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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.
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THEEXTERNALEAR
THEEAR
THETYMPANICMEMBRANE
•  Theexternalsurfaceofthetympanicmembraneissuppliedmainly
bytheauriculotemporalnerve,abranchofCNV3
•  Someinnerva/onissuppliedbyasmallauricularbranchofthe
vagus(CNX).
•  Theinternalsurfaceofthetympanicmembraneissuppliedbythe
glossopharyngealnerve(CNIX).
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THEMIDDLEEAR
THEMIDDLEEAR
Thecontentsofthemiddleeararethe:
•  auditoryossicles(malleus,incus,andstapes)
•  stapediusandtensortympanimuscles
•  chordatympaninerve,abranchofCNVII
•  tympanicplexusofnerves
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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.
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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.
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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
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THETYMPANICCAVITY
THEMIDDLEEAR
INNERVATION
Thetympaniccavitycontainsthetympanicplexusandthefacialnerve.
Branchesfromtheplexusandthefacialnervesupplystructureswithin
thetympaniccavitybutalsoleavethecavitytosupplystructureson
theface.
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THEPHARYNGOTYMPANICTUBE
THEMIDDLEEAR
Thepharyngotympanictubeconnectsthetympaniccavity(anterior
wall)tothenasopharynx,whereitopensposteriortotheinferiornasal
meatus
Itallowstheairpressureoneithersideofthetympanicmembraneto
equalize.
isopenedbytheexpandinggirthofthebellyofthelevatorvelipala/ni
asitcontractslongitudinally,pushingagainstonewallwhilethetensor
velipala/nipullsontheother
Thenervesofthepharyngotympanictubearisefromthetympanic
plexuswhichisformedbyfibersoftheglossopharyngealnerve(CNIX).
Anteriorly,thetubealsoreceivesfibersfromthepterygopala/ne
ganglion.
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THEAUDITORYOSSICLES
THEMIDDLEEAR
Thebonesofthemiddleearconsistof:
•  themalleus,
•  incus,and
•  stapes
Theseossiclesarethefirstbonestobefullyossifiedduring
developmentandareessen/allymatureatbirth,
unlikeotherbones,theylackasurroundinglayerofosteogenic
periosteum
Theyformanosseouschainofthreemobileossiclesacrossthemiddle
earfrom:
•  thetympanicmembrane
•  totheovalwindowoftheinternalear
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THEAUDITORYOSSICLES
THEMIDDLEEAR
transferssoundwavesacrossthetympaniccavityfromthetympanic
membranetothefenestraves/buliofthebonylabyrinth.
Themalleusisakachedtothetympanicmembrane,andthebase
(footplate)ofthestapesisakachedtotherimofthefenestraves/buli.
Theincusissuspendedbetweenthemandar/culateswithbothbones.
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THEAUDITORYOSSICLES-MALLEUS
THEMIDDLEEAR
MALLEUS-iden/fiablepartsinclude:
•  theheadofmalleus
•  neckofmalleus
•  anteriorandlateralprocesses
•  handleofmalleus
MALLEUS
Theheadofthemalleusar/culateswiththeincus;thetendonofthe
tensortympaniinsertsintoitshandleneartheneck.
MALLEUS
Themalleusfunc/onsasalever,withthelongerofitstwoprocesses
anditshandleakachedtothetympanicmembrane.
MALLEUS
Thechordatympaninervecrossesthemedialsurfaceoftheneckofthe
malleus.
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THEAUDITORYOSSICLES-INCUS
THEMIDDLEEAR
INCUS
islocatedbetweenthemalleusandthestapes.
Itconsistsof:
•  thebodyofincusand
•  thelongandshortlimbs
INCUS
Theenlargedbodyofincusar/culateswiththeheadofmalleusandis
intheepitympanicrecess.
INCUS
Thelonglimbextendsdownwardfromthebody,parallelingthehandle
ofthemalleus,andendsbybendingmediallytoar/culatewiththe
stapes.
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THEAUDITORYOSSICLES-STAPES
THEMIDDLEEAR
STAPES
Thestapesisthemostmedialboneintheosseouschainandis
akachedtotheovalwindow.
consistsof:
•  theheadofstapes
•  anteriorandposteriorlimbs
•  thebaseofstapes
STAPES
Theheadofstapesisdirectedlaterallyandar/culateswiththelong
processoftheincus.
STAPES
Thebaseofstapesfitsintotheovalwindowonthelabyrinthinewallof
themiddleear.
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THEMIDDLEEAR
THEMUSCLESASSOCIATEDWITHTHEOSSICLES
Twomusclesareassociatedwiththebonyossiclesofthemiddleear:
•  thetensortympani
•  thestapedius
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THEMIDDLEEAR
THEMUSCLESASSOCIATEDWITHTHEOSSICLES
TENSORTYMPANI
ORIGIN:car/laginouspartof
pharyngotympanictube,greater
wingofsphenoid,itsownbony
canal
INSERTION:upperpartofhandle
ofmalleus
TENSORTYMPANI
INNERVATION:branchfrommandibularnerveV3
TENSORTYMPANI
FUNCTION:contrac/onpullshandleofmalleusmedially,tensing
tympanicmembrane
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THEMIDDLEEAR
THEMUSCLESASSOCIATEDWITHTHEOSSICLES
STAPEDIUS
ORIGIN:akachedtoinsideof
pyramidaleminence
INSERTION:neckofstapes
STAPEDIUS
INNERVATION:branchoffacialnerveVII
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THEMIDDLEEAR
THEINNERVATIONOFTHEMIDDLEEAR
Thetympanicplexusinnervatesthemucousmembraneliningthewalls
andcontentsofthemiddleear,whichincludesthemastoidareaand
thepharyngotympanictube.
Thetympanicplexusisformedby:
•  thetympanicnerve,abranchoftheglossopharyngealnerve[IX],and
•  frombranchesoftheinternalcaroLdplexus.
Branchesfromthetympanicplexussupplythemucousmembranesof
themiddleear,includingthepharyngotympanictubeandthemastoid
area.
Thetympanicplexusalsogivesoffamajorbranch(thelesserpetrosal
nerve),whichsuppliespreganglionicparasympathe/cfibers
totheo/cganglion
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THEINTERNALEAR
THEINTERNALEAR
Theinternalearconsistsof:
•  aseriesofbonycavi/es-thebonylabyrinthand
•  membranousductsandsacs-themembranouslabyrinthwithin
thesecavi/es.
Allthesestructuresareinthepetrouspartofthetemporalbone
betweenthemiddleearlaterallyandtheinternalacous/cmeatus
medially
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THEINTERNALEAR
THEBONYLABYRINTH
Thebonylabyrinthconsistsof:
•  thevesLbule
•  threesemicircularcanals
•  thecochlea
Thebonycavi/esarelinedwithperiosteumandcontainaclearfluid
theperilymph
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THEINTERNALEAR
THEBONYLABYRINTH
Thebonylabyrinthisthefluid-filledspace,whichissurroundedbythe
o/ccapsule,andisrepresentedbyacastoftheo/ccapsulea^er
removalofthesurroundingbone.
ThevesLbularaqueductleavestheves/bule,andpassesthroughthe
temporalbonetoopenontheposteriorsurfaceofthepetrouspartof
thetemporalbone.
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THEINTERNALEAR
THECOCHLEA
Thecochleaistheshell-shapedpartofthebonylabyrinththatcontains
thecochlearduct,thepartoftheinternalearconcernedwithhearing.
Thecochleaisabonystructurethattwistsonitselftwoandone-halfto
twoandthree-quarter/mesaroundacentralcolumnofbone,
themodiolus
Themodioluscontainscanalsforbloodvesselsandfordistribu/onof
thebranchesofthecochlearnerve.
Thisarrangementproducesacone-shapedstructurewithabaseof
cochleathatfacesposteromediallyandanapexthatfaces
anterolaterally
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THEINTERNALEAR
THECOCHLEA
Thisposi/onsthewidebaseofthemodiolusneartheinternalacous/c
meatus,whereitisenteredbybranchesofthecochlearpartofthe
ves/bulocochlearnerve[VIII].
Extendinglaterallythroughoutthelengthofthemodiolusisathin
laminaofbone-thelaminaofmodiolusorspirallamina
Circlingaroundthemodiolus,andheldinacentralposi/onbyits
akachmenttothelaminaofmodiolus,isthecochlearduct,whichisa
componentofthemembranouslabyrinth.
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THEINTERNALEAR
THECOCHLEA
Akachedperipherallytotheouterwallofthecochlea,thecochlear
ductcreatestwocanals-thescalavesLbuliandthescalatympani
ThescalavesLbuliandthescalatympaniarecon/nuousattheapex
throughanarrowslitthehelicotrema
ThescalavesLbuliiscon/nuouswiththeves/bule.
Thescalatympaniisseparatedfromthemiddleearbythesecondary
tympanicmembranecoveringtheroundwindow
Neartheroundwindowisasmallchannelthecochlearcanaliculus.
Itprovidesaconnec/onbetweentheperilymph-containingcochlea
andthesubarachnoidspace.
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THEINTERNALEAR
THEMEMBRANOUSLABYRINTH
Themembranouslabyrinthisacon/nuoussystemofductsandsacs
withinthebonylabyrinth
Itisfilledwithendolymphandseparatedfromtheperiosteumthat
coversthewallsofthebonylabyrinthbyperilymph
Themembranouslabyrinth,composedoftwodivisions:
•  theves/bularlabyrinth
•  thecochlearlabyrinth
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THEINTERNALEAR
THEMEMBRANOUSLABYRINTH
Consis/ngoftwosacs:
•  theutricle
•  thesaccule
andfourducts:
•  thethreesemicircularducts
•  thecochlearduct
Theves/bularlabyrinthandthecochlearlabyrinth,consistsofmore
partsthandoesthebonylabyrinth:
•  vesLbularlabyrinth:utricleandsaccule,twosmallcommunica/ng
sacsintheves/buleofthebonylabyrinth.
•  threesemicircularductsinthesemicircularcanals.
•  cochlearlabyrinth:cochlearductinthecochlea.
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THEINTERNALEAR
THEMEMBRANOUSLABYRINTH
Thesemicircularductsopenintotheutriclethroughfiveopenings,
reflec/veofthewaythesurroundingsemicircularcanalsopen
intotheves/bule.
Theutriclecommunicateswiththesacculethroughthe
utriculosaccularduct,fromwhichtheendolympha/cductarises
Thesacculeiscon/nuouswiththecochlearductthroughtheductus
reuniens,auni/ngduct.
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THEINTERNALEAR
THEMEMBRANOUSLABYRINTH
ThereceptorsforauditoryandvesLbularfuncLonarelocatedwithin
themembranouslabyrinth
Theutricleandsacculehavespecializedareasofsensoryepithelium
calledmaculae.
Thehaircellsinthemaculaeareinnervatedbyfibersoftheves/bular
divisionoftheves/bulocochlearnerve.
Inthemaculae,theweightoftheotoconialcrystalscreatesagravita/onal
pullontheotoconialmembraneandthusonthestereociliarybundlesof
thesensorycellsthatareinsertedintoitsbase.Becauseofthis,theyare
abletodetectthesta/corienta/onoftheheadwithrespecttogravity.
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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