Chapter 2 Vestibulocochlear OrganThe vestibulocochlear organ (Fig. IV-2-1) istemalearTheextermalandmiddleearsarethesoundcomposed of the auditory apparatus and vestibularolltingdtramingaparahialapparatus.Both organs buried in the temporal boneissuchanorganthatcanreceivethestimuliofbothare closely associated anatomically. It consists ofsound waves and changes of the position and move.three parts: theexternal ear, the middleear and the in-ment of the head.AuricleBony semicircular canalsVestibuleCochleaVestibulocochlearnFacialnTensortympaniBonypartofextemalacousticmeatusIntermal carotidaCartilaginous partofextermalacousticmeatusAuditory tubeCartilage ofauditory tubePharynxIntermal jugular v.TympanicmemFig. IV-2-1 The vestibulocochlear organexternal ear.It consists ofa single elastic cartilageSection1 Externalcovered with thin skin contains hairs, sweat glandsand sebaceous glands (Fig. IV-2-1, 2).The auricularEarlobule (earlobe)liesbelow theauricle,and consistsThe external ear consists ofthe auricle,externaloffibrous,adiposetissues and blood vessels.acousticmeatus andtympanicmembraneThe anterolateralsurfaceoftheauricleis iregularconcave, but its posteromedial surface presents con-vexThextenalacousticpore,rests inthefossaoI.Auriclethe anterolateral surface ofthe auricle,and leadstotheexternal acoustic meatus.The auricle or pinna is the shell like part of the·266扫描全能王创建
Chapter2 Vestibulocochlear Organ · 267 .HelixTriangular fossaCrura of antihelixCymba of auricular conchaCrus of helixAntihelixCavity of auricularconchaTragusAntitragusIntertragicAuricular lobuleFig, IV-2-2 The auriclesmeatus.II.External Acoustic Me-III .Tympanic MembraneatusThe tympanic membrane or eardrum is thin, semi-The external acoustic meatus or external auditorytransparent,and almostoval.It separates thetympan-canal extends from the external acoustic pore to theic cavity from the external acoustic meatus (Fig.IV-2-tympanicmembrane(Fig.IV-2-1).Itis approximate-1,3).Itis placedobliquelyforming an angle of45ly2.5cminlengthandhastwo structurallydifferentto55 degrees with the floor of the meatus, so that itsparts, the outer one third cartilaginous part and thelateral surfacefacesbothforward anddownward.inner two thirds osseous part.It is narrowed at theThe tympanic membrane is a connective tissuejunction of its osseous and cartilaginous parts.Be-membrane and composed of three layers:an outercause oftheobliquity of tympanic membrane,thecuticular layer, an intermediate fibrous layer and anwalls are not of the same length.Itforms an S-shapedinner mucous layer.The cuticular layer is continuouscurve,dircted atfirst medially,anteriorly and slighwith the skin of the external acoustic meatus andlyup,then posteromedially and up,and lastly againhairless.The fibrous layer is covered on its outer cu-anteromedially and slightly down.The best view ofticular layer and on its internal surface by the mucousthe tympanic membrane is obtained if the auricle ismembrane of thetympanic cavity.It has an externalgently drawn upward and backward. The examinerlayer of radiating fibres diverging from thehandleofshould remember that the external meatus of a childthe malleus and a deep layer of circular fibres.Theis very short.mucous layer is lined with the mucous membrane ofThe external acoustic meatus is lined by a layerthetympanic cavity.fthinskinwhichalsocoverstheoutersurfaceoftheIts thickened margin of the membrane,thefibro-tympanicmembraneBeneaththesknliethewaxsecartilaginous ring,is inserted into thetympanic sulcuscretingerumnousglanwhhscretinghuat the medial end of the external acoustic meatus. Itmarwahkinoauithnandihastwo folds,the anteriorandposteriormalleolarsuutanustsuisscarcbutrcsenoryerfolds intheupperendofthetympanicmembrane,andthey are prolonged to the lateral process of the malle-boy pars omau,oreurifmmus.Above these twofolds,the small part of the mem-ondiio,thaietfsexrme pin扫描全能王创建
·268.PARTIVSENSORYORGANSthat isthetense panhefacidpartfthympanicbraneislax and thin,socalledthefaccid part,whilemembrane is devoid ofthefibrous layer.the remainder of the membrane is tightly stretched,Body of incusHeadofmalleusPosteriormalleolarfoldFlaccidpartMalleolarprominenceAnteriormalleolarfoldMalleolar strigFibrocartiliaginous ringUmbooftympanicmembraneTensepatConeof lightFig.IV-2-3 The tympanic membraneIn life the tympanic membrane is pearlygray.Thewall of the inner ear. It is a rather large cavity in thehandle of the malleus is firmly attached to the innertemporal bone.It is the main part of themiddle earsurface of the tympanic membrane as far as its center,its capacity is about 1-2 cm.There are auditory ossi-and its lower end lies opposite the point ofmaximumcles,ligaments,muscles,vessels and nerves inside theindrawingof themembrane,theumbo,formed bythetympanic cavity.The tympanic cavity is connectedtraction of the lower end of the handle of malleus.anteriorly with the nasopharynx by the auditory tube,Remember that the appearance of the malleus is seenand posteriorly with the mastoid cellsby the mastoidthrough the membrane and that the membrane is con-antrum.cave when viewed from this aspect.This concavityproduces a bright area, the cone of light, can be seenWalls of the tympanic cavityanteroinferiortotheumbo.Section 2 Middle EarThe tympanic cavity is shaped like a narrow, sixsided box (Fig. IV-2-1, 4, 5). It possesses six walls:The middle ear (Fig.IV-2-1) lies between the exter-1) Roof or tegmental wall is a thin plate ofnal ear and internal ear,and it includes:the tympaniccompact bone, called the tegmen tympani whichcavity,the auditory tube,the mastoid antrum and theseparates the middle cranial fossa from the tympanicmastoid air cells.cavity. In youth, the unossifed suture ofthe superiorwall may allow the infection to spread from the tymI.Tympanic Cavitypanic cavity intothe cranial cavity directly and foman intracranial abscess.In adults, veins from the tympanic cavity traverse this suture to the superior sinusThe tympanic cavity is an irregular air filledand may alsotransmit infection tothese structures.spacebetween thetympanic membrane and the lateral扫描全能王创建
Chapter2VestibulocochlearOrgan ·269.IncusEntranceofmastoidantrum.Mastoid antrurmTegmentympanMastoidcellsMalleusStapeTympanicmemtStapedius.TensortympaniMastoidcellsAuditory tubeFacialnTubeof internaljugularaugularfosssFig.IV-2-4Thelateral walloftympanic cavityProminence of lateral semicircular ductMastoidantrumProminence offacial canalFenestravestibuliAuditory tubeMastoidcellsInternal carotidaPyramidaleminencPromontoryFenestracochleaeInternal jugular aIntemal jugular v.Facial nStyloid processMastoidprocessFig. IV-2-5 The medial wall of tympanic cavitywall aretwoparallel canals extendingtothetympanic2) Floor or jugular wall is narrower and thick-er than the tegmental wall. It separates the tympaniccavity.The upper and smaller is the smaller semicanalcavity from the jugular fossa. The bone of this wallfor tensor tympani; the lower and larger is a largersemicanal for auditory tube, the bony part of the audi-may be patchily deficient, so the tympanic cavitytory tube.is separated only from the jugular vein by mucous4)Posterior ormastoid wall is absent superi-membrane and fibrous tissue. This may cause theorly where the aditusto the mastoid antrum leaves thebeginning part of the jugular vein toproject intotheepitympanic recess.The pyramidal eminence is justtympanic cavity.below the opening of mastoid antrum and behind the3) Anterior or carotid wall is close to the in-fenestra vestibuli. It contains the stapedius.ternal carotid artery.Opening aboveon the anterior扫描全能王创建
·270·PARTIVSENSORYORGANSparalysis.5) Medial or labyrinthine wall is also the lat-6) Lateral or membranous wall consists al.eral boundaryof theinnerear.Aroundedelevationmost entirely of the tympanic membrane. Superiorlyonthemiddleofthiswall isnamedthepromontoryit isformed by the lateral wallof theepitympanicformed by the large first turn of the cochlea.The me-recess.Thehandleofthemalleus is incorporated indial wall has two small windows.Thefenestra ves-thetympanic membraneand its head extends intothetibuli or oval window is a reniform opening postero-epitympanic recess.superiorto thepromontory,and filled bythebaseofthe stapes and annular ligament. The fenestra cochleaAuditory ossiclesorround window lies posteroinferiortothetympanicpromontory,inferior to thefenestra vestibule,and isclosedbythe secondarytympanicmembraneinvivo.The three auditory ossicles, the malleus, incusInthe epitympanicrecess,abovethefenestravesti-and stapes,form ajointed arch between thetympanicbule,is an ill-defined,horizontal ridge produced bymembrane and the fenestra vestibule.the bone covering the canal for the facial nerve.TheLaterally,the handleofmalleus is attached to theprominence of facial canal is extends back and downtympanic membrane,andmedially,the base of thto the posterior wall of thetympanic cavity.Understapes is fixed to the margins of the fenestra vestibuli,inflammatoryconditionofthetympaniccavity,thefa-while the intermediate incus lies between the malleuscial canal may be involved, which may lead to facialand the stapes (Fig.IV-2-6).IncufeoEpitympanic recessBody of incusMalleusShort crusHeadofmalleutapesLongcrusHead of stapesExtemalacousticmeatuPosteriorcrusTympaniccavity ManubriumofTympanicmembr-BaseofstapesmalleusAnteranFig.IV-2-6The auditory ossiclesThe chain of ossicles transfers sound waves fromthe stapedius contract simultaneously. While the ten-the handle of themalleus to the incus and stapes,sortympani contracts, it pulls thehandle of the malle-transmitting the vibration to the inner ear.us medially,tenses the tympanic membrane,and thusreduces the amplitude of vibration.On the stapedius3. Muscles of the tympanic cavitycontraction, it pulls the neck ofthe stapes posteriorly,tilts the base in the fenestra vestibule tightening theThere are two muscles, the tensor tympani andannular ligament and reducing the pressure of soundstapedius, in each side of the tympanic cavity.Thewavefor the inner ear.tensor tympani arises from the semicanal for tensortympani and ends the handle of malleus. The stape-II.Auditory Tubedius arises from the pyramidal eminence of posteriorwall of the tympanic cavity and is inserted into theThe auditory tube, also named eustachian tube,neckofthestapes.Commonly,thetensortympaniand扫描全能王创建