Anatomy of ear

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componentsAuricleExternal acoustic canalTympanic membrane

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Auricle /pinna single piece of yellow elastic cartilage

covered with skinClosely adherant to perichondrium on lateral

surface than medialIncisura terminalis: no cartilage between

tragus n crus of helix .incision in this area for epidural approach use: as source of source of graft for reconstruction surgery of middle ear etc

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External acaustic /auditory canal24 cms along posterior wall upper wall directed upwards, backwards,

mediallyInner part: downwards, forwards ,mediallyFor allignment :pulled upwards, backwards,

medially

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(a)Cartilagenous part8mmhas 2 deficiencies:fissure of santorini; part

through which parotid or superior mastoid infection occur

Furuncles(staphylococcal infection) in outer 1/3 of canal due to hair follicles

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(b)Bony part16mm devoid of hair, ceruminous glands6mm lateral to tympanic membrane bony

meatus presents narrowing :”isthmus”Anteroinferior part of deep meatus beyond

isthmus presents recess-”ant recess”Anteeroinferior part of bony canal may

presents deficiency (foramen of huschke)

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Tympanic memb/ear drum9-10mm tall,8-9mm wide,.1mm thickDivided into 2 parts (a) pars tensaThick perifery ,form fibrocartlagenous ring

called ”annulus tympanicus”Central part tensed inwards at tip of malleus

‘UMBO’

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(b)Pars flacida /shrapnels membraneBetween notch of rivinus n anterior n

posterior malleal folds LAYERS OF TYMPANIC MEMBRANEOuter epIthelial layerInner mocosal layerMiddle fibrous layer

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Nerve supply of external earGreater auricular nerveLesser occipital nerveAuriculo temporal nerveAuricular branch of vagus EXTERNAL AUDITORY CANALFacial nerveAuriculo temporal nerveAuricular br of vagus nerve TYMPANIC MEMBRANEAuriculo temporal nerveAuri br of vagus nerveJacobsons nerve

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MIDDLE EAR

Middle ear cleft: eustachian tube,aditus,antrum,mastoid air cells

Divided into: mesotympanium,epitympanum,hypotympanum

Linked to 6 sided box

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roofFormed by thin plate of bone : tegmen

tympani,forms roof of aditus n antrum FLOORThin plate of bone seperates tympanic

cavity from jug bulb ANTERIOR WALLThin plate of bone seperates cavity from

internal carotid art2 openings: eustachian tube, tensor

tympani musclepgmedicalworld.com

Posterior wallClose to mastoid air cellsPresents bony progectn”pyramid”,tendon

of stapedius is attachad to neck of stapesSurgically important as direct access can

be made through middle earFacial recess/ posteauor sinus: depression

in post wall lateral to pyramid

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Medial wallFormed by labyrinthPresents bulge” promontary”Oval window fixed to foot plateRound window covered by sec tympanic

membraneOver oval window is canal for facial n Just anterior to oval window, hook like

progection” pocessus cochleariformis”

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Lateral wallFormed by tympanic membrane n bony

outer attic wall ”scutum”

OSSICLES OF MIDDLE EAR

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Malleus:head,neck,handle,lateral and anterior

processIncus:body,short and long processStapes: head, neck, anterioe and posterior

crura, foot plate

INTRA TYMPANIC MUSCLES Tensor tympani stapedius

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THE INTERNAL EAR

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Bony and membranous labyrinth filled with endolymph and perylymph respectively

Bony labyrinth3 parts:vestibule,semicircular canals,cochleaVestibule:the central canal of labrynthLatwral wall:oval windowMedial wall: 2 recess: spherical and ellipticalBelow opening of elliptical recess is opening

of aqueous duct through which passes endolymphatic duct

Posterior part of vestibule:5 openings of semisircular canals

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Semicircular canals3 in number: lateral,posterior,superior at right

angles to each otherHas amputated n nonamputated end,Nonamputated ends of posterior n superior

canals unite to form channel ”crus commune” conchaeCoiled tube making2.5-2.75 turns round

central pyranid ”modiolus”“osseous spiral lamina”:around modiolus

winding spirally like thread of screw3 componants: scala vestibuli Scala tympani Scala media

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THANK YOU

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