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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
pgmedicalworld.com