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Question : Briefly describethe structureof earwith the help of a suitablediagram.

Answer»

Solution :(1)The ear iscomposedof the outer ear, middle ear andinternal ear.
(2) The external earconsistsof the pinnaand externalauditorymeatus (canal). The pinnacollectssoundwaves comingfrom theenvironment.The externalauditory canal isthe circulartube leading insideup to the eardrum. (tympanic membrane).
(3) The ear drum isformedof connective tissueshavingouter skin cover andinner mucus membrane.
(4) Themiddle ear consists of chain of three ossiclescalled malleus,incus andstapes.The malleusis attached totympanicmembraneand the stapesis connectedto the oval window of theinternal ear.They helpin the transmission of soundwaves fromexternalauditorycanalto internalear.
(5)Connectingmiddle earwith the pharynx is aneustachiantube which helpsin equalizingthe air pressureon eitherside of thetympanicmembrane.
(6) The internal ear isfluidfilledstructurecalled bonylabyrinthand the membranouslabyrinth.
(7) The membranes consist of coiledcochlea,the reissner'smembraneand basilarmembranes.Thesemembranesdivide thesurroundingperilymphfilled bonylabyrinth into an upperscalavestibule and a lowerscalatympani.
(8)The space within COCHLEA which is knwon as scala media is filled with endolymph. The scala vestibule ends at the oval window at the base of cochlea.
(9) Thescalatympani terminates at the roundwindow whichopensto themiddle ear.The organ of thecorti is locatedonthe brasillarmembrane.It containsthe haircells whichact asauditory receptors.A thinelasticmembraneprojects above therows of thehairscellscalled tectorialmembrane.
(10) Abovethe cochlea. the internalear alsocontainsvestibularapparatus.It consistsof threesemicircularcanals whcihare in PERILYMPH and the OTOLITH organsformed of thesacculus andutriculus.
(11) Thebases of canalsare swollenand are calledampullae.
Whichcontain a PROJECTING ridgeknow as crista ampullariswhichcontainhair calls.
(12)The sacculus and utriculus also haveprojectingridgecalledmacula. The cristaand maculaare the specificreceptorsof vestibular apparatus . They are responsiblefor maintenance of bodyposture and the balance.
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