ear & auditory pathway
TRANSCRIPT
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Ear & Auditory pathway
By:DR.KRUPA RAITHATHAR.K.UNIVERSITY,
Rajkot,Gujrat,India.
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Structure of EarO EXTERNAL EAR
o Auricleo External auditory meatus
O MIDDLE EARo Tympanic cavityo Tympanic membraneo Auditory ossicleso Muscleso Auditory tube
O INTERNAL EARo Cochlea o Compartments of cochleao Organ of corti
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External ear
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Auricle• Fibrocartilaginous
plate• Covered by connective
tissue & skin.• Fine hairs,sebaceous
gland & sweat glands.• Not movable in
humans because of rudimentary muscles.
• Forms orifice of External auditory meatus.
• Depression of auricle=concha.
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External auditory meatus
O2 parts:1.Outer: cartilaginous part2. Inner :bony part
1.Thick skin,stiff hair,sebaceous gland+cereminous gland+desquamated epithelial cells=earwax2. Only sebaceous glands,continuous with tympanic membrane
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Middle ear
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Tympanic cavity/tympanum
OSmall,narrow, laterally compressed chamber
OSituated within the temporal bone.
OSeparated from EOM by tympanic membrane
OContains auditory ossicles.
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Tympanic membraneOSemitransparentOPeriphery is fixed
to tympanic sulcus in surrounding bony ring by fibrocartilage.
O3 layers:• Cuticular layer• Fibrous layer• Inner mucus
layer/tympanic mucosa
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Auditory ossiclesO 3 bones:• Malleus/
hammer:Head,neck,handle• Incus/anvil
Body,long & short process
Tip-lenticular process• Stapes/stirrup
Smallest boneHead,neck,ant.cru
s,post.crus,footplate.
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MusclesOTensor tympani:o Keeps tympanic
membrane stretched & tensed.
o Supplied by mandibular division of trigeminal nerve.
OStapediusOReduces
movements of footplate against the fluid in cochlea.
OSupplied by facial nerve.
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Auditory tube/Eustachian tube
OFrom ant. Wall of middle ear to nasopharynx.
OUpper part:bony wallOLower part:
fibrocartilaginous plate
OConnects middle ear to nose so pressure on both the sides of tympanic membrane is equalised.
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Internal ear/labyrinth
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OMembranous structure in petrous part of temporal bone.
OConsists of sense organs of Hearing(COCHLEA) & Equilibrium(VESTIBULAR APPARATUS-semilunar canals & otolith organ).
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CochleaO2 Parts:OModiolus:central
conical spongy bone.
OBony canal/tube: winds around modiolus.
O2.5 circlesOEnd of
canal=capula.OCochlear nerve
pass through.
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Compartments of cochlea
O2 membranes:• Basilar
membrane/membraneous spiral lamina
• Vestibular membrane/reissner’s membrane
O3 compartments/scalae:• Scala vestibuli• Scala tympani• Scala media/cochlear duct
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OSection through axis of cochlea reveals the central bony pillar,modiolus and periodic or osseous canal.
OEnd of capula,hook shaped process= hamulus.
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Organ of cortiOReceptor organ
for hearing.ONeuroepithelial
structure in cochlea.
OLocated upon the lip of osseous spiral lamina & basila membrane.
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OMadeup of sensory elements,hair cells & other supporting cells.
OOther cells from periphery to center:o Border cellso Inner hair cellso Inner phalangeal
cellso Inner pillar cellso Outer pillar cellso Outer phalangeal
cellso Outer hair cells
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Auditory pathway
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Thank you..