ear & auditory pathway
TRANSCRIPT
Ear & Auditory pathway
By:DR.KRUPA RAITHATHAR.K.UNIVERSITY,
Rajkot,Gujrat,India.
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
External ear
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.
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
Middle ear
Tympanic cavity/tympanum
OSmall,narrow, laterally compressed chamber
OSituated within the temporal bone.
OSeparated from EOM by tympanic membrane
OContains auditory ossicles.
Tympanic membraneOSemitransparentOPeriphery is fixed
to tympanic sulcus in surrounding bony ring by fibrocartilage.
O3 layers:• Cuticular layer• Fibrous layer• Inner mucus
layer/tympanic mucosa
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.
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.
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.
Internal ear/labyrinth
OMembranous structure in petrous part of temporal bone.
OConsists of sense organs of Hearing(COCHLEA) & Equilibrium(VESTIBULAR APPARATUS-semilunar canals & otolith organ).
CochleaO2 Parts:OModiolus:central
conical spongy bone.
OBony canal/tube: winds around modiolus.
O2.5 circlesOEnd of
canal=capula.OCochlear nerve
pass through.
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
OSection through axis of cochlea reveals the central bony pillar,modiolus and periodic or osseous canal.
OEnd of capula,hook shaped process= hamulus.
Organ of cortiOReceptor organ
for hearing.ONeuroepithelial
structure in cochlea.
OLocated upon the lip of osseous spiral lamina & basila membrane.
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
Auditory pathway
Thank you..