ear & auditory pathway

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..