Internal ear Labyrinth Internal ear Petrous temporal BONY

Internal ear Labyrinth

Internal ear Petrous temporal

BONY LABYRINTH Perilymph MEMBRANOUS LABYRINTH Endolymph

Semicircular canals BONY LABYRINTH Superior/anterior Vestibule Posterior Lateral Cochlear canal

Vestibule Modiolus

Semi Circular Canal VESTIBULE VERTICAL: 5 mm SPHERICAL RECESS A/P: 5 mm WIDTH: 3 mm COCHLEAR RECESS FENESTRA VESTIBULI

VESTIBULAR CREST ELLIPTICAL RECESS SPHERICAL RECESS COCHLEAR RECESS

Semicircular canals Posterior Common crus End ANTERIOR OF ONE SIDE IS PARALLEL TO POSTERIOR OF THE OTHER SIDE Superior/ anterior Ampulla Upper End Posterior Lateral LATERAL CANAL OF BOTH THE SIDES LIE IN SAME PLANE

MEMBRANOUS LABYRINTH Cochlear duct SEMICIRCULA R DUCTS Cochlear nerve Anterior Lateral Posterior Vestibulocochlear nerve Vestibular nerve

Round window

COCHLEAR DUCT Modiolus Spiral lamina

Osseus spiral lamina Scala vestibuli Nerve fibres Reissner’s membrane / VM Cochlear duct Spiral ligament Tectorial membrane Cochlear modiolus Spiral organ of corti Spiral ganglion Basilar membrane ORGAN OF CORTI outer hair cell Osseus cochlea Cochlear nerve Scala tympani SUPPORTING CELLS Inner hair cell

UTRICLE SEMICIRCULAR COCHLEAR DUCTS A P SACUULE

SACCULE & UTRICLE ENDOLYMPHATIC SAC DUCTUS REUNIENS

INTERAL EAR COCHLEA ENDOLYMPHATIC DUCT & SAC AQUEDUCT OF VESTIBULE

SEMICIRCULAR CANALS VASTIBULAR MEMBRANOUS AMPULLA (ANTERIOR SEMICIRCULAR CANAL) GANGLION MEMBRANOUS AMPULLA (LATERAL SEMICIRCULAR CANAL) VESTIBULOCOCHLEAR NERVE CRUS COMMUNE LSCC VESTIBULAR NERVE MEMBRANOUS POSTERIOR AMPULLA SEMICIRCULAR P CANAL

VIII NERVE MACULA: STATIC BALANCE

VIII NERVE CRISTA: KINETIC BALANCE

Arterial supply Labyrithine artery Stylomastoid artery

Venous drainage Labyrithine vein – Superior petrosal Transverse sinus other veins drain: Into superior petrosal inferior petrosal IJV

Applied Anatomy Meniere’s disease • Due to distention of endolymph and degenerative changes in the organ of corti. • Patient complains of persistent attacks of nausea, vomiting, tinnitus & progressive deafness.

Mechanism of hearing

Tympanic membrane Ear ossicles Cochlear nerve External acoustic meatus Cochlear canal

Rinne’s test: Patient finds vibrating tuning fork louder when placed on mastoid process than when placed in front of affected ear B. C > A. C

Weber’s test: Bone conduction is better on the side of diseased middle ear when the vibrating tuning fork is placed on the centre of forehead B. C>A. C