inner ear anatomy ppt. Dr Javed shah FRCS ,Bannu Medical College

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Anatomy of inner Ear:

Anatomy of inner Ear Inner Ear Lies in Petrous part of temporal bone. Inner Ear consist of two Parts 1/ Bony (Osseous ) Labyrinth. 2/ Membranous Labyrinth

Slide 2:

Embryology: Thickening of ectoderm. Pit and vesicle formation,sinks deep to mesenchyma. Pit and then vesicle, sinks to deep mesenchyma Embryology: Thickening of ectoderm.

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The vesicle forms Membranous Labyrinth The surrounding Mesenchyma forms the Bony Labyrinth, Hardest bone. Perilymphatic space

Slide 4:


Bony(osseous labyrinth):

Bony(osseous labyrinth) Vestibule: central area between lateral termination of IAM and tympanic cavity. Size: ASpirin tablet. Communicates anteriorly with scala vestibule And posteriorly with 5 openings of SCC>

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Medial wall of vestibule: 8th nerve Lateral wall, oval window and round window.

Slide 8:

Medial wall of vestibule. perforations for 8th nerve. The front half of medial wall has Saccule of membranous labyrinth the posterior half contains Utricle orifice of aqueduct of vestibule.

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The Semicircular Canals: Posterior end of bony Labyrinth. 3 SCC, Lateral, Posterior and Superior, 2/3 of a circle

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Each canal has 2 opening to vestibule one opening of each canal is dilated called Ampulary end Non ampulary ends of Posterior and superior canal make common opening. total 5 openings to vestibule


Cochlea Anterior part of bony labyrinth Hollow tube taking 2and3/4 turn round Modiolus. where the tube is applied to modiolus ,crest of bone like flange of screw projects to lumen dividing almost to 2 tube, Helicotrema

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Modiolus abuts on the cholera area of IAM Cochlear nerve enters in the centre and periphery. distance from base to apex is 5 mm. length of cochlear duct is 30 mm.

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Scala vestibule scala tympani

Membranous Labyrinth:

Membranous Labyrinth Otic vesicle. 2 out growths Anterior forms cholera duct(scala media)and endolymphatic duct and sac Posterior part forms sacule,utricle and 3 scc .

Slide 16:

Semicircular canals. superior and lateral have 3 openings, crus commune and 2 ampulary ends,lat scc have 2 openings to utricle . total 5 opening to utricle.

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Cochlear duct . starts at saccule by canalis reunion. Basilar membrane,attaches to spiral lamina aand lateral wall of bony cochlea.and divide the chclear duct to scala vestibule and tympani

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basilar membrane epithelium show modification ,organ of corti Scala media triangular on section

Slide 20:

Sensory areas in membranous ssc and cochlea. 1/ Crista ampullaris of ssc 2/Macula in utricle and saccule. 3/organ of corti

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Blood supply of internal Ear. internal auditory artery, branch of anterior cerbellar artery, cochlear and vestibular branches veins of same name drain to petrosal sinus

Slide 22:

Vestibular cochlear nerve.

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