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Prepared & presented by:
Anatomy of the Ear Prepared & presented by: Prof. Dr. Hassan M. Serry © Anatomy and Embryology department, ASU, Month/Year 12/2012
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By the end of this lecture, you should be able to:
ILOs By the end of this lecture, you should be able to: List parts of the ear. Describe parts of External ear: auricle & external auditory meatus and give their nerve supply and its applied anatomy. Describe roof, floor, and walls of Middle ear and enumerate its contents. Identify parts and function of auditory tube. Name parts of Internal ear: bony & membranous labyrinth.
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The Ear
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It is the organ of Hearing and also concerned with Equilibrium
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External Ear
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AURICLE
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EXTERNAL ACOUSTIC (AUDITORY) MEATUS
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1/3 2/3 24 mm in length
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It describes an S-shaped curve
Lateral Medial
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TYMPANIC MEMBRANE (EAR DRUM)
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about 10 mm in diameter it is obliquely directed making an angle of 55 with the floor of the meatus
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posterior anterior
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Middle Ear
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Epitympanic recess Tympanic cavity proper
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Posterior Anterior
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Anterior (carotid) wall
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Canal for Tensor tympani Bony part of Auditory tube Internal carotid artery
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Posterior(mastoid) wall
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Aditus to Mastoid antrum Pyramid
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Roof (tegmental) wall
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Tegmen tympani
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Floor (Jugular) wall
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Tympanic branch of XI Internal jugular vein
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Medial (Labyrinthine)
wall
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Promontory Prominence of Facial n. canal Fenestra vestibuli Fenestra chocleae Sinus tympani Tympanic plexus of ns.
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Lateral (membranous) wall
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CONTENTS OF TYMPANIC CAVITY
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Auditory Ossicles
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Malleus Lateral Incus Anterior Stapes Posterior Medial
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Muscles of tympanic cavity
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Action The tensor tympani and stapedius usually contract together in reflex response to sounds of fairly high intensity, exerting a 'protective damping effect before vibrations reach the internal ear The tensor pulls the tympanic membrane inwards to tense it and also pushes the stapes more tightly into the fenestra vestibuli. The stapedius muscle opposes the tensor in the latter action.
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Pharyngotympanic (Auditory) tube
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Tympanic caviry Pharyngotympanic tube 1/3 2/3 Pharynx 36 mm in length
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The internal ear (Labyrinth)
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The labyrinth is situated in the petrous part of the temporal bone, medial to the middle ear.
It consists of the bony labyrinth, comprising a series of cavities within the bone. and the membranous labyrinth, comprising a series of membranous sacs and ducts contained within the bony labyrinth. Labyrinth
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Bony Labyrinth Labyrinth
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Cochlea Vestibule Semicircular canals
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Vestibule Labyrinth
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Right bony labyrinth Anterolateral view
Semicircular canals Vestibule Posterior Anterior Oval window (Fenestra vestibuli) Scala vestibuli
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Right bony labyrinth Top view
Semicircular canals Aqueduct of vestibule Vestibule Lateral Medial Oval window (Fenestra vestibuli) Scala vestibuli
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Semicircular canals Labyrinth
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Right bony labyrinth Anterolateral view
Anterior semicircular canal Lateral semicircular canal Ampullae of semicircular canals Posterior Anterior. Posterior semicircular canal
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Semicircular canals Anterior Lateral Posterior
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Cochlea Labyrinth
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Cochlea (snail shell -shaped)القوقعة
It opens into the anterior part of the vestibule it consists of a central pillar, the modiolus, around which a hollow bony tube makes two and one half spiral turns Each successive turn is of decreasing radius so that the whole structure is conical. The apex faces anterolaterally and the base faces posteromedially The first basal turn of the cochlea is responsible for the promontory seen on the medial wall of the middle ear. Labyrinth
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Right bony labyrinth Anterolateral view
Cochlea Apex Basal turn Posterior Anterior.
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Section of cochlea Cochlea Modiolus Basal turn
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Internal auditory meatus
Section of cochlea Cochlea tube Scala vestibuli Spiral lamina Scala tympani Modiolus Internal auditory meatus
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Longitudinal section of cochlea
Cochlea tube Scala vestibuli Modiolus Scala tympani Spiral lamina Spiral ganglion
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Section of cochlea Basilar membrane Vestibular membrane
Scala vestibuli Modiolus Scala tympani Spiral ganglion Spiral lamina
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Membranous Labyrinth it is contained within the bony labyrinth but much smaller in size. It is filled with endolymph Its walls receive the branches of the vestibulocochlear nerve. Labyrinth
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Anterior semicircular duct Ampulla
Lateral semicircular duct Anterior semicircular duct Ampulla Endolymphatic duct and sack Dura mater Posterior semicirular duct Cochlear duct Utricle Utricosaccular duct Saccule Scala vestibuli Cochlear canaliculus Scala tympani Labyrinth
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Labyrinth
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Thank You
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