1 EAR Lecture for BDS students only By Prof. Ansari 11/18/2015

2 Objectives  Gross anatomy of External ear.  Gross anatomy of Middle ear.  Gross anatomy of Internal ear.  Applied anatomy

3 EAR

4 Objectives  Parts of external ear,  Middle ear cavity, & contents.  Internal ear  Applied anatomy.

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6 The external ear has Pinna & external acoustic meatus.

The external ear and external acoustic meatus  Is made up of elastic cartilage.  The extrinsic muscles of ear are auricularis anterior, auricularis superior and auricularis posterior.  These muscles are non functional and are supplied by facial nerve.  In lower animals these muscles carry the pinna in the respective directions to collect the sound waves. 7

The external acoustic meatus  It is partly cartilagenous and partly bony.  At the medial end it has tympanic membrane closing the canal.  The meatus is lined by stratified squamous epithelium with wax glands.  Developmentally it is from the first cleft. 8

THE NORMAL TYMPANIC MEMBRANE 9

10 The middle ear  It is a six sided chamber, it has a roof, floor, ant.wall, post. Wall, medial wall & lateral wall.  Roof is formed by tegmen tympani.  Floor is formed by jugular bulb& carotid canal.  Ant. Wall has two tubes, canal for tensor tympani muscle & auditory tube.

11 Walls of middle ear  The posterior wall has aditus ad- antrum, canal that communicates with the mastoid air cells, which are present in mastoid process.  Medial wall has round window and oval window, the foot plate of stapes fits into the oval window.  The lateral wall is formed by tympanic membrane.

12 Middle ear contents seen through the tympanic membrane

13 Contents of middle ear  Muscles are:- 1. Tensor tympani, 2. Stapedeus.  Nerves are:- 1. Tympanic plexus, 2. chorda tympani nerve, 3. facial nerve.  Bones are:- 1. Malleus, 2. Incus, 3. Stapes.

14 The middle ear cavity

15 Walls of the middle ear Tegmen tympani Mastoid Air cells Jugular bulb Tensor tympani Auditory tube Carotid canal Oval window

THE EAR OSSICLES  MALEUS  INCUS AND  STAPES 16

The contents of middle ear after opening from roof 17

18 Internal ear  It is in the petrous part of temporal bone.  It lodges cochlea, vestibule and semicircular canals.  It communicates with the middle ear through two windows, oval and round.

19 Parts of internal ear

20 Development of external ear  Six ear hillocks develop around the first pharyngeal cleft.  They coalesce with each other and form the pinna.  The external acoustic meatus develops from first pharyngeal cleft.  The lateral surface of tympanic membrane develops from the ectoderm of first cleft.

21 Development of middle ear  The tympanic cavity develops from the first pharyngeal pouch, endoderm.  The malleus, incus ossicles develop from the first pharyngeal arch.  The tensor tympani is also from first arch derivative.  The stapes and stapedius muscle develops from second arch mesoderm

22 The internal ear development  It is ectodermal, from otic placode.  Ear is an example of organ developing from all three germ layers.

23 Applied anatomy  There are two functions done by ear,  Hearing and balancing/equilibrium.  Acoustic neuroma is a tumour of auditory nerve, which causes nerve deafness.

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25 Review of ear

References Essential Clinical Anatomy Keith L. Moore 4 th edition Page nos

A 36 year old person develops ipsilateral sensorineural hearing loss/deafness, disturbed sense of balance and altered gait, vertigo with associated nausea and vomiting.  His CT of head region showed the following picture.  Acoustic neuroma was diagnosed. 27