Download Anatomy and Physiology of the Ear Anatomy and Physiology of the Ear

Anatomy and Physiology
of the Ear
Eslam Osman, M.D.,F.R.C.S (ORL, H&N Surgery)
02/07/08
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Divisions Of The Ear
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External Ear
Middle Ear
Inner Ear
Central Auditory Nervous System
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Structures of the Outer Ear
Pinna
„ Collect sound
„ Localization
„ Resonator
„ Protection
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External Auditory Canal
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Extends from the pinna to the
tympanic membrane
1 1/2 inch in length
Protects the eardrum
Wax
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Structures of the Middle Ear
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Tympanic Membrane
Tympanic Cavity
Ossicles
Middle Ear Muscles
Eustachian Tube
Mastoid
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Tympanic Membrane
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The eardrum separates the outer ear
from the middle ear
Creates a barrier that protects the
middle and inner areas from foreign
objects
The eardrum vibrates in response to
sound pressure waves.
Changes acoustic energy into
mechanical energy
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Ossicles
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Malleus (hammer)
Incus (anvil)
Stapes (stirrup) smallest bone of the
body
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Middle Ear Muscles
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Tensor tympani
• Attached to malleus
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Stapedius
• Attached to stape
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Middle Ear Muscle Function:
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Help maintain ossicles in proper position
Protect inner ear from excessive sound levels
This protective reflex termed "acoustic reflex"
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Eustachian Tube
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The ET connects the front wall of the
middle ear with the nasopharynx
It operates like a valve, which opens
during swallowing and yawning
It equalizes the pressure on either
side of the eardrum, which is
necessary for optimal hearing.
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Mastoid
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Bony ridge behind the auricle
Connect with middle ear
Can get infected ( Mastoiditis)
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Function of Middle Ear
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Conduction
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Protection
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Transducer
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Amplifier
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Amplifier
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The middle ear enhances the transfer
of acoustical energy in two ways:
• The area of the eardrum is about 17
times larger than the oval window
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The effective pressure (force per unit area)
is increased by this amount.
• The ossicles produce a lever action that
further amplifies the pressure
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Structures of the Inner Ear
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Cochlea
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Vestibule
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Semicircular canals
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Cochlea
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Snail-shaped organ
with a series of
fluid-filled tunnels
converts
mechanical energy
into electrical
energy
It contain Organ of
Corti ( end organ of
hearing)
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Traveling Waves
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Vestibular System
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Consists of vestibule and three semicircular canals
Shares fluid with the cochlea
Controls balance
No part in hearing process
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Central Auditory Pathway
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Pathway between
cochlea and
auditory cortex
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Cochlear nerve
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Cochlear nucleus
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Causes of Tinnitus
Local causes
Every ear disease can be associated
with deafness
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General Causes
Cardiovascular disease
Neurological conditions
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Classification of Tinnitus
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Unilateral or bilateral
Subjective or objective
Pulsatile or non pulsatile
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Key Points in History
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Accompanying ear disease
History of noise exposure
Trauma
Ototoxic medications
Systemic Diseases
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THANK YOU
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