Anatomy and Physiology of the Ear - Patients & Visitors · 02/07/08 Tinnitus Support Group 44...

02/07/0802/07/08 Tinnitus Support GroupTinnitus Support Group 11

Anatomy and Physiology of the Ear

Anatomy and Physiology Anatomy and Physiology of the Earof the Ear

Eslam Osman, M.D.,F.R.C.S (ORL, H&N Surgery)Eslam Osman, M.D.,F.R.C.S (ORL, H&N Surgery)


Divisions Of The EarDivisions Of The EarDivisions Of The Ear

External EarExternal EarMiddle EarMiddle EarInner Ear Inner Ear Central Auditory Nervous SystemCentral Auditory Nervous System



Structures of the Outer Ear Structures of the Outer Ear

PinnaPinnaCollect soundCollect soundLocalizationLocalizationResonatorResonatorProtectionProtection


External Auditory CanalExternal Auditory Canal

Extends from the pinna to the Extends from the pinna to the tympanic membranetympanic membrane1 1/2 inch in length1 1/2 inch in lengthProtects the eardrumProtects the eardrumWaxWax


Structures of the Middle EarStructures of the Middle Ear

Tympanic Membrane Tympanic CavityOssiclesMiddle Ear MusclesEustachian TubeMastoid


Tympanic MembraneTympanic Membrane

The eardrum separates the outer ear The eardrum separates the outer ear from the middle earfrom the middle earCreates a barrier that protects the Creates a barrier that protects the middle and inner areas from foreign middle and inner areas from foreign objectsobjectsThe eardrum vibrates in response to The eardrum vibrates in response to sound pressure waves. sound pressure waves. Changes acoustic energy into Changes acoustic energy into mechanical energymechanical energy


OssiclesOssicles

Malleus (hammer)Malleus (hammer)Incus (anvil)Incus (anvil)Stapes (stirrup) smallest bone of the Stapes (stirrup) smallest bone of the bodybody


Middle Ear MusclesMiddle Ear MusclesTensor tympaniTensor tympani•• Attached to malleusAttached to malleus

StapediusStapedius•• Attached to stapeAttached to stape

Middle Ear Muscle Function:Middle Ear Muscle Function:•• Help maintain ossicles in proper positionHelp maintain ossicles in proper position•• Protect inner ear from excessive sound levels Protect inner ear from excessive sound levels •• This protective reflex termed "acoustic reflex"This protective reflex termed "acoustic reflex"


Eustachian TubeEustachian Tube

The ET connects the front wall of the The ET connects the front wall of the middle ear with the nasopharynx middle ear with the nasopharynx It operates like a valve, which opens It operates like a valve, which opens during swallowing and yawningduring swallowing and yawningIt equalizes the pressure on either It equalizes the pressure on either side of the eardrum, which is side of the eardrum, which is necessary for optimal hearing.necessary for optimal hearing.


MastoidMastoid

Bony ridge behind the auricleBony ridge behind the auricleConnect with middle earConnect with middle earCan get infected ( Mastoiditis)Can get infected ( Mastoiditis)


Function of Middle EarFunction of Middle Ear

ConductionConduction

ProtectionProtection

TransducerTransducer

AmplifierAmplifier


AmplifierAmplifier

The middle ear enhances the transfer The middle ear enhances the transfer of acoustical energy in two ways: of acoustical energy in two ways: •• The area of the eardrum is about 17 The area of the eardrum is about 17

times larger than the oval windowtimes larger than the oval windowThe effective pressure (force per unit area) The effective pressure (force per unit area) is increased by this amount. is increased by this amount.

•• The ossicles produce a lever action that The ossicles produce a lever action that further amplifies the pressurefurther amplifies the pressure


Structures of the Inner EarStructures of the Inner Ear

CochleaCochlea

VestibuleVestibule

Semicircular canalsSemicircular canals


CochleaCochleaSnailSnail--shaped organ shaped organ with a series of with a series of fluidfluid--filled tunnelsfilled tunnelsconverts converts mechanical energy mechanical energy into electrical into electrical energyenergyIt contain It contain Organ of Organ of Corti Corti ( end organ of ( end organ of hearing)hearing)


Traveling WavesTraveling Waves


Vestibular SystemVestibular System

Consists of vestibule and three semiConsists of vestibule and three semi--circular canalscircular canalsShares fluid with the cochleaShares fluid with the cochleaControls balanceControls balanceNo part in hearing processNo part in hearing process


Central Auditory PathwayCentral Auditory Pathway

Pathway between Pathway between cochlea and cochlea and auditory cortexauditory cortex

Cochlear nerveCochlear nerve

Cochlear nucleusCochlear nucleus


Causes of TinnitusCauses of Tinnitus

Local causesLocal causesEvery ear disease can be associated Every ear disease can be associated

with deafnesswith deafness

General CausesGeneral CausesCardiovascular diseaseCardiovascular diseaseNeurological conditionsNeurological conditions


Classification of TinnitusClassification of Tinnitus

Unilateral or bilateralUnilateral or bilateralSubjective or objectiveSubjective or objectivePulsatile or non pulsatilePulsatile or non pulsatile


Key Points in HistoryKey Points in History

Accompanying ear diseaseAccompanying ear diseaseHistory of noise exposureHistory of noise exposureTraumaTraumaOtotoxic medicationsOtotoxic medicationsSystemic DiseasesSystemic Diseases


THANK YOUTHANK YOU

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Anatomy and Physiology of the Ear - Patients & Visitors · 02/07/08 Tinnitus Support Group 44...

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