The Ear 1. External Ear Auricle or pinnae surrounds the ear Helix Lobule Anatomy of the Ear 2.

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The Ear

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External EarAuricle or pinnae surrounds the ear

HelixLobule

Anatomy of the Ear

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Anatomy of the Ear

External acoustic meatus Ceruminous glands produce waxHairSebaceous glands

Tympanic membraneSeparates the outer ear from the middle

earVibrates at the same frequency as the

sound wave

4Figure 17.20

Ear

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Auditory ossicles – lever system that transmits the sound wave to the inner earMalleus (hammer)Incus (anvil)Stapes (stirrup)

Oval window – transmits the coming sound to the inner ear

Middle ear- tympanic cavity

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Middle ear- tympanic cavity

Round window – secondary tympanic membrane

Auditory, Eustachian or Pharyngotympanic Tube – connects the middle ear with the nasopharynx

Otites media – inflammation of the middle ear. Myringotomy – lancing of the eardrum

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Inner Ear

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Bony or osseous labyrinth surrounds and protects membranous labyrinthPerilymph – aqueous fluid that fills the bony

labyrinthVestibule – involved in static equilibriumSemicircular canals – involved in dinamic

equilibriumLateral, anterior, posterior

Cochlea – responsible for hearing

Inner ear

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Inner ear

Membranous LabyrinthEndolymph – viscous fluid that fills the

ductsCochlear ducts – located in the scala

media Semicircular ducts – located in the

semicircular canalsVestibule – located inside of the vestibule

canal

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Inner Ear

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Organ of Corti – for hearingBasilar membrane – forms the floor of

the cochlear duct and supports the Organ of Corti

Tectorial membrane – overlies the Organ of Corti. It’s gel-like and is in contact with the stereocilia of the hair cell

Vestibular membrane – separates the scala vestibular from the scala media

Microscopic anatomy of Organ of Corti

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Scala vestibuli – filled with perilymph

Scala tympani – filled with perilymph

Scala media – filled with endolymph

Microscopic anatomy of Organ of Corti

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Sound localizationFrequency range

Frequency is perceived a pitch. The higher the frequency the higher the pitch

Tests of Hearing

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Tests of Hearing

Weber’s Test – determines:Sensorial deafness (Presbicusis)-

caused by damage of the neural structuresConduction deafness- cased by anything

that stops the sound conduction to the inner ear

Rinne testCompares bone and air conduction

hearing

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Tests of Hearing

AudiometryMeasures frequency in hertz Measures amplitude in decibels. Amplitude

is perceived as intensity or loudness of the sound

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Microscopic anatomy of Equilibrium Apparatus

Vestibular ApparatusDivided into utricle and sacculeMacula

Hair cellsOtolithic membrane

17Figure 17.23a, b, & d

Inner Ear

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Vestibular apparatus

Monitors static equilibrium Movement of the head when the body is

static Ups and downsStraight line changesPosture

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Microscopic anatomy of Equilibrium Apparatus

Semicircular canals and ductsAnterior, posterior and lateral Ampulla

Hair cellsCupula

20Figure 17.23a, b, & d

Inner Ear

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Semicircular canals and ducts

Monitor dynamic equilibrium Perception of the rotational orientation of

the head when the body is movingBoat riding

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Tests on equilibrium

Balance testWalk in straight line placing one foot

directly in front of the otherBarany test

Evaluates the semicircular canalsRotates the person sitting in a rotating

chair. Stop the rotation and observe if the person has nystagmus and vertigo

Nystagmus is normal after rotation onlyVertigo – dizziness and rotational

movement when the person is static

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Tests on equilibrium

Romberg’s testDetermines the integrity of the dorsal white

column of the spinal cordObserves swaying movements when the

person is standing erect and staring straight ahead

Role of vision on equilibrium