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