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The Ear
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Anatomy of the Ear
 External Ear
Auricle or pinnae surrounds the ear
Helix
Lobule
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Anatomy of the Ear
External acoustic meatus
Ceruminous glands produce wax
Hair
Sebaceous glands
Tympanic membrane
Separates the outer ear from the middle
ear
Vibrates at the same frequency as the
sound wave
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Ear
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Figure 17.20
Middle ear- tympanic cavity
 Auditory ossicles – lever system that
transmits the sound wave to the inner ear
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
 Oval window – transmits the coming sound
to the inner ear
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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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Inner ear
 Bony or osseous labyrinth surrounds and
protects membranous labyrinth
Perilymph – aqueous fluid that fills the bony
labyrinth
Vestibule – involved in static equilibrium
Semicircular canals – involved in dinamic
equilibrium
Lateral, anterior, posterior
Cochlea – responsible for hearing
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Inner ear
 Membranous Labyrinth
Endolymph – viscous fluid that fills the
ducts
Cochlear ducts – located in the scala
media
Semicircular ducts – located in the
semicircular canals
Vestibule – located inside of the vestibule
canal
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Inner Ear
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Microscopic anatomy of Organ of Corti
 Organ of Corti – for hearing
Basilar 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
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Microscopic anatomy of Organ of Corti
Scala vestibuli – filled with perilymph
Scala tympani – filled with perilymph
Scala media – filled with endolymph
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Tests of Hearing
 Sound localization
 Frequency range
Frequency is perceived a pitch. The higher
the frequency the higher the pitch
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Tests of Hearing
 Weber’s Test – determines:
Sensorial deafness (Presbicusis)caused by damage of the neural structures
Conduction deafness- cased by anything
that stops the sound conduction to the
inner ear
 Rinne test
Compares bone and air conduction
hearing
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Tests of Hearing
 Audiometry
Measures 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 Apparatus
Divided into utricle and saccule
Macula
Hair cells
Otolithic membrane
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Inner Ear
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Figure 17.23a, b, & d
Vestibular apparatus
 Monitors static equilibrium
 Movement of the head when the body is
static
Ups and downs
Straight line changes
Posture
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Microscopic anatomy of Equilibrium
Apparatus
 Semicircular canals and ducts
Anterior, posterior and lateral
Ampulla
Hair cells
Cupula
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Inner Ear
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Figure 17.23a, b, & d
Semicircular canals and ducts
 Monitor dynamic equilibrium
Perception of the rotational orientation of
the head when the body is moving
Boat riding
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Tests on equilibrium
 Balance test
Walk in straight line placing one foot
directly in front of the other
 Barany test
Evaluates the semicircular canals
Rotates the person sitting in a rotating
chair. Stop the rotation and observe if the
person has nystagmus and vertigo
Nystagmus is normal after rotation only
Vertigo – dizziness and rotational
movement when the person is static
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Tests on equilibrium
 Romberg’s test
Determines the integrity of the dorsal white
column of the spinal cord
Observes swaying movements when the
person is standing erect and staring
straight ahead
 Role of vision on equilibrium
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