Transcript anatomy of the ear

ANATOMY OF THE EAR
Pinna
External Auditory Meatus
External Ear Canal
Tympanic Membrane
Middle Ear Walls
Middle Ear Function
Ossicles
Middle Ear Muscles
Energy Changes
Outer, Middle and Inner Ear
Vestibular Mechanism
Cochlea
Cochlea
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scala tympani—starts at round window and contains
perilymph
scala vestibuli—starts at the oval window and also
contains perilymph
helicotrema—found at the apex of the cochlea where
the perilymph from the scala tympani and the scala
vestibuli meet.
scala media (cochlear duct)—closed at base and at
the helicotrema end. This duct contains endolymph
which is the same fluid contained within the saccule,
utricle, and semicircular canals.
Cochlea
Coil of Cochlea
Scala Media
Cochlea (continued)
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Ductus reuniens—connects the
vestibular areas to the auditory
mechanism and allows the endolymph
to circulate between these two areas.
Basilar membrane—separates scala
tympani from scala media
Reisner’s membrane—separates scala
vestibuli from scala media
Organ of Corti
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Organ of Corti—end organ of hearing. Found in the scala media
Rods of Corti—form the tunnel of Corti. On each side of the
rods are found hairs arranged in an orderly fashion. One row of
inner hair cells (3,000) and three rows of outer hair cells
(12,000—15,000).
Tectorial membrane—hair cells are imbedded in this jelly-like
membrane after they pass through the reticular lamina.
Hensen cells—supportive to the hair cells
Stria vascularis—produces endolymph and is responsible for
getting oxygen and blood to the Organ of Corti. Found on the
lateral wall of the cochlear duct.
Organ of Corti
Cochlea Unrolled
Frequency Specific
Cochlea
Cochlea is frequency specific - basal
end is responsible for the high
frequencies and apical end controls low
frequencies.
Auditory Nerve
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Internal auditory Meatus (IAM) - nerve
fibers pass from the modiolus through
the IAM to the base of the brain.
VIII Nerve is comprised of 30,000 nerve
fibers from the cochlea + 20,000 from
the vestibular and travel through the
IAM to the brain stem.
Auditory Pathways
Auditory Pathways
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Cochlea hair cells
Auditory nerve fibers
Cochlear nucleus
Trapezoid body
Superior olivary complex
Lateral lemniscus
Inferior coliculus
Medial geniculate body
Auditory cortex