Transcript The Ear - Downey Unified School District

Damaris Alas
Lusine Zhamharyan
Matt Marquez
Period 3
• Made up of three parts
• Outer ear (external)
• Middle ear
• Inner ear
• Pinna (outer ear cartilage)
• External Auditory Canal
• Lined with hairs and ceruminous
glands, which prevent objects
and insects from entering.
• Both funnel sound waves
towards the tympanic
membrane (eardrum),
causing it to vibrate.
• Air filled space located in the
temporal bone of the skull
• Contains 3 small auditory bones:
•
•
•
Malleus
Incus
Stapes
• Auditory Tube
• Drains fluid
• Adjusts ear pressure
• Inter-articulated bones of
the middle ear that
amplify the vibration of
the eardrum and send
them to the internal ear
• Attached by ligaments
• Malleus attached to ear
drum
• Stapes attached to oval
window of inner ear
• The auditory tube maintains equal pressure in the ear
• Does this by:
 Draining fluid from the middle ear into the throat
 Allows the air to pass between the tympanic cavity
and the outside of the body by way of the throat and
mouth
• Tympanic Reflex
• Involuntary muscle
contractions after loud
sounds
• Ossicles are pulled on
causing them to become
more rigid and less
effective
• Vibrations are dampened
• Composed of a labyrinth
• Osseous Labyrinth (Bony)
• Secretes Perilymph
• Membranous Labyrinth
• Lies within the osseous
• Contains Endolymph
• Main Structures:
• Cochlea
• Semicircular Canals
• Vestibule
• Shaped like a snail shell
• Bony labyrinth is divided in
two
• Upper: Scala Vestibuli
• Oval Window to the apex
• Vestibular Membrane
• Lower: Scala Tympani
• Apex to the round window
• Basilar Membrane
• Both connected by helicotrema
• Membranous labyrinth lies in
the middle, called the Scala
Media (cochlear duct)
• Houses the organ of
Corti
• 16,000 hearing receptor
hair cells
• Lies on the upper surface
of the basilar membrane
• Hair cells extend into the
cochlear duct
• Carries the signal into the brainstem and synapses in
the cochlear nucleus
• From there the auditory information splits into motion
and form procession
• Auditory nerve fibers going to the ventral cochlear
nucleus synapse on their target cells with giant, hand
like terminals
• Two streams:
• Cells project to a collection of nuclei in the
medulla called the superior olive
• Vestibulocochlear
• located in the internal auditory canal
• responsible for both hearing and balance and
brings information from the inner ear to the brain
• Two special organs help the nerve function
properly:
• cochlea and vestibular apparatus
• Comes from 2 senses:
• Static Equilibrium
• Senses position of
the head
• Maintains stability
and posture
• Dynamic Equilibrium
• Senses motion
• Aids in maintaining
balance
• Comes from:
• Utricle and Saccule in Vestibule
• Contain Macula
• Hair cells which act as
sensory receptors
• Covered in layer of a
gelatinous matrix
• Otoliths
embedded on
surface
• Weigh down
on membrane
making it
more
responsive to
changes
• Comes from:
• Ampullae in
semicircular canals
• Communicate with the
utricle
• Contain Crista
Ampullaris
• Also contains hair
cells that extend
into a gelatinous
matrix (cupula)
Outer
Ear
• Sound waves enter the pinna
and travel down the auditory
canal
• The waves strike the ear drum
• The ear drum passes the waves
onto the auditory ossicles
Middle
(malleus, incus, & stapes) which
amplify the waves
Ear
Inner
Ear
• The waves enter the oval
window and pass through the
cochlea
• In the cochlea, the waves
trigger the hair receptor cells
from the organ of corti
• The organ of corti passes the
signal onto the cochlear nerve
which goes all the way up into
the auditory cortex, where it’s
processed.
• The waves continue on, out the
round window
• Can be:
• Acquired
• Picked up, and caused by outside factor
• Exposed to intense, pure tone
• Inherited
• Born with
• More than 100 types
• One in a thousand newborn are deaf
because of genetic defects
• 2 Types:
• Sensorineural
• Damage to the cochlea or auditory nerve
• Conductive:
• Interference with transmission of
vibrations in inner ear
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<http://www.bioon.com/bioline/neurosci/course/audvest.html>.
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<http://www.innerbody.com/image_nerv13/nerv128-new.html>.
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<http://www.enchantedlearning.com/subjects/anatomy/ear/>.
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<http://wps.aw.com/bc_goodenough_boh_4/177/45511/11650899.cw/index.html>.
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