Download Vibration of the stapes at the oval window causes the perilymph in

Welcome
The Ear
The ear functions to provide hearing
and equilibrium. It has three regions
THE THREE
OSSICLES
(BONES) ARE
LATIN FOR
HAMMER
THE OUTER EAR
ANVIL AND
THE INNER
STIRRUP DUE
COMPOSED OF
EAR
TO THEIR
PINNA
COMPOSED OF
SHAPES.
THE
AUDITORY CANAL
THEY ARE THE
MIDDLE SACCULE CLASSIFIED AS
SMALLEST
EAR
UTRICLE THE VESTIBULE
BONES AND
COMPOSED OF
ARE FULLY
TYMPANIC MEMBRANE
SEMICIRCULAR CANALS
DEVELOPED
OSSICLES - MALLEUS INCUS STAPES
AT BIRTH
COCHLEA
EUSTACHIAN TUBE
Did you know?
• Cats are able to move their pinna (which collect
and concentrate sound) toward the source
making them able to hear even when facing a
different direction.
• Humans do not have this ability, yet the three
muscles that turn the pinna in the cat are still
found surrounding the human pinna.
• Evolutionary biologists call it a vestigial structure.
So do like Mickey Mouse says, because you really
can wiggle your ears
This little muscle attached
The tympanic
to the stapes can pull it
membrane
away from the oval window
vibrates with
sound.
The ossicles
transfer the
vibrations to
the oval
window of
the cochlea
The stapes
hits the oval
window
with a force
3x greater
The Eustachian tube equalizes air
than the
pressure in the middle ear cavity.
eardrum
Hey, my ears just popped!
vibration
The Middle Ear
Did you know?
Consistent loud blaring sounds
cause the stapedius muscle to
retract in a reflex that prevents
damage to the inner ear. Just don’t
expect it to work on a sudden
sound as it takes time for this reflex
to occur!
The Inner Ear
The utricle and saccule are involved in static equilibrium.
They are shown here in between the cochlea and
semicircular canals.
They contain otoliths
suspended in a
endolymph liquid and
use these to determine
the head orientation
Notice the fluid
perilymph shown in the
picture is red
The fluid endolymph is
shown in purple
Endolymph is found
in the cochlear duct
Perilymph is found in
the vestibular and
tympanic canals
shown
FLUID FACTS
• Endolymph or cochlear fluid is involved in
equilibrium information and is high in
potassium. (Found in the membranous
labyrinth)
• Perilymph transfers sound information and is
similar to cerebrospinal fluid in consistency
with high sodium. (Found in the bony
labyrinth)
Otoliths and static equilibrium
The otoliths shown at the left are small
calcium carbonate granules that can
move fluid based on how they are
affected by gravity.
When the head changes position with
respect to gravity, the gelatinous fluid
moves stimulating the hair cells. This
registers in your brain and tells you if
you are upside down, right side up, or
sideways.
The
Semicircular
Canals
These fluid filled canals
establish dynamic
equilibrium
These three canals
extend in all three
dimensions to
register movement
when fluids shift due
to motion like:
ROTATION
ACCELERATION
THE AMPULLA
The ampulla at the bottom
of each of the semicircular
canals contain cilia
attached to hair cells.
When the endolymph
moves, the cilia bend the
hair cells transmitting
nerve impulses.
MOTION SICKNESS?
Overstimulation of the
hair cells from rapid and
continuous fluid
movement
AMPULLA
Like whoa,
my ampulla
hair cell
cilia are
being
stimulated!
The Cochlea
Vibration of the stapes at
the oval window causes the
perilymph in the tympanic
canal to move.
The cochlea is coiled and
the canals, being more
narrow and rigid at the
top, register the higher
frequency sound.
Once the perilymph moves
past the top of the coil, it
enters the vestibular canal
and moves to the round
window which releases the
pressure wave.
ORGAN OF
CORTI
When the perilymph in
the tympanic canal
moves, the basiliar
membrane moves.
The hair cells connect
this membrane to the
stationary tectorial
membrane and send a
signal through the
cochlear nerve
Vestibular canal
Tympanic canal
FUN FACT
• When you hear a mosquito in your room the
energy is only one quadrillionth of a watt
With hearing like that its a wonder I ever get any
sleep at all!
The end