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Transcript
Anatomy of the Ear
Chapter 8
Functions
• Hearing
• Equilibrium and Balance
External Ear
• Pinna (auricle)
– Collects & directs sound waves
into the auditory canal
• External Auditory Canal
– Short, narrow chamber that
directs sound waves to the
tympanic membrane
• Tympanic membrane
(eardrum)
– Sound waves vibrate the
membrane
Middle Ear (tympanic cavity)
• Air filled cavity
• Auditory (Eustachian) tube
– Connects middle ear to throat
– helps equalize pressure in ear
Did you know…
In infants, the
auditory tube is
more horizontal,
therefore, when
children get sore
throats they usually
are more prone to
ear infections.
• Spanned by ossicles which transmit the
vibratory motion of the eardrum to the oval
window and the fluids of the inner ear
– Malleus (hammer)
– Incus (anvil)
– Stapes (stirrup)
Inner Ear
• Osseous- bony chambers filled with fluid
– Cochlea
• Contains organ of Corti which contains hair cells
(hearing receptors) that transmits the impulses to the
vestibulocochlear nerve and finally the temporal lobe
of the brain
– Vestibule
– Semicircular canals
Hearing Sequence of Events
1. Pinna
2. External auditory tube
3. Tympanic membrane
4. Malleus
5. Incus
6. Stapes
7. Oval window
8. Organ of Corti in Cochlea
9. Hairs cells
10. vestibulocochlear nerve
Equilibrium
• Static (at rest)
– Maculae (receptors) in vestibule report the
position of the head to the pull of gravity when
the body is not moving
– Maculae transmit message to vestibular nerve
that tells cerebellum your head’s position in space
(balance)
• Dynamic
– Dynamic equilibrium receptors in semicircular
canal respond to angular or rotatory movements
of the head and transmit message to cerebellum
via the vestibular nerve
Deafness
• Hearing loss of any degree
• 2 kinds:
– Conduction deafness
• Something interferes with the conduction of sound
vibrations to the fluids of the inner ear
– Caused by:
» Mechanical factors such as build up of earwax, fusion of
ossicles, ruptured ear drum
• Sensorineural deafness
– Degeneration or damage to the receptor cells in
the organ of Corti, the cochlear nerve or to
neurons in the auditory cortex of the brain
– Due to problem of nervous system structures
Did you know….
Hearing Aids only improve the hearing of patients
with conduction deafness.