SEM2 The Ear Anatomy and Physiology

pharyngotympanic tube

• connects middle ear to throat

• opens when you yawn or swallow, which equalizes pressure in middle ear ( eardrum will only function if pressure inside/out is equal )

What are the smallest bones in the body?

1. malleus

2. incus

3. stapes

Inner ear

• maze of body chambers called labyrinth

  • 3 divisons

    1. vestibule

    2. cochlea

    3. semicircular canals

• labyrinth filled with perilymph ( fluid )

hearing

• vibrating air particles

• sound waves are directed into the auditory canal ( helped by pinna )

• sound waves reach the eardrum, causing it to vibrate

• vibrations are passed through the malleus, incus, then stapes

• the stapes then presses on the oval window of the cochlea, which contains fluid

organ of corti

• within the cochlea converts vibrations to a nerve impulse

• fluid within cochlea starts to move

• movement causes the tectorial membrane to move

• membrane then causes the hair ( receptors ) on basilar membrane to move

• the hairs then transmit a nerve impulse to the cochlear nerve

equilibrium ( balance )

• involves vestibule and semicircular canals

• one branch is responsible for static equilibrium, the other, dynamic equilibrium

static equilibrium

• maculae receptors in the membrane of vestibule

• each macula is a patch of receptor cells with “ hairs “ embedded in otolithic membrane

• membrane contains otoliths ( calcium salts )

• when head moves up+down, otoliths move

• causes gel to move

• gel moves hair

• hair sends impulses along the vestibular nerve to the cerebellum

• these receptors respond to gravity ( up+down )

dynamic equilibrium

• receptors in semicircular canals

• respond to angular, rotary head movements

• receptor region called crista ampullaris

• consists of tuft of hair cells and cupula ( gel cap )

• when head moves, endolymph ( fluid ) lags behind

• as cupula drags against, it bends

• stimulates the hair cells which creates an impulse to send up the vestibular nerve to cerebellum

What is number 1?

pinna

what is number 2?

auditory canal

what is number 3?

tympanic membrane

what is number 5?

round window

what is number 6?

phanymgotypanic tube

what is number 7?

cochlea

what is number 9?

semicircular canals

what is number 10?

stapes

what is number 12?

incus

what is number 13?

malleus

what is number 15?

outer ear

what is number 16?

middle ear

what is number 17?

inner ear

where is oval window?

in the middle of stapes

where is vestibule?

to the left of cochlea