The External and Middle Ear Flashcards
what is the function of the external ear
collect soundwaves and funnels them into the external acoustic meatus
what nerves supply the external ear
CN VII(facial nerve), CN V3(auriculotemporal), C2,3(via lesser occipital nerve and greater auricular nerve)
what is the external ear called
the Pinna or Auricle
what is the main function of the middle ear and tympanic cavity
to conduct soundwaves in air, by bone conduction mechanism of hearing, towards fluid filled cavities of inner ear
what are the auditory ossicles lateral to medial, and therefore from largest to smallest
Malleus(hammer), Incus(anvil) and Stapes(stirrup)
found in middle ear, in tympanic cavity
where do the tensor tympani muscle and stapedius muscle run from
tensor tympani muscle = cartilaginous portion of eustachian tube to handle of malleus
stapedius muscle = from pyramidal eminence to neck of stapes
what is the role of the tensor tympani muscle in the middle ear
dampens sound by reducing vibration of tympanic membrane
what is the role of the stapedius muscle in the middle ear
dampens sound by reducing vibrations of stapes on oval window
what are tensor tympani and stapedius muscle innervated by
tensor tympani = CN V3
stapedius = CN VII
what is the typical middle ear pressure, and how is this pressure achieved
typically equal to atmospheric air pressure
palate muscles open the eustachian tube to equalise pressure
what happens to the tympanic membrane when the tympanic cavity air pressure is greater or lower than atmospheric air pressure
greater = tympanic membrane is pushed out lower = tympanic membrane is pushed in
what results from inequality between tympanic and atmospheric air pressures
reduced vibration of ossicles and possibly barotrauma
describe where the eustachian(auditory) tube runs
runs from the anterior wall of the middle ear cavity to the nasopharynx
(therefore some inflammation from middle ear can spread to pharynx)
what is responsible for general sensory innervation of the middle ear
CN IX, via tympanic plexus
in the tympanic cavity what is the role of the oval and round windows
oval window = received footplate of the stapes
round window = dissipates the forces/vibrations from the cochlea
