L11 - The auditory pathway Flashcards
what is the flat part of the temporal bone called?
squamous
what is the rough part fo the temporal bone called?
petrous
what is the functions of the external ear?
receives sound waves
what is the functions of the middle ear?
sound waves are changed to mechanical waves - contains ossicles
what is the functions of the inner ear?
changes mechanical waves to electrical waves - contains cochlea
how big is the external Canal?
2-3cm - transmits sound waves towards the tympanic membrane
what is the function of the tympanic membrane?
vibrates with sound waves separates external from middle ear
which structure separates the external ear from the middle ear?
tympanic membrane
what structure is commonly known as the “ear drum”?
tympanic membrane
how does the middle ear communicate with the nasopharynx?
via eustachian (Auditory tube)
what are the 3 ossicles?
malleus incus stapes
what is the function of the ossicles?
vibrate to amplify sound and transfer to the middle. ear
what happens to the ossicles with age?
become calcified with age - less flexible - conductive hearing loss
what structures does the Eustachian tube connect?
nasopharynx to middle ear
what is the function of the Eustachian tube?
- drains middle ear into nasopharynx - preventing accumulation of fluids - ventilates middle ear - equalise pressure between external environment and inside head
why are infants more likely to get ear infections than adults?
- Eustachian tube more horizontal (adults more vertical) - easy route for bacteria from nasopharynx /ear
why is the middle ear a “high risk space” for infection?
- connected to nasopharynx (prone to infection) - connected to mastoid air cells (infection can spread to cranial fossa) - internal jugular vein lies inferior (thrombosis risk) - internal carotid artery lies anterior (pulsatile tinnitus) - traversed by chordates tympani and facial canal (could become infected and spread to facial muscles)
why does the middle ear being connected to the nasopharynx make it a high risk space?
prone to infection
why does the middle ear being connected to mastoid air cells make it a high risk space?
infection may spread to middle cranial fossa
if there was an infection of the middle ear where may is spread?
middle cranial fossa (via mastoid air cells) chordates tympani facial canal
why does the internal jugular vein lying inferior to the middle ear make the middle ear a high risk space?
risk of thrombosis
why does the internal carotid lying anterior to the middle ear make the middle ear a high risk space?
link to pulsatile tinnitus
what is pulsatile tinnitus?
a rhythmical noise that usually has the same rate as the heart. This is easily checked by feeling the pulse at the same time as listening to the tinnitus.
what is the stapedius reflex?
involuntary muscle contraction of the stapedius and tensor tympani of the ossicles in the middle ear - in response to high-intensity sound - used to asses middle ear function
what part of the year is located in the petrous part of the temporal bone?
inner ear
the inner ear is made up of which 2 special sense organs?
vestibular system (balance and equilibrium) cochlea (hearing)
how is the spiral ganglia of the cochlear system tonotopically organised?
tip: lower freq sounds base: higher freq sounds
the petrous part of the temporal bone has a series of fluid filled cavities - what are they?
bony (outer) labyrinth membranous (inner) labyrinth
what fluid is contained in the bony (outer) labyrinth of the petrous part of the temporal bone?
perilymph - resembles extra-cellular fluid
what fluid is contained in the membranous (inner) labyrinth of the petrous part of the temporal bone?
endolymph - resembles intracellular fluid
which fluid filled cavity of the petrous part of the temporal bone contains fluid that resembles extra-cellular fluid?
bony (outer) labyrinth perilymph - resembles extra-cellular fluid
which fluid filled cavity of the petrous part of the temporal bone contains fluid that resembles intra-cellular fluid?
membranous (inner) labyrinth endolymph - resembles intracellular fluid