the ear Flashcards
what are the three components of the external ear?
auricle
external auditory meatus
external surface of the tympanic membrane
what are the 4 components of the internal ear?
internal surface of the tympanic membrane
tympanic cavity
ossicles
pharyngotympanic tube
what are the 6 components of the inner ear?
auditory apparatus
vestibular apparatus
internal auditory meatus
vestibulochochlear nerve
oval window
round window
what forms the boundary between the external and middle ear?
the tympanic membrane
where do the middle and inner ear communicate?
at the oval and round window
what is the external ear made of?
elastic cartilage
what is the function of the auricle?
the auricle functions to catch sound waves and funnel them towards the external auditory meatus
where does the auricle receive arterial supply from?
from branches of the external carotid artery
explain how sound waves are passed to the middle ear
the tympanic membrane vibrates in response to sound waves hitting the external surface. the malleus ossicle bone attaches to the tympanic membrane and so as the membrane vibrates so does the malleus. this transmits the energy from the sound into a physical energy which can then be passes deeper in the middle ear
explain the relation of the ossicles
the handle of the malleus sits on the tympanic membrane
the malleus articulates / the incus bone
the incus bone articulates w/ the stapes
what joints are present between the ossicle bones?
plane synovial joins
how is sound transmitted to the inner ear?
it passes between the ossicles until it reaches the footplate of the staples which rests against the oval window where it passes through and then deeper into the inner ear
what is the oval window?
a membrane covered hole that leads to the inner ear
what are the two small muscles in the middle ear?
tensor tympani
stapedius
what is the function of tensor tympani and stapedius?
act to dampen the sound being passed from the ossicles to the more delicate structures of the inner ear
what is the pyramid of the inner ear?
a small bulge of bone
how does the facial nerve enter the temporal bone?
via the internal auditory meatus
explain the courses of the facial nerve through the temporal bone
it passes through the petrous temporal bone until it exits the bone at the stylomastoid foramen
where does the facial nerve divide into its branches that supply the muscles of facial expression?
at the parotid gland
where does the chords tympani branch from?
the facial nerve
where does the chords tympani join the lingual nerve?
in the infratemporal fossa
where does the auditory tube pass from / to?
it passes from the lateral wall of the nasopharynx (one either side) to open into the middle ear
why is the medial part of the auditory tube cartilaginous?
to provide attachment for salpingopharyngeus and tensor and levator veli palatini
explain the arterial supply to the middle ear
branches from both the external and internal carotid artery supply blood to the middle ear
explain what happens after the stapes vibrates in the oval window
this creates movement of the fluid of the bony and membranous labyrinths which reach the special sense of hearing and balance cells housed in the membrane
what is the function of the cochlea?
the cochlea houses the cells that provide the special sense of hearing
how do sound waves reach the round window?
the waves pass down the Scala tympani until it reaches the round window
what is the final step of the perception of sound?
the cells of the organ of corti (spiral organ) detect movement and transform it into electrical energy (a nerve impulse) which is then passed into the cochlear nerve. this nerve carries the nerve moulds to the brain to be interpreted as dif sounds by the auditory cortex
how is balance detected?
the semi circular canals of the bony labyrinth house the semi circular ducts of the membranous labrynth. these ducts house motion sensor cells in their ampullae
motion is detected by waves of movement through the endolymph inside the ampullae, utricle and saccule
movement is detected and nerves fire in response. the nerve impulses pass to the vestibular part of cranial nerve 8 which then passes to the brain for interpretation
what are otoloiths?
tiny piece of bone that sit on the receptor cells and move in response to the movement of endolymph
where does the vestibulocochlear nerve run from / to?
from the inner ear to the brain
explain the arterial supply to the inner ear
there are several vessels that supply the internal ear structures mainly from the auditory artery
