Middle Ear Flashcards
where is the middle ear?
within the temporal bone
where does the middle ear extend from and to?
from tympanic membrane to the lateral wall of the inner ear
what is the main function of the middle ear?
transmits vibrations from the tympanic membrane to the inner ear via auditory ossicles
what two parts can the middle ear be divided into?
- tympanic cavity
- epitympanic cavity
what does the tympanic cavity contain?
auditory ossicles - malleus, incus and stapes
what are the 3 auditory ossicles? list from largest to smallest
malleus, incus, stapes
what is the role of the auditory ossicles?
transmit sound vibrations through the middle ear
how do the auditory ossicles work?
- sound vibrations causes tympanic membrane to move/oscillate
- causes auditory ossicles to move
how does the malleus attach to the tympanic membrane?
via the handle of malleus
what do the two limbs on the incus attach to?
short limb - posterior wall of middle ear
long limb - joins to stapes
what does the base of the stapes attach to?
oval window of inner ear
describe how the auditory ossicles attach to each other:
- handle of malleus attaches malleus to tympanic membrane
- head of malleus articulates with incus in epitympanic recess
- long limb of incus articulates with stapes
- base of stapes joins the oval window of the inner ear
what cells are located posterior to the epitympanic recess?
mastoid air cells - found in mastoid process of temporal bone
what is the role of the mastoid air cells?
- “buffer system of air”
- release air into tympanic cavity when the pressure is too low
what connects the mastoid antrum (cavity that contains the mastoid air cells) with the middle ear?
aditus to mastoid antrum
what two muscles serve a protective function in the middle ear?
tensor tympani
stapedius
what is the acoustic reflex?
- tensor tympani and stapedius contract in response to loud noise
- inhibits vibrations of auditory ossicles
- reduces transmission of sound to inner ear
where does the tensor tympani originate and attach?
originates from auditory tube
attaches to handle of malleus
how does the tensor tympani pull the handle of malleus what contracting?
pulls it medially
what is tensor tympani innervated by?
tensor tympani nerve - branch of mandibular
where does the stapedius muscle attach?
stapes
what is the stapedius muscle innervated by?
facial nerve
what is the auditory/eustachian tube?
a cartilaginous and bony tube that connects the middle ear to the nasopharynx
what is the role of the auditory tube?
equalises pressure of the middle ear to that of the external auditory meatus
which wall of the nasopharynx does the auditory tube open into?
lateral wall
why do middle ear infections tend to be more common in children than adults?
tube is shorter and straighter in children than in adults
what is the pathology of otitis media with effusion/”glue ear”?
- persistant dysfunction of the auditory tube causes a negative pressure to develop in the middle ear
- draws out transudate from muscose of middle ear
- causes infection
how will the eardrum appear in a pt with otitis media with effusion?
inverted, wiht visible fluid inside the ear
what is mastoiditis?
middle ear infection spreads to mastoid air cells
what is a potentially fatal consequence of mastoiditis?
infection can spread to middle cranial fossa and cause meningitis
Label this diagram showing the mastkid air cells
Label the bones of the middle ear
Label this diagram of the middle ear
Label the muscles of the inner ear
