Mastoid air cells, muscles, Auditory Tube, clinical Flashcards
what is the auditory tube also known as?
eustachian tube
what is the auditory tube?
a cartilaginous and bony tube that connects the middle ear to the nasopharynx
function of the auditory tube?
It acts to equalise the pressure of the middle ear to that of the external auditory meatus
where does the auditory tube extend?
It extends from the anterior wall of the middle ear, in anterior, medioinferior direction
where does the auditory tube open onto?
the lateral wall of the nasopharynx
In joining the two structures (auditory tube and lateral wall of nasopharynx), what does the auditory tube provide a pathway for?
In joining the two structures, it is a pathway by which an upper respiratory infection can spread into the middle ear
where are mastoid air cells located?
posterior to epitympanic recess
what are mastoid air cells?
a collection of air-filled spaces in the mastoid process of the temporal bone
what are the air cells are contained within a cavity called?
the mastoid antrum
how does the mastoid antrum communicates with the middle ear?
via the aditus to mastoid antrum
what do the mastoid air cells act as?
a ‘buffer system‘ of air – releasing air into the tympanic cavity when the pressure is too low
what is middle ear infection?
otitis media
where can middle ear infections spread to?
mastoid air cells
what are mastoid air cells suitable for? (think otitis media)
due to their porous nature, they are a suitable site for pathogenic replication
what can be infected in otitis media?
the mastoid process itself
where can infection spread to if the mastoid process is infected? causing?
middle cranial fossa and into the brain, causing meningitis
if mastoiditis is suspected, what must you do?
the pus must be drained from the air cells
when draining pus from the air cells in mastoiditis, what must one be cautious of?
care must be taken not to damage the nearby facial nerve
how many muscles are there in the middle ear? function?
There are two muscles which serve a protective function in the middle ear
what are the 2 protective muscles of the middle ear?
the tensor tympani and stapedius
how do the tensor tympani and stapedius act in the middle ear?
They contract in response to loud noise, inhibiting the vibrations of the malleus, incus and stapes, and reducing the transmission of sound to the inner ear
what are the actions of tensor tympani and stapedius called?
acoustic reflex
where does the tensor tympani originate from? attach?
the auditory tube and attaches to the handle of malleus, pulling it medially when contracting
what is the tensor tympani innervated by?
a branch of the mandibular nerve
where does the stapedius muscle attach to?
the stapes
what is the stapedius muscle innervated by?
the facial nerve
what is glue ear?
Otitis media with effusion
how does glue ear arise?
It arises from persistent dysfunction of the auditory tube.
what will happen if the auditory tube is unable to equalise middle ear pressure?
a negative pressure develops inside the middle ear
what causes auditory tube to not be able to equalise middle ear pressure?
due to blockage, inflammation, genetic mutation
what does the negative pressure within middle ear from auditory tube unable to equalise middle ear pressure cause?
This negative pressure draws out a transudate from the mucosa of the middle ear, creating an environment suitable for pathogens to replicate and cause infection.
Upon inspection of a patient with otitis media with effusion, how will the eardrum appear?
the eardrum will appear inverted, with fluid visible inside the ear
