H&N 6 Flashcards
Embryological origin of external ear?
auricle- prolif of cells in 1st and 2nd pharyngeal arches
external auditory meatus- 1st pharyngeal cleft
auricle function?*
collects sound
where does the EAM terminate?
at the fibrous tympanic membrane
where does the middle ear lie?
in petrous temporal bone
components of middle ear?
tympanic cavity, lying immediately medial to tympanic membrane
epitympanic recess- space superior to tympanic membrane
how does middle ear communicate with nasopharynx?
connected by Eustachian tube anteriorly
what does middle ear communicate with posteriorly?
mastoid cells in mastoid process of temporal bone
bones of middle ear?
3 auditory ossicles: malleus, incus and stapes, which conduct sound waves to inner part of ear
what are the 2 tympanic muscles stapedius (from 2nd P arch, facial nerve) and tensor tympani (1st P arch, trigeminal nerve, concerned with?
dampening large m.ments of tympanic membrane
2 parts of inner ear?
membranous and bony labyrinths- membranous lies within bony
embry origin of membranous labyrinth?
otic placodes- thickenings of ectoderm
what does bony labyrinth consist of?
cochlea- concerned with sound perception, vestibule and semicircular canals- both involved in balance, suspended in perilymph
composition of membranous labyrinth?
series of communicating sacs and ducts, and contains endolymphs
what happens at base of cochlea?
bony labyrinth communicates with subarachnoid space via cochlear aqueduct
what is the vestibule concerned with?
balance
how do fibres of CNVIII reach inner ear?
pass through internal acoustic meatus on inner aspect of petrous temporal bone
common causes of otalgia?
external otitis and otitis media
4 temporal bone components?
squamous part- TMJ
petromastoid part
tympanic plate
styloid process
what does the external acoustic meatus consists mainly of?
tympanic plate
which part of the temporal bone contains the middle an d inner ears?
petromastoid part
how can middle ear disease cause mastoiditis?
the cavity of the mastoid antrum ( a prolongation of the cavity of the middle ear), is prolonged into the mastoid process by intercommunicating air cells
what does the skin lining the external auditory meatus secrete?
cerumen- modified sebum- affords protection for delicate meatal skin
how is wax formed?
by cerumen and discarded cells of skin
to what is the apex of the eardrum (tympanic membrane) attached?
malleus
how is eustachian tube opened intermittently?
by pull of attached palate muscles when swallowing
why might a middle ear infection cause a lesion of the facial nerve?
nerve lies within the facial canal which is separated from the middle ear cavity by only a very thin bony partition
when may perforation of tympanic membrane occur?
after trauma or infection
why are people advised to take sweets to stop their ears from becoming blocked on a plane?
As during swallowing, the Eustachian tube is opened by the pull of the attached palate muscles, so this helps to keep the tube open and hence prevent blockage
how is an auricular haematoma treated?
blood aspiration
contents of middle ear?
auditory ossicles- malleus, incus, stapes
stapedius and tensor tympani muscles
chorda tympani nerve- branch of facial nerve
tympanic plexus of nerves
innervation of stapedius?
facial nerve