Ear Flashcards
what bone in the skull is the ear associated with
petrous temporal bone
what are the 3 parts of the ear?
external, middle and internal
what do the middle and external ear do
transfer sound to the internal ear
what separates the external and middle ear
tympanic membrane
what does the pharyngotympanic tube join
middle ear to nasopharynx
what is the auricle made of
elastic cartilage
what is the main function of the auricle
support the ear, catch and funnel sound to external acoustic meatus
what are the main parts of the auricle
helix, lobule, tragus, concha
what is the sensory innervation of the auricle
great auricular (for medial surface, back of ear) and auriculotemporal (for anterior ear, tragus)
what is the external acoustic meatus made of
cartilage and bone
what epithelium is in the external acoustic meatus and what does it contain
stratified squamous
hair follicles, glands, ceruminous glands secreting ear war, blood vessels, nerves
how is the tympanic membrane held within the temporal bone
by a fibrocartilaginous ring
what is the tympanic membrane covered in
skin externally and mucous membranes internally
why does the tympanic membrane move
in response to air vibrations passed to it through the EAM
once the tympanic membrane moves, where does this movement go to
transmitted by ossicles through middle ear and to the internal ear
how can the tympanic membrane be examined
by an otoscope
what does the cone of light mean when it is seen on an otoscope
that the tympanic membrane is healthy and there is no fluid accumulation
what is the middle ear called
tympanic cavity
what does the middle ear contain
ossicles and muscles, pharyngotympanic tube
what are the ossicles
malleus, incus and stapes
what are the 2 muscles in the middle ear
tensor tympani and stapedius
what attaches to the tympanic membrane
handle of malleus
what attaches to the oval window
base of stapes
what do the ossicles do with sound
increase the force and decrease the amplitude
why do the ossicles increase force and decrease amplitude of sound
because the inner ear is fluid filled and it needs to change the sound to match the fluid waves
what do the small muscles in the middle ear do
dampen/resist movement of ossicles and have protective function over the ear and tympanic membrane
where does the tensor tympani insert into
handle of malleus
what does the tensor tympani do
pulls handle of malleus medially which tenses the tympanic membrane reducing the amplitude of oscillations (prevent damage)
what does the stapedius do
pulls stapes posteriorly reducing range of oscillations and excessive movement of stapes
what is the stapedius innervated by
nerve to stapedius
what is the tensor tympani innervated by
mandibular division of trigeminal nerve
what is the pharyngotympanic tube made of
initially bone and then cartilages
what is the function of the pharyngotympanic tube
pressure equalisation between middle ear and atmospheric pressure and replenishes air of middle ear
what can occur as a result of the pharyngotympanic tube
middle ear infections
what nerves enter the internal acoustic meatus
facial nerve and vestibulocochlear
what is the course of the facial nerve
internal acoustic meatus - facial canal (greater petrosal given off) - chorda tympani and nerve to stapedius given off
what blood vessels run close to the middle ear
ICA and IJV
the roof of the ear is very thin between middle cranial fossa and ear, what does this mean
infection spread to cranial cavity
severe infection erodes the bone towards vascular and can affect ICA and IJV meaning systemic spread of infection
what are middle ear infections called
otitis media
what can chronic infection in the middle ear cause
damage to the ossicles - conductive deafness
infection spread to mastoid cells (mastoiditis)
how is mastoiditis treated and what do you need to be aware of
antibiotics but mainly surgery so be aware of facial nerve
how is the ear connected to the mastoid
through mastoid antrum
what is conductive hearing loss
condition of sound production through ossicles causing deafness
what is otitis media with effusion
build up of fluid behind tympanic membrane which restricts movement of ossicles
how do you fix otitis media
grommets
what is contained in the bony labyrinth of the inner ear
vestibule, cochlea, semi-circular canals
what fluid does the bony labyrinth contain
perilymph
what is the structure of the inner ear
bony labyrinth containing membranous labyrinth
what fluid does the membranous labyrinth of inner ear contain
endolymph
what does endolymph do
stimulate organs for balance and hearing
what bone contains the inner ear
otic capsule
what is the function of the cochlea
hearing
what is the function of the vestibule
balance
what is the function of the semi-circular canals
balance (communicate with vestibule)
what signal does the vestibulocochlear nerve convey
motion and hearing
where does CNVIII divide
lateral end of internal acoustic meatus
what are the 2 divisions of CNVIII
vestibular and cochlear
what does the cochlear nerve supply
cochlea
what does the vestibular nerve supply
semi-circular canals, saccule and utricle (vestibule)
what can damage to the cochlear nerve result in
hearing loss (either neural or conductive)
what does the cochlear nerve do
receptor of auditory stimuli
what does the vestibular nerve do
balance and equilibrium
what can damage to the vestibular nerve do
ataxia, vertigo and nausea
