Session 7- Functional Anatomy and Disorders of the Ear Flashcards
what components is the temporal bone made up of
squamous part
petromastoid part
tympanic plate
styloid process
where are the middle and inner ear located
petrous part of temporal bone
what is the external ear made up of
pinna
external auditory meatus
skin lined
what is the middle ear made up of
air filled cavity
ossicles
what is the middle ear lined with
resp epithelium
what is the inner ear made up of
cochlea
semicircular canals
what fills the middle and inner cavity
middle- air
inner - fluid
what carries general sensation from ear implications for referred pain from the middle and external ear
C2 C3
Vagus
Trigeminal
Glossopharyngeal
non-otological causes of otalgia
TMJ dysfunction
diseases of oropharynx
disease of larynx and pharynx
function of external ear
collects, transmits and focuses sound waves onto the tympanic membrane
what is a pinna haemotoma
accumulation of blood between cartilage and its overlying perichondrium
how do you get a pinna haemotoma
trauma
subperichondrial haemotoma reduces blood supply to cartilage and causes pressure necrosis of tissue
what can an untreated pinna haematoma lead to
cauliflower deformity
fibrosis-> new asymmetrical carilage
how long is the external auditory meatus
2.5cm
what lines the external acoustic meatus
keratinising stratified squamous epithelium
hair, sebacous glands and ceruminous glands line cartilage except on the bony part
how does the external acoustic meatus self clean
desquamation and skin migration laterally off tympanic membrane out of canal
otitis externa
inflammation of external ear
what is malignant otitis externa
rare serious life threatening
how does otitis media affect the tympanic membrane
buldging
how does otitis media with effusion affect the tympanic membrane
retracted and evidence of fluid in middle ear
how does a cholesteatoma form
retraction of pars flaccida |(TM) forms a sac/ pocket
- traps stratified squamous epithelium and keratin
- proliferates forming cholesteatoma
Usually secondary to chronic eustachian tube dysfunction
what causes a cholesteoma
chronic eustachian tube dysfunction
dangers of a progressing cholesteatoma
enzymatic bone destruction
function of ossicles
amplify and relay vibrations from the TM to the oval window of the cochlea
-transmitting vibration to waves in a fluid medium
what tampers ossicle movement
tensor tympani and stapedius
-contract if excessive vibration due to loud noise
what is otosclerosis
ossicles fused at articulations due to abnormal bone growth particular between base plate of stapes and oval window
function of pharyngotympanic tube
equilibrates pressure of middle ear with atmospheric pressure
allows for ventilation of and drainage of mucous from the middle ear
what causes otitis media with effusion
Eustachian tube dysfunction
- decreases motility of TM and ossicles -> affecting hearing
- the increase in pressure in outer ear drains fluid and tympanic membrane into middle ear
consequences of otitis media with effusion
may persist and/or impede speech and lamguage development/ school performance
how do you treat otitis media with effusion
require grommets - tympanostomy tube
acts to maintain equillibration of pressures
acute otitis media
acute middle ear infection
signs and symptoms of acute otitis media
otalgia
red +/- bulging TM and loss of normal landmarks
temperature
bacterial causes of acute otitis media
streptococcus pneumoniae
Haemophilus influenzae
how does the pharyngotympanic tube differ in infants and what are the consequences of this
shorter and more horizontal
- easier passage for infection from the nasopharynx to the middle ear
- tube can block more easily compromising ventiation and drainage of middle ear increasing risk of middle ear infection and glue ear
complications of acute otitis media
tympanic membrane perforation
facial nerve involvement
rare and life threatening
- mastoiditis
- meningitis
- sigmoid sinus thrombosis
- brain abcess
mastoiditis
middle ear cavity communicates via mastoid antrum with mastoid air cells
provides a potential route for infections to spread into mastoid bonw
how does the cochlea alow heating
fluid movement at the footplate of the stapes leads to a wave of movement of fluid within the cochlea coverted to action potentials which are percieved as sound
how is the vestibular apparatus involed in balance and sense
fluid movement converted into action potentials -> percievd as position sense and balance
what is the cochlea
fluid-filled tube with speacialised hair cells that generate action potentials when moved
how do we hear
auricle and external auditory meatus focuses and funnels sound waves towards tympanic membrane which vibrates
vibration of the ossicles sets up vibrations in cochlear fluid
sensed by stereocilia in the cochlear duct
movement of the stereocilia in organ of corti trigger action potentials in cochlear part of CN VIII
primary auditory cortex
presbycussis
- sensorineural hearing loss associated with old age
- bilateral and graudal
benign paroxysmal positional vertigo
vertigo only
short lived episodes triggered by movement of head
Meniere’s disease
vertigo, hearing loss and tinnitus
hearing loss over time
symptoms longer lasting
acute labrynthitis or acute vestibular neuronitis
history of URT infections
AL= involvement of all inner ear structures, associated with hearing loss/ tinnitus and vertigo
AVN= usually no hearing disturbances or tinnitus
-sudden onset of vomiting and severe vertigo
conductive hearing loss
pathology involving the external and middle ear
- wax
- otitis media (with effusion)
- otosclerosis
sensorineural hearing loss
pathology involving the inner ear structures
- presbycusis
- noise related hearing loss
- meniere’s disease
- otoxic medications
- acoustic neuroma
what is the most likely causative agent in ototis externa
pseudomanas aerugenosa
how does otitis externa present
otalgia
discharge
itching
inflamed narrow ear canal
which nerves carry general somatic sensation from the external ear
c2
mandibular division of trigeminal
vagus
facial
