Lecture 20 Content Flashcards
Describe the Auditory canal?
- Skin of canal innervated by CN X (vagus)
- tympanic membrane (ear drum) = 2 layers
- external auditory canal = Cartilage + meatus (bone)
- TMD = TMJ dysfunction (shared nerves)
What makes up the middle ear?
outer ear/ear drum + pharynx + mastoid sinus + inner ear
What does the petrosal portion of the ear do?
Massive
- protect inner and middle ear
How is the ear drum placed in the auditory canal?
it is stretched across
What is on the lateral border of the middle ear?
tympanic membrane collects sound waves
What is on the medial border of the middle ear?
bony wall separating middle ear from inner ear
What is on the superior border of the middle ear?
petrous portion of the temporal bone
What is on the posterior border of the middle ear?
pneumatized (mastoid antrum)
What is on the anterior border of the middle ear?
opening of the auditory (eustachian tube)
what are the 3 auditory ossicles?
malleus, incus, stapes
What do the auditory ossicles do?
they carry vbrations from ear drum > oval window
what muscle is connecting the malleus and what attaches to the stapes?
malleus - tensor tympani muscle
stapes - stapedius muscle
What does the tympanic membrane do in hearing?
(tympanic reflex)
- tensor tympani places tension across eardrum
- stapedius “locks down the ossicular chain
= dampens vibration from excessively loud sounds
Describe the Auditory tube? or Eustachian tube?
Connects middle - ear to pharynx
- tube is supported by muscle and cartilage
- EQUALIZES pressure across tympanic membrane
What can happen when fluid builds up in the auditory tube?
- will become inflamed and will swell shut
- fluid can be trapped in middle ear
- fluid build up, and pressure = pain
- threatens the ear drum and sense of hearing/ balance
What can happen when fluid builds up in the auditory tube?
- will become inflamed and will swell shut
- fluid can be trapped in middle ear
- fluid build up, and pressure = pain
- threatens the ear drum and sense of hearing/ balance
What is a Myringotomy?
- drainage tube
- insertion of tube tat perfortrates the ear drum
- release fluid / pressure in the middle ear
- if fluid is not released infection can spread - - on dif. notecard
What are the diffrent infections that can happen if you don’e have a myringotomy done?
mastoiditis - infection of mastoid air cells
otitis media - infection of middle ear
labyrinthitis - infection of inner ear
What is Osseous Labrynth?
- boney canals in petrous portion of the temporal bone
- membranous labyrinths is housed within the boney labyrinth
Where is the membranous labyrinth?
it is the hollow tubes / chambers within the osseous labyrinth
where is the endolymph
- fills each canal/chamber
Where is the perilymph?
space between osseous and membranous labyrinths
What does the hair cells do in hearing?
- functional unit of hearing and equilibrium
- hair cells located within MEMBRANOUS LABYRINTH
- vibration/movement of stereocillia = signal VIII
(nothing to do with hair)
What are the names of the semicircular canals? what is inside?
lateral anterior posterior
- filled with endolymph
What is the swelling at each of semicircular base called?
ampulla
How are the hair cells aligned in the Ampullae?
- hair cells aligned on a ridge = crista
- Tips of hair cells are embedded in gel = capula
How are the Cupulae are based on the movement?
are distorted by endolymph movement
= sensitive to changes in position (rotation)
- fluid doesn’t move the head it is the fluid trying to stay level
What makes up the Vestibular complex?
- utricle and saccule: each has a macula
- maculae equipped w/ hair cells covered by thick gel
- gel ornmented w/ calcium carbonate crystals
- Otoliths provide mass across top of hair cells
- Diffrential movement of gel and head = signal
= gravity, tilt, and linear acceleration
What is vertigo? related to receptor overload
- steady movement induced endolymph to flow
- flow can be interrupted by abrupt stop/change
- dizziness and nausea
What is vertigo related to mismatch of audio/visual information?
- vestibular apparatus senses movement
- visual system stays stationary
- vestbular nuclei in the brain stem are confused]
- dizziness and nausea
explain how vestibular nystagmus works?
- steady movement induces endolymph to flow
- if movement continues
- endolymph stops flowing)
- eyes get accustom to the tracking of movements
- eye/vestibular systems are interconnected (corp. quad)
- if spinning movement suddenly stops
- endolymph is suddenly re-accelerated
- dizziness and nausea ensures
- eye will race (Nystagmus) in the direction of spin
- continues until the endolymph calms down
describe how you hear high-pitched tones?
high pitched tones = high frequency vibrations
- high frequencies have short wave lengths
- short wave lengths travel short distances (Pin drop)
(Base of BM)
Describe how you hear low pitched tones?
low pitched tones = low frequency vibration
- low frequencies have long wave lengths
- low wave-lengths travel long distance (trunk)
TIP of BM
What in the inner ear is responsible for hearing?
cochlea CN VIII
What is the cochlear duct?
coiled tube resembling snails shell
- part of the membranous labyrint (endolymph)
what is the basal membrane?
floor of cochlear duct
where is the vestibular duct?
oval window to the helicotrema
- filled with perilymph
what is the tympanic duct?
- helicotrema to the round window
- filled with perilymph
what is the helicotrema?
(helical extremity) - tip of cochlea
what duct covers the oval window for the stapes?
vestibular duct
What duct covers the round window?
tympanic duct
what is the organ of cotri?
auditory receptor
- hair cells distributed along basal membrane
- tips of hair cells in contact with tectorial membrane
- distortion of basal membrane/hair cells = signal
- signal > cochlear part of CN VIII
How does sound goes through the ear?
- sound vibrates the ear drum which vibrates ossicles
- stapes oscillates within the oval window
- membrane vibrates the perilymph in vestibular duct
- vibration go around helicotrema into tympanic duct
- pressure causes round window to buldge outwards
what is the place theory?
- each wave-length has a “sweet-spot” along BM
- basilar membrane BM is ribbon-like
- thick/stiff at the base : thin/floppy @helicotrema
- combination of wave-length/location = sound
