ENT part 2 Flashcards
Tympanic membrane innervation
Facial nerve
Auriculotemporal nerve
Auricular branch of the vagus nerve
What are the smallest bones in the body?
The ossicles
MIS
Malleus –> incus –> stapes –> oval window
Why do we need mechanical leverage in the middle ear?
to hear things better
we are transmitting from an air-filled area to a fluid-filled area
Which two muscles act on the ossicles?
the tensor tympani (attaches to malleus and reduces vibrations of TM)
the stapedius muscle (attaches to stapes and reduces vibrations on the oval window)
Innervation of the tensor tympani muscle
mandibular nerve
Innervation of the stapedius muscle
facial nerve
Eustachian tube goes from ____ to ____
tympanic cavity to nasopharynx
opens near the adenoids
Major functions of the eustachian tube
regulate pressure between middle and external ear
drain middle ear secretions
Blood supply for the cochlea and vestibular complex
AIAC
anterior inferior cerebellar artery
Innervation of the vestibular complex and cochlea
vestibulocochlear nerve (CN8)
What is the primary organ of hearing
cochlea
Functions of cochlea
receives sounds from the acoustic chain through the oval window
converts mechanical impulses to electrical impulses
Major structures of the cochlea
Scala tympani, scala media (cochlear duct), scala vestibuli, helicotrema, organ of Corti
Sound impulse pathway through cochlea
oval window –> scala vestibuli –> helicotrema –> scala tympanic –> round window
Helicotrema
The point at which the scala vestibuli turns in the scala tympani
Vestibular membrane/Reissner’s membrane
separates scala vestibuli & scala media (cochlear duct)
Basilar membrane
separates scala tympani and scala media (cochlear duct)
differing levels of flexibility which equates to different frequencies in hearing
Flexion of the basilar membrane pushes the (spiral) organ of Corti into the tectorial membrane which causes hearing (hair cells contact the tectorial membrane)
Scala vestibuli and scala tympani are both filled with
perilymph (low in potassium)
scala media is filled with
endolymph (high in potassium)
What produces the high potassium endolymph?
the stria vascularis
It also recharges our endolymph after signal sent down cochlear nerve
Major structures of the vestibular complex
saccule
utricle
semicircular canals
Saccule
sac-like structure (easy enough!)
functions: stationary balance and linear vertical movement (think getting on an elevator)
Utricle
larger sac-like structure attached to semicircular canals
sensitive to linear acceleration (think cup of coffee, motion based balance)
Semicircular canals
hoop-shaped canals with associated enlargements at the ends (ampulla)
found in multiple planes
major function is sensing rotation/position of head
Utricle and saccule have ____ at the bottom, while semicircular canals have ____ at the bottom
utricle and saccule have sensory membranes for gravity
semicircular canals have ampulla for fluid (based on flow rather than gravity)
The nasal cavity is separated into two regions by the
nasal septum (thin bony/cartilaginous)
Major functions of nasal cavity
breathing
olfaction
warming/humidifying/filtering
immune functions
blood supply to nasal cavity
varied, with all supply coming from internal and external carotid arteries
angular artery and lateral nasal artery (from the facial artery)
dorsal nasal artery (from ophthalmic artery)
Innervation of nasal cavity
olfactory nerve (cranial nerve 1)
trigeminal nerve
facial nerve
Nasal cartilage
Alar (paired)
Lateral (paired)
Septal
Venous drainage of the nose
Anastomosis with the cavernous sinus of the brain via the ophthalmic veins
So watch for brain infections — this is a very rare complication though
