Anatomy and Histology of the Ear Flashcards
What is the ear composed of?
Composed of integument covered elastic carilage
What arteries supply blood to the ear?
Posterior auricular and superficial temporal
What are the nerves that innervate the ear?
Greater auricular nerve and auriculotemporal nerve
What is the epithelium of the inside layer of the tympanic membrane?
Simple cuboidal
What is the epithelium of the outside layer of the tympanic membrane?
Stratified squamous
What nerve innervates the tympanic membrane?
External surface - auriculotemporal nerve
Inner surface - small branch of the V3 and by small auricular branch of the vagus nerve
Where is the middle ear (tympanic cavity) located?
Petrous portion of the temporal bone/
What are the two parts of the inner ear?
Tympanic cavity proper and epitympanic recess
What is another name for eustachian tube?
Pharyngotympanic tube
What is the pharyngotympanic tube?
Canal that connects the tympanic cavity with nasopharynx. It functions to equalize pressure.
What opens the pharyngotympanic tube?
Levator veli palatine, tensor veli palatine, salpingoharyngeus muscles
Where do the auditory ossicles connect?
The tympanic membrane to oval window of the cochlea.
Where does the tensor tympani muscle insert?
Handle of malleolus
What nerve innervates the tensor tympani muscle?
CN V
What is the function of the tensor tympani muscle?
Pulls on the handle to tense the membrane and reduce amplitude.
Where does the stapedius muscle insert?
Exits a small pinhole size foramen and inserts on the stapes.
What innervates the stapedius?
Facial nerve
What is the action of the stapedius muscle?
Pulls stapes posteriorly tightening annular ligament attaching it to window; reduces oscillatory range and prevents excessive movement of stapes.
What is mastoiditis?
Infection of the mastoid cells.
What is perilymph similar to?
CSF
Where does the perilymph drain and how does it get there?
Drains into the subarachnoid space through the perilymph duct.
What electrolytes are different in the endolymph?
High in K+ and low in Na+
Where does the endolymph drain and how does it get there?
Drain via the endolymph duct into venous sinuses of the dura mater.
What are in the cochlear duct of the inner ear?
Sterocilia
What is the “true cilia” that is located next to the tallest stereocilia?
Kinocilium
What do the stereocilia contain?
Mechanoelectrically-gated ion channels
What happens to the stereocilia whenever these ion channels are opened or closed?
They moved towards the kinocilium if the channels are open, they move away if the gates are closed.
What type of nerves are hair cells innervated by?
Efferent and afferent nerves
What three sections make up the cochlear duct?
Scala media, scala vestibuli, and scala tympani
Where is the organ of corti?
On the floor of the scala media resting on the basilar membrane
Where is the outer spiral lamina?
It is the inner spiraling bony shelf serving as support for tectorial membrane and spiral ganglia.
What is the organ of corti composed of?
Hair cells, inner and outer phalangeal cells, and pillar cells
What do sound cause in the organ of corti?
The basilar membrane to vibrate causing deflection of stereocilia attached to tectorial membrane, opening K+ channels in hair cells
What is the path of sound waves?
Sound waves enter ear and cause the tympanic membrane to vibrate
TM vibration moves auditory ossicles
The stapes at the oval window generates pressure waves in the perilymph within the scala vestibuli
Pressure waves cause the vestibular membrane to move, resulting in pressure wave formation in the endolymph within the cochlear duct and displacement of a specific region of the basilar membrane. Hair cells in the organ of Corti are distorted, initiating a nerve signal in the cochlear branch of CN VIII
Remaining pressure waves are transferred to the scala tympani and exit the inner ear via the round window
What parts of the ear are effected during conductive hearing loss?
Outer and middle ear
What parts of the ear are effected during sensorineural hearing loss?
Inner ear or auditory nerve
What parts are effected during central hearing loss?
CNS
What are the purpose of the utricle and saccule?
Serve as sensors for gravity and linear acceleration
What do both the utricle and saccule contain?
A macula
What do the macula contain?
A cluster of hair cells with an otolithic membrane
An otolithic membrane that is covered with calcium carbonate/protein crystals called otoconia
What are two diseases of the membranous labyrinth?
Meniere’s syndrome and viral labyrinthitis
What is Meniere’s syndrome?
Sx include: dizziness, vertigo, tinnitus, and fluctuating hearing loss
Associated with increase endolymph volume leading to abnormal signaling
Cause is unclear
Mild cases are treated with medication
Severe cases require surgical ablation
What is viral labrynthitis?
Similar to the Meniere’s syndrome but the sx usually resolve within a week
