Anatomy and Histology of the Ear

Question 1

What is the ear composed of?

Answer 1

Composed of integument covered elastic carilage

Question 2

What arteries supply blood to the ear?

Answer 2

Posterior auricular and superficial temporal

Question 3

What are the nerves that innervate the ear?

Answer 3

Greater auricular nerve and auriculotemporal nerve

Question 4

What is the epithelium of the inside layer of the tympanic membrane?

Answer 4

Simple cuboidal

Question 5

What is the epithelium of the outside layer of the tympanic membrane?

Answer 5

Stratified squamous

Question 6

What nerve innervates the tympanic membrane?

Answer 6

External surface - auriculotemporal nerve

Inner surface - small branch of the V3 and by small auricular branch of the vagus nerve

Question 7

Where is the middle ear (tympanic cavity) located?

Answer 7

Petrous portion of the temporal bone/

Question 8

What are the two parts of the inner ear?

Answer 8

Tympanic cavity proper and epitympanic recess

Question 9

What is another name for eustachian tube?

Answer 9

Pharyngotympanic tube

Question 10

What is the pharyngotympanic tube?

Answer 10

Canal that connects the tympanic cavity with nasopharynx. It functions to equalize pressure.

Question 11

What opens the pharyngotympanic tube?

Answer 11

Levator veli palatine, tensor veli palatine, salpingoharyngeus muscles

Question 12

Where do the auditory ossicles connect?

Answer 12

The tympanic membrane to oval window of the cochlea.

Question 13

Where does the tensor tympani muscle insert?

Answer 13

Handle of malleolus

Question 14

What nerve innervates the tensor tympani muscle?

Answer 14

CN V

Question 15

What is the function of the tensor tympani muscle?

Answer 15

Pulls on the handle to tense the membrane and reduce amplitude.

Question 16

Where does the stapedius muscle insert?

Answer 16

Exits a small pinhole size foramen and inserts on the stapes.

Question 17

What innervates the stapedius?

Answer 17

Facial nerve

Question 18

What is the action of the stapedius muscle?

Answer 18

Pulls stapes posteriorly tightening annular ligament attaching it to window; reduces oscillatory range and prevents excessive movement of stapes.

Question 19

What is mastoiditis?

Answer 19

Infection of the mastoid cells.

Question 20

What is perilymph similar to?

Answer 20

CSF

Question 21

Where does the perilymph drain and how does it get there?

Answer 21

Drains into the subarachnoid space through the perilymph duct.

Question 22

What electrolytes are different in the endolymph?

Answer 22

High in K+ and low in Na+

Question 23

Where does the endolymph drain and how does it get there?

Answer 23

Drain via the endolymph duct into venous sinuses of the dura mater.

Question 24

What are in the cochlear duct of the inner ear?

Answer 24

Sterocilia

Question 25

What is the “true cilia” that is located next to the tallest stereocilia?

Answer 25

Kinocilium

Question 26

What do the stereocilia contain?

Answer 26

Mechanoelectrically-gated ion channels

Question 27

What happens to the stereocilia whenever these ion channels are opened or closed?

Answer 27

They moved towards the kinocilium if the channels are open, they move away if the gates are closed.

Question 28

What type of nerves are hair cells innervated by?

Answer 28

Efferent and afferent nerves

Question 29

What three sections make up the cochlear duct?

Answer 29

Scala media, scala vestibuli, and scala tympani

Question 30

Where is the organ of corti?

Answer 30

On the floor of the scala media resting on the basilar membrane

Question 31

Where is the outer spiral lamina?

Answer 31

It is the inner spiraling bony shelf serving as support for tectorial membrane and spiral ganglia.

Question 32

What is the organ of corti composed of?

Answer 32

Hair cells, inner and outer phalangeal cells, and pillar cells

Question 33

What do sound cause in the organ of corti?

Answer 33

The basilar membrane to vibrate causing deflection of stereocilia attached to tectorial membrane, opening K+ channels in hair cells

Question 34

What is the path of sound waves?

Answer 34

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

Question 35

What parts of the ear are effected during conductive hearing loss?

Answer 35

Outer and middle ear

Question 36

What parts of the ear are effected during sensorineural hearing loss?

Answer 36

Inner ear or auditory nerve

Question 37

What parts are effected during central hearing loss?

Answer 37

CNS

Question 38

What are the purpose of the utricle and saccule?

Answer 38

Serve as sensors for gravity and linear acceleration

Question 39

What do both the utricle and saccule contain?

Answer 39

A macula

Question 40

What do the macula contain?

Answer 40

A cluster of hair cells with an otolithic membrane

An otolithic membrane that is covered with calcium carbonate/protein crystals called otoconia

Question 41

What are two diseases of the membranous labyrinth?

Answer 41

Meniere’s syndrome and viral labyrinthitis

Question 42

What is Meniere’s syndrome?

Answer 42

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

Question 43

What is viral labrynthitis?

Answer 43

Similar to the Meniere’s syndrome but the sx usually resolve within a week