Ear & Auditory Tube

Question 1

Which nerves innervate the ear?

Answer 1

The vagus & auriculotemporal nerve (branch of the mandibular division of trigeminal nerve).

Question 2

In which quadrant of the tympanic membrane is the cone of light?

Answer 2

Antero-inferior.

Question 3

Why is displacement of the cone of light a good indicator of a problem in the middle ear?

Answer 3

Inflammation/a build up of pressure/etc. will change the concavity of the tympanic membrane, so you won’t see that cone of light in the same quadrant.

Question 4

What is the most important function of the auditory tube?

Answer 4

It allows equalisation of pressure between the middle ear & the atmosphere via the nasopharynx.

Question 5

What kind of joints are the joints between the ossicles of the ear?

Answer 5

Synovial joints.

Question 6

What is the difference between adult and infant auditory tubes, and why can this be problematic?

Answer 6

Babies have a very horizontal auditory tube, so bacteria can migrate across into the middle ear much more easily and is more difficult to drain. Thus, middle ear infections are much more common in babies.

Question 7

Which nerve innervates the stapedius?

Answer 7

The facial nerve.

Question 8

Which nerve innervates the tensor tympani?

Answer 8

The trigeminal nerve.

Question 9

How do stapedius and tensor tympani act to protect us from loud noises?

Answer 9

They undergo reflex contraction in response to a very loud noise, pulling the ossicles tight and stopping them from vibrating with as much amplitude, dampening the sound presented to the inner ear.

Question 10

Sometimes, if there is water on the tympanic membrane, you can hear a throbbing. What causes this?

Answer 10

The throbbing is a result of the mechanical energy from the pulsing of the carotid artery being pushed through that fluid interface and impacting on the ossicles.

Question 11

What is the name of the fluid inside the bony labyrinth?

Answer 11

Perilymph.

Question 12

What is the name of the fluid-filled sac within the perilymph?

Answer 12

The membranous labyrinth.

Question 13

What is the name of the fluid inside the membranous labyrinth?

Answer 13

Endolymph.

Question 14

In which part of the temporal bone is the bony labyrinth embedded?

Answer 14

The petrous part.

Question 15

At which part of the cochlea are high frequency sounds translated?

Answer 15

The base.

Question 16

At which part of the cochlea are low frequency sounds translated?

Answer 16

The apex.

Question 17

How does movement of the endolymph tell our brain that our head is moving?

Answer 17

When our head moves, the endolymph lags behind, because it is thick & viscous. It moves in the opposite direction to our head movement. As it does so, it moves past the sensory receptors in the ampulla, deflecting the gelatinous cap (cupula) and activating the hair cells, telling our brain that there is movement.