16.5.4 The Ear

Question 1

What is the function of the external ear?

Answer 1

Amplification + source preference

Question 2

Label the external ear.

Answer 2

Question 3

What nerves innervate the external auditory meatus and tympanic membrane?

[IMPORTANT]

Answer 3

• Trigeminal (V)
• Vagus (X)
• Facial (VII) -> Contributes to tympanic membrane

Question 4

What is the function of the middle ear?

Answer 4

Amplification + impedance matching (managing air-fluid transition)

Question 5

What are the muscles found in the middle ear? How are they innervated and what is their function?

Answer 5

2 Muscles → protection from loud, sustained noises.
tensor tympani - innervated by cranial nerve V,
Stapedius - innervated by cranial nerve VII.
Smallest skeletal muscle

Question 6

What is the middle ear?

Answer 6

It is an air-filled cavity between the ear drum and cochlea. It contains the auditory ossicles.

Question 7

Describe the auditory ossicles.

Answer 7

• Malleus -> Largest of the ossicles and is attached to the tympanic membrane at its handle.
• Incus -> Shaped rather like a pre-molar tooth and has a long limb terminating at the stapes.
• Stapes -> Has two limbs and a base which connects to the oval window (i.e. the inner ear).

Question 8

What is hyperacusis?

Answer 8

Hyperacusis → flaccid paralysis of either muscle (e.g. Bell’s palsy (CNVII)) Intolerance to loud sounds (painful).

Question 9

What is otitis media?

Answer 9

• An infection of the middle ear that causes inflammation and a build-up of fluid behind the eardrum.
• If the fluid does not clear eventually, it may have to be drained.

Question 10

What tube is connected to the middle ear and what is its function?

Answer 10

Pharyngotympanic tube (Eustachian tube) -> Connects the ear to the nasopharynx for pressure equalisation

Question 11

What are the two openings between the middle and inner ear? What is the function of each?

Answer 11

• Oval window -> Membrane made to vibrate by the stapes
• Round window -> Membrane vibrates with opposite phase to the oval window, so that the cochlear fluid can move

Question 12

Where is the inner ear located?

Answer 12

In the petrous portion of the temporal bone
internal acoustic meatus

Question 13

1

Answer 13

Organ of corti

Question 14

3

Answer 14

Modiolus

Question 15

4

Answer 15

Stapes bone

Question 16

5

Answer 16

Stapedius muscle

Question 17

Answer 17

Pinna

Question 18

Answer 18

Tragus

Question 19

Answer 19

External acoustic meatus

Question 20

Answer 20

Tympanic membrane

Question 21

Answer 21

Malleus

Question 22

Answer 22

Malleus

Question 23

Answer 23

Stapes

Question 24

Answer 24

Incus

Question 25

Answer 25

Cochlea

Question 26

Saccule

Answer 26

Otolith stimulated by vertical movement and acceleration

Question 27

Utricle

Answer 27

Otolith stimulated by horizontal movement and acceleration

Question 28

Semi-circular canals

Answer 28

3 ducts used to detect rotational movement of the head

Question 29

What makes up the inner ear?

Answer 29

Cochlea, cochlea nerve, spiral ganglion.