Ear and auditory canal anatomy

Question 1

What are the borders of the outer ear?

Answer 1

from the external auditory meatus to the tympanic membrane

Question 2

What is the sensory innervation to the external auditory meatus?

Answer 2

Auriculotemporal nerve (branch of V3-mandibular) supplies the anterior/superior surfaces and the external tympanic membrane. Vagus nerve suplies the posteroinferior parts

Question 3

Where can ear pain refer to and why?

Answer 3

can refer pain to teeth via the inferior alveolar nerve (branch of the mandibular)

Question 4

Looking at the tympanic membrane where is the cone of light usually found? displacement from here can indicate what?

Answer 4

usually in the antero-inferior quadrant -> high pressure in the middle ear can alter the concavity of the membrane and cause displacement

Question 5

What are the boundaries of the middle ear?

Answer 5

tympanic membrane to oval window (in petrous part of temporal bone)

Question 6

What is the epitympanic recess? what is significant about this space?

Answer 6

superior to tympanic membrane within the middle ear- communicates with the mastoid air cells therefore infection can spread and fester in these poorly drained air cells.

Question 7

What is the auditory tube made up of?

Answer 7

1/3rd = bone (closest part to middle ear) 2/3rds cartilage - can change positions using muscles (ie how we ‘pop’ our ears)

Question 8

Why are children more prone to middle ear infections?

Answer 8

auditory/eustachian tube is more horizontal -> easier for bacteria to migrate upwards and harder for it to drain

Question 9

What are gromets?

Answer 9

small devices allowing communication (through the tympanic membrane) between the atmosphere and the middle ear allowing for equalization and drainage

Question 10

What are the ossicles? what are the functions?

Answer 10

small bones within the middle ear that attach to the tympanic membrane (Malleus) and the opening to the inner ear (Oval window - Stapes)

Question 11

Name the 3 ossicles

Answer 11

Stapes, Incus, Malleus

Question 12

What muscles attach to the ossicles? What are their functions?

Answer 12

Tensor Tympani attaches to Malleus, Stapedius attaches to Stapes. Pull on and thus dampen the vibrations to prevent damage to the hearing receptors

Question 13

What nerve innervates Stapedius?

Answer 13

S for Seventh -> facial nerve CNVII

Question 14

What nerve innervates Tensor Tympani?

Answer 14

T for Trigeminal

Question 15

What is the promontory? why is it useful?

Answer 15

bulge seen when looking laterally with TM removed -> good marker for oval and round windows

Question 16

What are the boundaries of the inner ear?

Answer 16

from the oval window to the cavities within the petrous part of the temporal bone

Question 17

Immediately after the oval window is what space? What is its function?

Answer 17

the vestibule -> made up of the Saccule and Utricle. Sensory receptors here are responsible for detecting head position (static equilibrium)

Question 18

What kind of fluid is within the bony labyrinth?

Answer 18

perilymph

Question 19

What fluid is contained within the membranous labyrinth?

Answer 19

endolymph

Question 20

What are the semicircular canals?

Answer 20

Anterior, horizontal and posterior -> each at right angles to the other two

Question 21

What part of the inner ear is involved in dynamic equilibrium?

Answer 21

Ampulla = swellings at the end of each semicircular duct

Question 22

Where in the ear are the receptors for hearing?

Answer 22

Cochlear duct