Ear Anatomy

Question 1

Blood supply to the auricle (2)

Answer 1

Posterior auricular a.

Superficial temporal a.

Question 2

Innervation of the auricle (4)

Answer 2

Great auricular n.
Auriculotemporal n.
Vagus n.
Facial n.

Question 3

What is the course of the external acoustic meatus?

Answer 3

Extends from concha of auricle to tympanic membrane.

Question 4

What part of the external acoustic meatus is bone vs. cartilage?

Answer 4

Lateral 1/3 is cartilage and slightly S-shaped.

Medial 2/3 is bone.

Question 5

What is otitis externa (AKA Swimmer’s Ear)?

Fisk factors:

Answer 5

infection of external coustic meatus.

Excessive moisture, trauma, hearing aids, prior radiation, etc.

Question 6

What is otitis media?

How does it look on exam?

Answer 6

Infection of middle ear (tympanic cavity).

Tympanic membrane is red and bulging.

Question 7

Tympanostomy tube placement is done to do what?

Answer 7

Drain effusion behind tympanic membrane during OM.

Question 8

Boundaries of the middle ear: roof, floor, lateral, medial, posterior and anterior walls.

Answer 8

Roof: tegmen tempani bone.
Floor: bone
Lateral: tympanic membrane
Medial: promontory, oval window, round window, facial canal.
Posterior: auditus to mastoid antrum, canal for facial n.
Anterior: opening of pharyngotympanic tube and canal for tensor tympani.

Question 9

What does the bone of the floor separate the tympanic cavity from?

Answer 9

IJV

Question 10

What does the anterior wall separate the tympanic cavity from?

Answer 10

ICA and sympathetic plexus

Question 11

What does the tegmen tympani separate the tympanic cavity from?

Answer 11

Middle cranial fossa/temporal lobe

Question 12

Contents of the middle ear (4)

Answer 12

Ossicles (malleus, incus, stapes)
Stapedius and tensor tympani ms.
Chorda tympani n.
Tympanic plexes

Question 13

What does the head of the malleus articulate with?

What does the neck lie against?

Answer 13

Head of Incus.

Lies against flaccid part of tympanic membrane.

Question 14

What is the handle of the malleus embedded in?
Where is the tip of it?
What muscle inserts at the handle?

Answer 14

Embedded in tympanic membrane.
Tip is at the umbo.
Tensor tympani m. inserts at handle.

Question 15

What part of the incus articulates with the stapes?

Answer 15

The long limb of the incus

Question 16

Head of stapes articulates with:

Neck of stapes is insertion site for:

Base (2 limbs) of stapes inserts on:

Answer 16

Incus.

Stapedius m.

Oval window.

Question 17

Tensor tempani m. inserts on:
What does it do?
What is the end action?

Answer 17

Handle of malleus.
Pulls malleus medially –> tenses tympanic membrane.
Prevents damage from loud sound.

Question 18

Stapedius m. inserts on:
What does it do?
What is the end action?

Answer 18

Neck of stapes.
Pulls stapes posteriorly and tilts it base in oval window.
Prevents damage from loud sound.

Question 19

Chorda tempani n. is a branch of what?

What fibers does it have?

What is the function?

Answer 19

Branch of facial n.

PSNS fibers.

Taste to anterior 2/3 of tongue.

Question 20

Tympanic n. is a branch of what?

What does it give rise to?

Answer 20

Glossopharyngeal n.

Tympanic plexus –> lesser petrosal n. (PSNS)

Question 21

3 parts of bony labyrinth

Answer 21

Cochlea
Vestibule
Semicircular canals

Question 22

Within which bone does the bony labyrinth sit?

What is it filled with?

Answer 22

Petrous part of temporal bone.

Perilymph.

Question 23

What is the membranous labyrinth?

Answer 23

A series of communicating sacs and ducts suspended in bony labyrinth.

Question 24

Parts of membranous labyrinth (3)

Answer 24

Vestibular labyrinth: utricle and saccule.
Semicircular ducts.
Cochlear labyrinth: cochlear duct.

Question 25

What fills the membranous labyrinth?

Answer 25

Endolymph