Middle Ear

Question 1

What portion of the Eustachian tube is surrounded by cartilage? Bone?

Answer 1

Bone: superior 1/3
Cartilage: inferior 2/3

Question 2

Which nerve runs next to the middle ear cavity?

Answer 2

-CN VII

Question 3

What is the promontory? What is its function?

Answer 3

• Covering of the basal turn of the cochlea, help form the medial wall of the middle ear cavity
• Protection mechanism for the oval and round windows

Question 4

What vein runs next to the inferior wall of the middle ear cavity? What type of tumor is common
to destroy this wall?

Answer 4

• Jugular vein

- Glomus jugulare tumor

Question 5

The children the Eustachian tube is roughly at what angle? In adults?

Answer 5

• Children: 180 degrees

- Adults: 45 degrees sloping downward

Question 6

What are the names of the ossicles?

Answer 6

• Malleus
• Incus
• Stapes

Question 7

The middle ear bones solves what major problem in the transduction of sound?

Answer 7

-Impedance mismatch

Question 8

What are the three mechanisms that the ossicles improve sound transduction?

Answer 8

• Difference in surface area between TM and stapes footplate
• Buckling motion of the TM
• Lever action between malleus and incus

Question 9

The tympanic membrane moves in what direction?

Answer 9

-Horizontal buckling motion (not piston-like)

Question 10

Which of the ossicles is the weakest and most likely to break?

Answer 10

-Stapes