Middle Ear

Question 1

Label the middle ear diagram (14)

Answer 1

Question 2

Describe the Eustachian tube

Answer 2

36mm long
Mucous membrane
Tensor palatine muscle
Tiny cilia
1/3 cartilage 2/3 bone
Isthmus narrowest part

Question 3

What is the function of the Eustachian tube?

Answer 3

To drain mucous from middle ear to throat
To equalise air pressure between throat and middle ear

Question 4

What is the physiology of the middle ear?

Answer 4

T - transducer
C - conduction
A - amplifier
P - protection

Question 5

Describe the middle ear transducer

Answer 5

Converts acoustic energy to mechanical energy

Question 6

Describe middle ear conduction

Answer 6

Conducts sound from outer ear to the inner ear

Question 7

Describe amplification in the middle ear (2)

Answer 7

Aerial ratio
TM is 14 times larger than the oval window

Leverage action
Malleus is 1.15 longer than incus = 1.3 pressure increase

Conical shape concentrates signal at umbo

Question 8

Describe protection in the middle ear (reflex’s)

Answer 8

Acoustic reflex
Stapedius muscle contracts to protect inner ear after being exposed to sounds in excess of 70-80dB for a period of time

Non acoustic reflex
Tensor tympani muscle contract when puff of air on cornea. Instant reflex to protect against trauma