Ear: Middle Ear

Question 1

Site

Answer 1

Ventricle space lying within petrous temporal bone

Question 2

Communications

Answer 2

1. Anterior: nasopharynx via auditory tube
2. Posterior: mastoid antrum via aditus ad antrum

Question 3

Shape

Answer 3

Resembles biconcave lens:
1. Very narrow from side to side (2mm)
2. Longer in its anteroposterior and vertical diameters (15mm)

Question 4

6 walls

Answer 4

1. Roof
2. Floor
3. Anterior wall
4. Posterior wall
5. Medial wall
6. Lateral wall

Question 5

Roof

Answer 5

Tygmen tympani

Question 6

Floor

Answer 6

Thin convex bone plate: separates middle ear from jugular fossa

Question 7

Anterior wall

Answer 7

From above downwards:
1. Canal for tensor tympani
2. Bony part of auditory tube
3. Ascending part carotid canal

Question 8

Posterior wall

Answer 8

1. Aditus ad antrum
2. Pyramid
3. Ventricle part of facial canal behind pyramid

Question 9

Aditus ad antrum

Answer 9

Opening communicating upper part middle ear with mastoid antrum

Question 10

Pyramid

Answer 10

1. Small conical bony projection
2. Contains: Stapedius origin

Question 11

Lateral wall

Answer 11

Tympanic membrane and bone surrounding

Question 12

Medial wall

Answer 12

Thin bone plate separates middle from inner ear
Has the following:
1. Promontory
2. Oval window
3. Round window
4. Horizontal pat of facial canal

Question 13

Promontory

Answer 13

Rounded central bulging with tympanic plexus on it

Question 14

Oval window

Answer 14

Above and behind promontory closed by stapes

Question 15

Round window

Answer 15

Below and behind promontory closed by secondary tympanic membrane

Question 16

Horizontal part of facial canal

Answer 16

Runs Bacardi’s above promontory and oval window

Question 17

Contents

Answer 17

1. Ossicles
2. Muscles
3. Nerves
4. Blood vessels

Question 18

Ossicles

Answer 18

3 ossicles articulating together by synovial joints from lateral to medial:
1. Malleus
2. Incus
3. Stapes

Question 19

Malleus

Answer 19

Fixed to tympanic membrane inner surface

Question 20

Incus

Answer 20

Begin malleus and stapes

Question 21

Stapes

Answer 21

Closes oval window

Question 22

Muscles

Answer 22

Tensor tympani and Stapedius acting together reflexly to damp down high noise by decreasing tympanic membrane vibration and stapes movements

Question 23

Nerves

Answer 23

1. Tympanic plexus
2. Chorda tympani

Question 24

Blood vessels

Answer 24

1. Anterior and posterior tympanic arteries
2. Tympanic branches from ICA
3. Middle meningeal artery
4. Ascending pharyngeal artery

Question 25

Pharyngotympanic (auditory) tube

Answer 25

1. Bony cartilaginous tube (36 mm long) begins from middle ear anterior wall directed downwards, forwards, and medial to end in nasopharynx 1 cm behind inferior concha
2. Normally closed at rest, but opened by combined action of tensor palati and Levator palati during swallowing and yawning