Ear and guttural pouch

Question 1

What is the space running inside the cartilages of the ear to the tympanic membrane called?

Answer 1

External auditory meatus = ear canal

Question 2

What are the 3 groups of muscles of the external ear, and their functions?

Answer 2

• pre auricular: moves ear forward
• ventral auricular: moves ear ventrally
• post auricular: moves ear caudally and medially

Question 3

Describe the motor nerve supply to the external ear

Answer 3

Rostral and caudal auricular nerve from the facial nerve.

Great auricular nerve from C2.

Question 4

Where is the middle ear located?

Answer 4

A cavity that lies within the temporal bone

Question 5

What lies ventrally and laterally to the middle ear?

Answer 5

Ventrally = tympanic bulla
Laterally = tympanic membrane

Question 6

How is pressure on either side of the tympanic membrane equalised?

Answer 6

Upon swallowing or yawning, the entrance to the auditory tubes (ostia) is forced open and air enters them and then moves into the middle ear cavity where it equalises the pressure on either side

Question 7

What is the guttural pouch?

Answer 7

An air filled diverticulum of the auditory tube only found in equidae

Question 8

How is the guttural pouch divided?

Answer 8

Divided ventrally into medial and lateral compartments by stylohyoid bone (medial is larger 2/3 vs lateral 1/3)

Question 9

How does drainage of the guttural pouch occur?

Answer 9

Through the dorsal ostia - head needs to be down to drain and the ostia are opened during swallowing

Question 10

What is the main landmark for a lateral surgical approach to the guttural pouch?

Answer 10

Viborg’s triangle

Question 11

Define the following terms which link to diseases of the guttural pouch:

1. Tympany
2. Empyema
3. Mycosis

Answer 11

• Air distention
• Bacterial infection
• Fungal infection