Pharyngeal Apparatus: Pouches

Question 1

Pharyngeal pouches

Answer 1

Each has dorsal and ventral wings
4 pouches

Question 2

1st pouch

Answer 2

Forms tubotympanic recess which gives rise to:
1. Eustachian tube
2. Middle ear cavity
3. Mastoid antrum
4. Ear drum inner layer

Question 3

2nd pouch

Answer 3

1. Endodermal lining of 2nd pouch proliferates and forms buds which are are secondarily invaded by mesodermal tissue, forming palatine tonsil
2. At 3rd and 5th months, palatine tonsils become invaded by lymphatic tissue
3. Pouch remaining persists as tonsillar fossa

Question 4

3rd pouch

Answer 4

1. Forms inferior parathyroid gland (dorsal wing) and thymus gland (ventral wing)
2. Both gland primordial lose their connection with pharyngeal wall to reach their final destination

Question 5

4th pouch

Answer 5

Forms superior parathyroid gland (dorsal wing) and ultimo-branchial body (ventral wing) which gives rise to parafollicular (C) cells of thyroid