Brachial pouch derivatives

Question 1

1st pouch

Answer 1

Middle ear cavity,
eustachian tube
mastoid air cell

Contributes to endoderm-lined structures of ear

Question 2

2nd pouch

Answer 2

Epithelial lining of palatine tonsil

Question 3

3rd pouch

Answer 3

Dorsal wings- inferior parathyroid
Ventral wings- thymus

3rd pouch contributes to structures (thymus, inferior parathyroid)

3rd pouch structures end below the 4th pouch derivatives

Question 4

4th pouch

Answer 4

Dorsal wing-superior parathyroid

Question 5

Mneumonics

Answer 5

Ear, tonsil, bottom-to-top:
1 (ear)
2 (tonsils)
3 dorsal (bottom for inferior parathyroid)
4 (top=superior parathyroid)

Question 6

DiGeorge Syndrome

Answer 6

3rd and 4th pouch deficient
T cell deficiency (thymic aplasia) and
hypocalcemia (failure of parathyroid)

Question 7

MEN2A

Answer 7

Mutation of germline RET (neural crest cells)

1) adrenal medulla (pheo)
2) parathyroid (tumor): 3rd and 4th pouch
3) Parafollicular cells (medullary thyroid cancer); derived from neural crest cells; associated with the 4th and 5th pouches.

Calcitonin is weak, so you get more effect from PTH, so hypercalcemia.

Question 8

Cleft lip

Answer 8

Failure of fusion of the maxillary and medial nasal processes (formation of 1st palate)

Question 9

Cleft palate

Answer 9

Failure of fusion of the lateral palatine processes, nasal septum, and/or the median palatine process
(formation of 2nd palate)

Question 10

Relationship between cleft lip and palate

Answer 10

They have two distinct etiologies but often occur together.