Question
The most common development of gland marked as “A” in the picture below is from which of the structures?
A. Brachial cyst.
B. Brachial cleft.
C. Brachial pouch.
D. Brachial arch.
Show Answer
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Correct Answer » C
Explanation
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Anc;C. Brachial pouch
The gland marked as “A” in the picture above represents the Parathyroid gland.
- The parathyroid glands develop from the endoderm of the third and fourth pharyngeal pouches (Brachial Pouch). The thymus is also derived from the third pharyngeal pouch.
- The endodermally lined pharyngeal pouches, transient in nature, give rise to important structures. The derivatives of the pharyngeal pouches has a dorsal and a ventral part.
| Pouch 1 |
ventral |
Obliterated: no derivative |
|
dorsal |
pharyngotympanic tube and middle ear cavity |
| Pouch 2 |
Ventral |
palatine tonsil,partially obliterated by endoderm |
|
dorsal |
contributes to pharyngotympanic tube |
| Pouch 3 |
Ventral |
thymus |
|
dorsal |
inferior parathyroid gland |
| Pouch 4 |
ventral |
ultimobranchialbodies (C-cells of thyroid gland) |
|
dorsal |
superior parathyroid gland |
