Which pouch forms the thymus and inferior parathyroids?

Which pouch forms the thymus and inferior parathyroids?

• A. Third pouch
• B. Fourth pouch
• C. Second pouch
• D. First pouch

Answer: (A)

Gland development from the pharyngeal pouches shows that the third pouch gives rise to thymic tissue and the inferior parathyroid glands. The thymus originates from the ventral part of the third pouch and migrates downward into the anterior mediastinum, pulling thymic tissue with it. The dorsal part of the same pouch forms the inferior parathyroids, which remain associated with the lower pole of the thyroid. In contrast, the fourth pouch supplies the superior parathyroids and the parafollicular (C) cells of the thyroid. So, the pouch that forms both the thymus and the inferior parathyroids is the third pouch.

Gland development from the pharyngeal pouches shows that the third pouch gives rise to thymic tissue and the inferior parathyroid glands. The thymus originates from the ventral part of the third pouch and migrates downward into the anterior mediastinum, pulling thymic tissue with it. The dorsal part of the same pouch forms the inferior parathyroids, which remain associated with the lower pole of the thyroid. In contrast, the fourth pouch supplies the superior parathyroids and the parafollicular (C) cells of the thyroid. So, the pouch that forms both the thymus and the inferior parathyroids is the third pouch.