During descent, how is the inferior parathyroid incorporated?

• A. It attaches to the ventral surface of the thyroid
• B. It is pulled down with the thymus and attaches to the dorsal surface of the thyroid
• C. It migrates to the posterior mediastinum
• D. It remains in the neck separately from the thymus

Answer: (B)

During development, the inferior parathyroid glands arise with the thymus from the third pharyngeal pouch. As the thymus descends into the chest, it pulls the inferior parathyroids along with it. When they reach their final position, the inferior parathyroids typically lie on the dorsal (posterior) surface of the thyroid gland, near its lower poles. This is why the description of being pulled down with the thymus and attaching to the dorsal surface of the thyroid fits best. They don’t end up on the ventral surface, nor do they migrate into the posterior mediastinum or stay isolated in the neck separate from the thymus.