Which pharyngeal pouch forms the auditory (Eustachian) tube?

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

Answer: (A)

The auditory (Eustachian) tube comes from the first pharyngeal pouch. As the pouch deepens, it forms the tubotympanic recess, which differentiates into the tympanic (middle ear) cavity and the auditory tube. The proximal portion becomes the middle ear cavity, while the distal portion develops into the cartilaginous and bony parts of the auditory tube that connect the middle ear to the nasopharynx, enabling pressure equalization. In contrast, the second pouch mainly contributes to structures related to the palatine tonsil, the third pouch to the thymus and inferior parathyroids, and the fourth pouch to the superior parathyroids and the C cells of the thyroid, so they are not involved in forming the auditory tube.