A

The epithelium of the dorsal (distal) portion of the second pharyngeal pouch proliferates and forms the tonsillar fossa and palatine tonsil, while its ventral part is largely obliterated; the thymus comes from the ventral third pouch, and the tubotympanic recess and tympanic antrum derive from the first pouch [Iemma et al., 1992, PMID 1577632].