The palatine tonsils (tonsilla palatina) develop from the second pouch. A ventral protrusion (primordium of the thymus, gemma thymica major) and a dorsal protrusion (glandula parathyroidea inferior) are formed inside the third pouch. The lower parathyroid glands develop more rostrally than the upper parathyroid glands. However, they are later found in a more caudal position because they are carried downwards by migration of the thymus. The fourth pharyngeal pouch also shows a ventral and a dorsal protrusion. The ultimopharyngeal body (corpus ultimopharyngeale) and later the thymus are formed in the ventral protrusion. The ultimopharyngeal body becomes integrated into the thyroid gland and is the source of the parafollicular cells. The upper parathyroid glands (glandula parathyroidea superior) develop from the dorsal protrusion.

Pharyngeal clefts

The external acoustic meatus is formed from the first pharyngeal cleft. Its inner part provides the ectodermal coating of the tympanic membrane. Rapid growth of the second pharyngeal arch means that it extends caudally, grows over the third and fourth pharyngeal arches and amalgamates with the cardiac prominence. A temporary cavity covered with ectoderm called the cervical sinus is created, which usually disappears later.