Pharyngeal pouches

The side wall of the pharynx forms pharyngeal pouches between the pharyngeal arches. These pouches are outgrowths of the endoderm that match up to the corresponding exterior ectodermal pharyngeal clefts. The auditory tube (tuba auditiva) and the tympanic cavity are formed from the first pouch. The tympanic membrane develops at the point where ectoderm and endoderm meet.