part_of part of part of has_part has part has part develops_from develops from develops from embryonic structure pharyngeal arch endoderm of foregut pharyngeal pouch branchial pouch visceral pouch visceral pouches An internal pocketing of pharyngeal endoderm that contacts a region of ectoderm (a pharyngeal cleft) and interdigitates in the anterior and posterior directions with the pharyngeal arches. pharyngeal pouches embryonic tissue early pharyngeal endoderm pharyngeal arch system