part of develops from ends during starts during oral evagination mouth primordium embryonic structure buccopharyngeal membrane UBERON:0006211 xenopus_anatomy A 1-2 cell layer membrane comprising cells from the stomodeum and underlying endodermal layer. Perforation of this structure creates an opening connecting the external and the digestive tube which is essential for oral cavity formation. oral plate membrane XAO:0005291 NF stage 37 and 38 NF stage 40