only_in_taxon only in taxon develops_from develops from develops from Chordata ectoderm developing anatomical structure notochordal process chordamesoderm uberon UBERON:0006268 A midline cellular cord formed from the migration of mesenchymal cells from the primitive knot. UMLS:C1518430 presumptive notochord A midline cellular cord formed from the migration of mesenchymal cells from the primitive knot EMAPA:16102 FMA:293135 EHDAA2:0001279 The notochordal process grows cranially until it reaches the prechordal plate, the future site of the mouth. In this area the ectoderm is attached directly to the endoderm without intervening mesoderm. This area is known as the oropharyngeal membrane, and it will break down to become the mouth. At the other end of the primitive streak the ectoderm is also fused directly to the endoderm; this is known as the cloacal membrane (proctodeum), or primordial anus. NCIT:C34232 EHDAA:224 VHOG:0001213