in taxon develops from Chordata ectoderm developing anatomical structure notochordal process chordamesoderm UBERON:0006268 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. A midline cellular cord formed from the migration of mesenchymal cells from the primitive knot. NCIT:C34232 EHDAA:224 VHOG:0001213 presumptive notochord