develops_from ectoderm developing anatomical structure notochordal process A midline cellular cord formed from the migration of mesenchymal cells from the primitive knot EHDAA2:0001279 EHDAA:224 EMAPA:16102 FMA:293135 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. UBERON:0006268 UMLS:C1518430 VHOG:0001213 chordamesoderm presumptive notochord uberon