Blastopore

A temporary opening on the surface of gastrula through which the internal cavity (the archenteron) communicates with the exterior (see figure below).  Its dorsal lip in amphibians was shown by Hans Spemann (1869-1941) to be the site of induction of overlying tissue during gastrulation.  It is the source of the dorsalizing proteins chord in and noggin that bind to the centralising protein BMP-4.

A blastopore on the surface of gastrula

See Archenteron, Bone Morphogenetic Proteins (BMPs), Chordin, Ectoderm, Entoderm (or endoderm), Gastrula, Gastrulation, Germinal (or germ) layers, Hensen’s node, Induction (embryology), Mesoderm, Neural crest, Neural plate, Neural tube, Noggin, Organizer (embryology)