Gastrulation is the process by which a blastula converts into gastrula. During gastrulation, a three-layered embryo made of ectoderm, mesoderm, and endoderm enclosing a new cavity called archenteron is formed. The lumen of the archenteron forms the future gut, which opens outside through the blastopore. In protostomes, the blastopore becomes the mouth and in deuterostomes, the anus.
