Gastrulation
（重定向自Blastopore）
![](/Images/godic/202412/31/Blastula1138.png")
![Epithelial to Mesenchmyal Cell Transition – loss of cell adhesion leads to constriction and extrusion of newly mesenchymal cell.](/Images/godic/202412/31/Epithelial–mesenchymal_transition_scheme1138.png")
Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm.