glossary

gastrula

Definition gastrula

gastrula

gastrula n. an early stage in the development of many animal embryos. It contains a double-layered ball of cells formed by invagination and movement of cells in the preceding singular-layered stage (blastula) in the process of gastrulation. It contains a central cavity, the *archenteron, which opens through the blastopore to the outside. True gastrulation only occurs in the embryos of amphibians and certain fish, but a similar process occurs in the embryonic disc in other vertebrates, including man.