Pronunciation: GAS-tru-la

Etymology: It is the Latin diminutive (diminutive ending -ula) of a Greek root, gaster (γαστήρ), which means belly, stomach, or womb. Thus, gastrula literally means “little belly” and is a reference to the invagination of the blastula forming the archenteron, the first stomach (see below).

The gastrula is a ball of cells that develops from the blastula. It is initiated by the formation of the blastopore that can develop into a complete food tube or become arrested as a gastrovascular cavity. The gastrula also is the point at which the embryo forms two cell layers (in the Radiata) or three cell layers in the Bilateria (Prototostomata and Deuterostomata).

By Jack R. Holt. Last revised: 01/02/2009