Pronunciation: BLAS-tu-la.

Etymology: The term is derived from the Greek root, blastos (βλαστός) which means a sprout, bud, or shoot. The -ula ending is the dimuitive Latin ending. So, it literally means little sprout or bud. The reference is to the blastula being the “bud” from which an animal develops.

The blastula is a hollow, fluid-filled ball of cells that develops from the zygote of Metazoans. From here, the blastula may develop into a gastrula by the formation of a blastopore.

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