1. An early stage of embryonic development in which a three-layered structure forms from a blastula, consisting of the ectoderm, mesoderm, and endoderm.
Usage: biology; developmental biology

Examples

• The gastrula stage follows the blastula in animal development.
• During gastrulation, cells migrate to form the three primary germ layers.
• Scientists study the gastrula to understand how organs begin to form.
• The gastrula is a critical stage in the development of most animals.
• In the gastrula, the endoderm will eventually give rise to the digestive system.