Transformation of the blastula into the gastrula; the development and invagination of the embryonic germ layers.
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gas·tru·la·tion .gas-trə-'lā-shən n the process of becoming or of forming a gastrula
gas·tru·late 'gas-trə-.lāt vi, -lat·ed; -lat·ing
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gas·tru·la·tion (gas″troo-laґshən) the process by which a blastula becomes a gastrula or, in forms without a true blastula, the process by which three germ cell layers are acquired. In humans, it denotes the conversion of the bilaminar embryonic disc into a trilaminar embryonic disc as cells from the epiblast migrate through the primitive streak to become ectoderm, mesoderm, and endoderm.Medical dictionary. 2011.