gastrula /gas·tru·la/ (gas´troo-lah) the embryo in the stage following the blastula or blastocyst; the simplest type consists of two layers of cells, the ectoderm and endoderm, which have invaginated to form the archenteron and an opening, the blastopore. In human embryos the gastrula stage occurs during the third week, as the embryonic disc becomes trilaminar, establishing the ectoderm, mesoderm, and endoderm.
gastrula
gas·tru·la (g s tr -l)n. pl. gas·tru·las or gas·tru·lae (-l   ) An embryo at the stage following the blastula, consisting of a hollow, two-layered sac of ectoderm and endoderm surrounding an archenteron that communicates with the exterior through the blastopore. |
gastrula
[gas′troo͡lə]
Etymology: Gk, gaster, stomach
the early embryonic stage formed by the invagination of the blastula. The cup-shaped gastrula consists of an outer layer of ectoderm and an inner layer of mesentoderm that subsequently differentiate into the mesoderm and endoderm. See also blastula, embryonic layer.
gastrula
an embryo in the stage following the blastula stage; the simplest type consists of two layers of cells, the ectoderm and entoderm, which have invaginated to form the archenteron and an opening, the blastopore.
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