An embryonic form having its origin in the invagination or pushing in of the wall of the planula or blastula (the blastosphere) on one side, thus giving rise to a double-walled sac, with one opening or mouth (the blastopore) which leads into the cavity (the archenteron) lined by the inner wall (the hypoblast). See Illust. under Invagination. In a more general sense, an ideal stage in embryonic development. See Gastræa.
Embryo that is in the process of regionalizing into three germ layers (ectoderm, mesoderm and endoderm).
the embryonic stage of an animal that has cells differentiated into germ layers. Sequentially, It follows the blastula stage An early gastrula. The cells at the vegetal hemisphere have begun to invaginate into the blastocoel, forming the archenteron. (Photo: Dr. Anna E. Ross, Christian Brothers University, TN)
(Greek, gastrula = little stomach) A stage of an animal embryo in which the three germ layers have just formed.
(gas´ true luh) [Gr. gaster: stomach] • An embryo forming the characteristic three cell layers (ectoderm, endoderm, and mesoderm) which will give rise to all of the major tissue systems of the adult animal.
Stage in development when there are three distinct germ layers
GAS-troo-la A three-layered embryo. 220
(Gr. gaster, stomach). A trilaminar embryonic (ectoderm, mesoderm and endoderm) disc that differentiates into the tissues and organs of the embryo.
An early stage of the developing embryo that follows the blastula stage.
(plural: gastrulae gastrula - the belly, stomach] The early embryonic stage following the blastula stage during which cell migrations form distinct germ layers. The primitive gut (archenteron) is formed and opens to the exterior through the blastopore.
bisc333 double-walled stage of the embryo resulting from invagination of the blastula; the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm www.cogsci.princeton.edu/cgi-bin/webwn
The gastrula phase of embryonic development is seen in all animals except the sponges. It follows the blastula phase. The purpose of gastrulation is to position the three embryonic germ layers, the endoderm, ectoderm and mesoderm.
