This inward movement of cells is due to innate forces within various cell groups.Įmbolic movement (Fig. Emboly refers to the inward movement of the presumptive chorda-mesodermal and endodermal areas (refer fate map page 540) and their extension along the anteroposterior axis of the future embryo. The word emboly is derived from a Greek word meaning to throw in or thrust in. These internal forces in turn are correlated with external conditions.
Gastrulation is a well-integrated process, controlled largely by intrinsic (i.e., autonomous) forces. Thus, gastrulation is the embryo’s way of laying down its body plan. Gastrulation can be defined “as the dynamic process during which the major, presumptive organ-forming areas of the blastula become rearranged and reorganized in a way which permits their ready conversion into the body plan of the particular species” (Nelsen, 1953).” During gastrulation the blastocoelic cavity is obliterated and a new cavity called archenteron is formed. The numerous cells of the blastula formed due to cleavage, are given new positions and neighbours during gastrulation resulting in the establishment of the multi-layered body plan of the adult organism. It is a process of highly coordinated cell and tissue movement whereby the cells of the blastula are rearranged to form the-three germ layers ectoderm, mesoderm and endoderm. The term gastrulation is applied to the process which produces the gastrula (Greek: gaster, stomach).
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