gastrulaatio
Gastrulaatio, or gastrulation, is a key stage in animal embryogenesis. During gastrulation, the blastula, a hollow ball of cells, reorganizes into a multilayered structure called the gastrula. This transition establishes the three primary germ layers—ectoderm, mesoderm, and endoderm—and sets up the major body axes. Gastrulation follows cleavage and precedes organogenesis, with timing that varies among species.
The process involves coordinated cell movements and shape changes, such as invagination (folding inward), involution (sheet
In many animals, an organizer region directs patterning: the primitive streak in birds and mammals or analogous
Gastrulation exhibits variation across taxa, but remains a conserved mechanism for transforming a simple blastula into