gastrulation /gas′trəlā″shən/ [Gk, gaster, stomach] , the development of the gastrula in lower animals and the formation of the three germ layers in the embryo of humans and higher animals. It is characterized by an extensive series of coordinated morphogenetic movements within the blastula or blastocyst by which the primitive body plan of the organism is established and by which the areas that later differentiate into various structures and organs are in their proper position for development.
