Blastula vs. Gastrula

Blastulanoun

(embryology) An early form in the development of an embryo, consisting of a spherical layer of cells filled with fluid; a blastosphere.

Blastulanoun

That stage in the development of the ovum in which the outer cells of the morula become more defined and form the blastoderm.

Blastulanoun

early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs

Gastrulanoun

(embryology) A stage in the development of embryos of most animals consisting of a three-layered sac of ectoderm, mesoderm and endoderm.

Gastrulanoun

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.

Gastrulanoun

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