The formation on endodermal and ectodermal germ layers occurs at ________.

A) fertilization
B) gastrulation
C) cleavage
D) blastula formation

Endodermal

Pertaining to the innermost layer of the three primary germ layers in the very early embryo, which gives rise to the digestive and respiratory systems among others.

Ectodermal

Pertaining to the ectoderm, the outermost layer of the embryo, giving rise to the nervous system, skin, and various sensory organs.

Germ Layers

The three primary layers of cells (ectoderm, mesoderm, and endoderm) in the early embryo from which all tissues and organs develop.