ABSTRACT
A. The cranial portion of the embryo begins development in the middle of the third week with differentiation of three germ layers (ectoderm, endoderm, and mesoderm).
B. Neural crest cells are of ectodermal origin but consist of pluripotent ectomesenchymal tissue comparable to the three primary germ layers. Neural crest cells migrate along cleavage planes between germ layers and differentiate into connective tissue, muscle, nervous tissue, endocrine tissue, and pigment cells.
