Blastoderm

Blastoderm, the term applied in Embryology (q.v.) to the flattened disc of cells resulting from the segmentation of the ovum, and in which the development of the embryo proceeds. The blastoderm divides into two layers, epiblast and hypoblast; and a third layer, the mesoblast, subsequently appears. From the epiblast are developed the cutaneous and nervous systems, from the hypoblast the epithelium of the alimentary tract with its ducts, and all other tissues of the body are derived from mesoblast.