Mesoderm

[Gr. mesos - middle; Gr. derma - skin] The middle germ layer, formed in the embryo during gastrulation. In early organogenesis, three regions of mesoderm are evident: the epimere (= dorsal mesoderm) will form somites; the mesomere (= intermediate mesoderm, = nephrotome) will form the excretory system; and the hypomere (= lateral plate mesoderm) delaminates into the inner splanchnic and the outer somatic mesoderm.