germ-layer

基本解释

Mesoderm --- The middle germ layer in the early embryo; the source of cells that go on to make bones, muscles, connective tissue, heart, hematopoietic system, kidney, and other organs.
原肠胚形成过程中，由上胚层细胞增殖产生的一部分细胞在上、下胚层之间形成的第三层细胞。通常形成骨骼、肌肉、结缔组织、心脏、造血系统、肾脏和其它器官。
Germ layer --- One of three distinct layers of cells that arise in the inner cell mass, the ectoderm, mesoderm, and endoderm, each of which develops into a distinctly different tissue in the embryo.
胚胎发育到原肠胚时的细胞层，分为内胚层、中胚层、外胚层，各胚层将发育成一定的组织器官。

any of the three layers of cells formed during gastrulation &rarrsee ectoderm , mesoderm , endoderm