The middle embryonic germ layer,lying between the ectoderm and the endoderm,from which connective tissue,muscle,bone,and the urogenital and circulatory systems develop.

• 中胚层中间胚芽层，位于外胚层和内胚层之间，最终发育成结缔组织、肌肉、骨骼、泌尿系统及循环系统。