mesectoderm

例句：

1. 1. The mesoderm is the layer of cells that gives rise to all the body's internal organs.
   中胚层是产生所有身体内部器官的细胞层。
2. 2. In embryology, the mesoderm is the first layer of cells to form after the ectoderm.
   在胚胎学中，中胚层是外胚层形成后的第一批细胞。
3. 3. The mesoderm also plays a crucial role in the development of the nervous system.
   中胚层在神经系统的发展中起着至关重要的作用。