The layer of flat cells of mesodermal origin that lines the embryonic body cavity and gives rise to the squamous cells of the peritoneum, pericardium, and pleura.

• 间皮起源于中胚层的扁平细胞层，衬于胚胎的原始体腔中，最终发育成腹膜、心包及胸膜的上皮细胞