A thin,tough,membranous sac that encloses the embryo or fetus of a mammal,bird,or reptile. It is filled with a serous fluid in which the embryo is suspended.

• 羊膜，一层薄的、坚韧的膜囊，可包住哺乳动物、鸟类或爬行动物的胚胎或婴儿，膜囊被羊水充满，胚胎悬浮其中。