The amniotic cavity, which is initially located dorsal to the germinal disk, grows rapidly and eventually encircles the fetus, obliterates the chorionic cavity, and envelops the umbilical cord.

• 最开始位于胚盘背侧的羊膜腔迅速生长，最终包绕胎儿，使绒毛膜封闭并包裹脐带。