The product of conception at any point between fertilization and birth.It includes the embryo or the fetus as well as the extraembryonic membranes. 胚胎从受精到出生期间任一阶段产物的通称，它包括了合子或胎儿甚至胚胎膜
Totipotent cell s have the capacity to specialize into extraembryonic membranes and tissues, the embryo, and all postembryonic tissues and organs. 全能细胞能够专门化胚外膜和组织，胚胎和所有胚胎后组织和器官。
The product of conception at any point between fertilization and birth. It includes the embryo or the fetus as well as the extraembryonic membranes. 胚胎从受精到出生期间任一阶段产物的通称，它包括了合子或胎儿甚至胚胎膜。
The secondary yolk sac(YS) is the first extraembryonic structure that can be detected with ultrasonography in the chorionic cavity. 卵黄囊是妊娠囊内超声能见的第一个解剖结构。
The embryos of land vertebrates are enclosed within four extraembryonic membranes that afford protection while still permitting the exchange of gases, nutrients, and other materials. 脊椎动物的胚胎被4层膜包被，起保护作用，但仍能交换气体，营养和其他物质。
