So you'd think–no yolk, no yolk sac.

所以你会认为我们不需要卵黄，也不需要卵黄囊。

Humans make an empty yolk sac, and it disappears halfway through pregnancy.

人类在孕期会产生一个空卵黄囊，但是中途就消失了。

Inside a chicken egg, the growing embryo produces something called a yolk sac.

在鸡蛋里面，成长的胚胎产生一种名为卵黄囊的东西。

The second subtype is a yolk sac tumor, also called an endodermal sinus tumor, and it's made of germ cells that differentiate into yolk sac tissue.

第二种亚型是卵黄囊瘤，也称为内胚层窦瘤，是由分化为卵黄囊的生殖细胞组成。

Each egg contains one embryo and a yolk sac which the embryo feeds off and helps it develop inside the egg.

每枚卵中含有一个胚胎和一个卵黄囊，胚胎从卵黄囊中汲取营养，从而得以在卵中发育。

The four major types of germ cell tumors are: fetal teratomas, both mature cystic and immature teratomas; yolk sac tumors, or endodermal sinus tumor, choriocarcinoma or placental tissue tumors and finally dysgerminomas or oocyte tumors.

4种卵巢细胞癌如下：畸胎瘤，包括成熟囊性畸胎瘤和未成熟畸胎瘤；卵黄囊瘤，又叫内胚窦瘤；绒毛膜癌，又叫胎盘组织肿瘤；最后是无性细胞瘤，又叫卵母细胞瘤。