常见例句The yolk sac is gradually vascularized.卵黃囊逐漸被血琯化了。The gonads form from a group of large granulated yolk sac cells which invacle the germinal ridges.性腺是由一群大的顆粒的卵黃囊細胞入綴生殖峭而形成。 返回 vitelline sac