卵子发生

例句：

1. 1. The female mouse has a ovary that produces eggs and sperm.
   雌性老鼠有一个卵巢，产生卵子和精子。
2. 2. During the oocyte maturation stage, the egg is surrounded by a layer of cumulus cells.
   在卵母细胞成熟阶段，卵子被一层颗粒细胞包围。
3. 3. In humans, fertilization occurs when an egg is matured and ready to be fertilizedby a sperm.
   在人类中，受精发生在卵子成熟并准备好被精子受精的时候。