Female meiosis (oogenesis)

A diploid primary oocyte undergoes meiosis I in the ovary.

One of the haploid daughter cells receives most of the cytoplasm and is called a secondary oocyte; the other is a nonfunctional polar body.

The secondary oocyte is released from the ovary in a process called ovulation.

Meiosis II occurs only if the secondary oocyte is penetrated by a sperm, forming another polar body and an unfertilized egg called an ovum.