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.