The formation of ovum from oogonia in females takes place by a process called oogenesis, which occurs in the ovary. During the process a diploid oogonium or egg mother cells increases in size and transforms into a diploid primary oocyte, the later then undergoes meiosis I or reductional division to form two unequal haploid cells. The smaller cell is called “first polar body” and the larger cell is called “secondary oocyte”. The secondary oocyte undergoes meiosis II or equational division to form a secondary polar body and an ovum.

Flow chart presentation of oogenesis :