primary ovum

biology

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 13, 2026

Quick Summary

Oogenesis is the biological process in human females where a primary egg cell, or ovum, matures into a fully developed ovum ready for fertilization. This development begins before birth, with all the egg cells present in the ovaries at birth numbering around 400,000. These are called primary ova and remain dormant until ovulation.1

When ovulation occurs, the primary ovum undergoes cell division. This results in a larger secondary ovum and a smaller polar body. The secondary ovum then matures within the ovary before being released into the fallopian tube, where it can be fertilized by sperm. This entire process is regulated by hormones such as FSH and LH.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

2 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

oogenesis
These cells, known as the primary ova, number around 400,000. The primary ova remain dormant until just prior to ovulation, when an egg is released from the ovary. Some egg cells may not mature for 40 years; others degenerate and never mature.
Read More
These cells, known as the primary ova, number around 400,000. The primary ova remain dormant until just prior to ovulation, when an egg is released from the ovary. Some egg cells may not mature for 40 years; others degenerate and never mature.
Read More