How it works

The production of ova in females begins at the foetal stage itself — long before birth.

At birth there are about 200,000 to 400,000 primary follicles in one ovary. No more are ever made. Everything that follows is a matter of releasing them, a very few at a time, over several decades.

Close to the time of reaching puberty, a primary follicle develops into a structure containing a group of cells, called the Graafian follicle. It lies close to the periphery of the ovary.
Once mature, the Graafian follicle bursts and releases the ovum within it from the ovary.
The fimbriae direct it into the fallopian tube.
The ovum then travels along the fallopian tube towards the uterus.

Figure to be added

Figure 14.24 — a transverse section of an ovary showing the various stages of an ovum: the primary follicles, the Graafian follicle, the released ovum, the developing corpus luteum, the corpus luteum and the corpus albicans.

A fixed supply, unlike sperm

This is the sharpest contrast with the male system. Sperm are made continuously from puberty onwards, in millions. Ova are all present at birth and only released — which is why the number of ova a person will ever have was settled before they were born.