Follicles


Diagram of follicles The follicle consists of a group of cells in the ovary within which the egg (oocyte) is situated.
The primordial (or young follicles of only 0,03mm) first form in the ovary during the fourth month of gestation - about 7 million are formed. By the time of birth the number has already declined to about 2 million. By the time of the menopause only about 1000 are left. Once puberty is reached the follicles grow but only about 400 of the follicles will ever release mature oocytes.

Follicles reaching maturity ready for ovulation

The diagram on the right shows follicles at several stages of development - At first the oocyte is surrounded by only a few cells. As the follicle grow more cells are formed and gradually these cells start to secrete a fluid (shown in yellow) - in increasing quantities, until a fluid filled space is formed with the egg in the middle -See left.

At about day 12-14 the follicle is mature and erupts (or in IVF the eggs are collected/retrieved/picked up).