ovary

Each of the two ovaries prepares oocytes for ovulation. The special cells from which the oocytes will develop are set aside early in embryonic development, and are known as primordial germ cells. They undergo a long process of maturation in the ovary before being ovulated, and will only complete their transformation into an ovum if fertilisation takes place. An ovum has half the usual number of chromosomes - 23 - and is the female gamete.


Low-power view of sectioned ovary. There is one large fluid-filled follicle that is close to ovulation. The rectangle encloses follicles that are illustrated in the higher-power images that follow.	Immature follicles showing central primary oocytes.	Higher-power image of one follicle.	Detail at high power showing follicle cells, zona pellucida, and oocyte.	Outer germinative epithelium of ovary.