The outer part of the ovary is covered by the germinal epithelium, which is lined by the white membrane of the ovary, and further inwards by the ovarian tissue, which is divided into a cortex and a medulla, which contains tens of thousands of primordial follicles. The development of follicles in the human ovary begins during the embryonic period, and the ovary contains approximately 150,000-500,000 follicles at birth. In childhood, the cortex of the ovary contains a large number of densely packed primordial follicles, and the medulla of the ovary has gradually degenerated. The primordial follicle contains a single oocyte surrounded by a layer of spindle-shaped or flattened cells. After puberty, the number of oocytes gradually decreases. Only about 300-400 oocytes mature during the reproductive period and are expelled through the process of ovulation, while the rest of the follicles degenerate on their own to a certain extent, a process called follicular atresia. It is generally believed that only a few follicles mature in each cycle of a normal woman’s reproductive life and only one of them ovulates, while the rest of the equally mature follicles do not ovulate and degenerate. At menopause, the ovarian cortex thins and the primordial follicles are depleted. The few remaining follicles are insensitive to gonadotropins, and follicular maturation becomes impaired and ovulation no longer occurs. Although the number of primordial follicles in the ovary is extremely high, usually only 300-400 oocytes are developed and expelled during a woman’s lifetime.