Ovary (human)
The human ovary is the femalegonad, and is an important part of the reproductive system. Ordinarily, women have a pair of ovaries. Situated in the pelvis, this pair of organs have a changing role throughout the lifespan. During the childbearing years, from menarche to menopause, the ovaries produce ovum, the mature egg cell that, if fertilized by a sperm cell, can develop into a baby. The ovaries also are a major source of the hormones estrogen and progesterone, that are produced in varying levels throughout the ovulatory cycle.
The development of the ovaries in the embryo
The ovaries in infancy and childhood
At birth, each ovary contains approximately 2 million follicles - most of them in the outer layer of the organ, which is called the cortex of the ovary. Each ovary is suspended with its respective fallopian tube in a flexble sheet of connective tissue that contains the arterial and venous vasculature that supply blood circulation to the organ.
Streak ovaries
The ovaries in adolescence
The ovaries undergo a major change with the coming of puberty. The initial period of the menstrual cycle, which ushers in the female milestone called menarche, is usually anovulatory - that is, no ovum are produced.
Adult ovaries
Ovarian failure: Menopause and after
In the lifespan of every normal woman who ives long enough, the ovaries are said to "fail". This medical term has a harsh tone, but simply refers to the loss of the ovulatory cycle. With aging, the primordial follicle population continues to become smaller, and once the number of oocytes falls below threshold population, then the menstrual cycle ceases and menopause occurs. "Premature ovarian failure, which is defined as cessation of menstruation (hypergonadotrophic amenorrhea) before the age of 40 years, occurs in up to 0.9% of women in the general population and has multiple causes."(Marhhom E. Cohen I. Fertility preservation options for women with malignancies. Obstetrical & Gynecological Survey. 62(1):58-72, 2007 Jan. UI: 17176489).
As the ovaries begin to decline in function, serum levels of FSH rise in the early part of the ovulatory cycle, because a higher level is needed to recruit follicles. On day 3 of the menstrual cycle, serum FSH levels are usually less than 10 mIU per ml. FSH levels that are more than 15 mIU per mL on day 3 suggest decreased ovarian reserve.