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What Do the Ovaries Do?


Updated June 09, 2014

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Question: What Do the Ovaries Do?
Answer: The ovaries are a key part of the normal development and reproductive function of women. They are a pair of glands (approximately the size and shape of an almond) in the female reproductive system where eggs are stored and estrogen is manufactured. They are held in place by several ligaments on either side of the uterus.

Many women are not aware of how important the ovaries are and how diverse their role actually is. This is one reason why PCOS can so challenging: The hormones they respond to as well as produce have an impact on so many systems.

Anatomy of the Ovaries

Eggs are transported from the ovaries to the uterus via the fallopian tubes. Surrounding the entrance to the fallopian tubes are tiny fimbrae, or finger-like projections, which guide the egg into the tube each month.

The Ovaries Through the Lifespan

A woman is born with all of the eggs she’ll ever need, around one million in each of the ovaries. By puberty, when she’ll most likely receive her first period, the number of eggs in each ovary is around 200,000 to 400,000. During her childbearing years, approximately 300 to 500 eggs will develop and be released during ovulation. After menopause, the ovaries will stop producing eggs, and atrophy (shrink).

The Ovaries' Role in the Menstrual Cycle

While cycles may be irregular in the beginning, they will eventually become more regular with about 28 days between the first days of each period. Each month, approximately 10 to 12 egg follicles will begin to develop. One will continue on to produce a mature egg. The rest will be reabsorbed into the ovarian tissue. About 14 days into a woman's cycle, that mature egg will be released in a process known as ovulation. After ovulation occurs, the empty follicle is known as a corpus luteum. It will produce progesterone and other hormones crucial for pregnancy for about 14 days. If fertilization occurs, this hormonal support will continue throughout pregnancy. If fertilization does not occur, the corpus luteum will degenerate and cause the cycle to start all over again.

Hormonal Role of the Ovaries

The ovaries are sensitive to the effects and changes of the endocrine or hormonal system. They respond to and produce their own hormones as needed by the body. In fact, the second major role of the ovary is to secrete the sex hormones, like estrogen, progesterone and very small amounts of androgens, which cause the typical female sex characteristics to develop and be maintained.

In addition, the ovaries also respond to FSH and LH which are produced by a small gland in the brain called the pituitary gland. FSH, or Follicle Stimulating Hormone, causes the estrogen level to rise and a group of egg follicles to grow each month. As one follicle becomes dominant and reaches maturity, the higher estrogen level will cause the LH (lutenizing hormone) to surge, triggering ovulation.

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