Ovarian cancer

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Anatomy and physiology of the ovary

The ovaries are the organs in a woman’s reproductive system that produce eggs (ova.) They are almond-shaped and about 3.5 cm (1.5 inches) long. The ovaries are deep in a woman’s pelvis, on both sides of the uterus (womb), close to the ends of the Fallopian tubes.

Diagram of the female reproductive system


The ovaries are made up of 3 different types of cells:

  • Epithelial cells make up the outer layer covering the ovary (epithelium).
  • Germ cells are inside the ovary. They develop into eggs.
  • Stromal cells form the supportive or connective tissues of the ovary (stroma).

Each ovary is surrounded by a thin layer of tissue called the capsule.

Diagram of cross-section of the ovary


The ovaries have 2 main functions. They produce mature eggs. They also make the female sex hormones, which control reproduction and sexual development.

Estrogen is responsible for the development of secondary sex characteristics, such as the growth of breasts.

Progesterone prepares the body for conception by causing the buildup of the uterine lining (endometrium) and other changes.

The ovaries are the main source of estrogen in sexually mature women.

Each month during ovulation, an ovary releases a mature egg. The egg travels down the Fallopian tube to the uterus. If it is fertilized by a sperm, the egg implants into the lining of the uterus and begins to develop into a fetus. If the egg is not fertilized, it is shed from the body along with the lining of the uterus during menstruation.

During menopause, the ovaries stop releasing eggs and producing sex hormones.


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