The tissue that normally lines the inside of the uterus is called the endometrium.
In some women the endometrium grows outside of the uterus. When this happens a woman has a condition called endometriosis. The most common areas for this abnormal growth of endo metrium are the reproductive organs (the ovaries, fallopian tubes, and uterus). Endometrium may also grow on the intestines, bladder, rectum, and the lining of the pelvic area and abdomen.
This misplaced tissue responds to the hormones of the menstrual cycle and bleeds each month in the same way the lining of the uterus responds to hormones. However, if the tissue is not in the uterus, the blood shed from the tissue has no way to leave the body. When the tissue bleeds, cysts, adhesions, and scar tissue form and the area around the endometriosis thickens. Very rarely, eodometriosis becomes cancerous.
How does it occur?
Why some women develop endometriosis is not known. There are many theories, but none of them explains all cases. Some of the theories are:
- In some women during menstruation, some of the menstrual tissue backs up through the fallopian tubes and into the abdomen, where it attaches and grows.
- Endometriosis may be a genetic process or some families may have predisposing factors to endometriosis.
- Endometrial cells spread to other parts of the body through the lymph system or blood vessels.
- There is some endometrial tissue in the uterus that backs up in all women. The immune system may then destroy the misplaced tissue. Women who develop endometriosis, however, may have an immune system that is not able to destroy the misplaced tissue.