Endometriosis

The endometrium is the mucous membrane which normally lines the uterine cavity and which is rejected once a month during menstruation. Endometriosis, on the other hand, is the occurrence of uterine lining islands outside the uterine cavity. The preferred sites are the inner lining of the abdominal cavity in the pelvis (peritoneal endometriosis), the ovaries, where typical cysts form (endometriosis cysts), the tissue separating the vaginal wall from the rectum (rectovaginal endometriosis), and the muscles of the uterus itself (adenomyosis uteri).