To better understand endometriosis, it helps to understand the anatomy of the uterus.
The uterus, or womb, is part of the female reproductive system. The cervix is the lowest part of the uterus. The ovaries, fallopian tubes and vagina are the other parts of the female reproductive system.
The inner lining of the uterus is called the endometrium. Before ovulation, the endometrium grows and becomes thick. If fertilization does not occur than the endometrium is shed during a menstrual period. If an egg is fertilized, the endometrial tissue and blood vessels support the fertilized egg after it has implanted in the uterus.
- Moore J, Copley S, Morris J, Lindsell D, Golding S, Kennedy S. A systematic review of the accuracy of ultrasound in the diagnosis of endometriosis. Ultrasound Obstet Gynecol. 2002 Dec;20(6):630-4. 
- Schroder AK, Diedrich K, Ludwig M. Medical management of endometriosis: a systematic review. IDrugs. 2004 May;7(5):451-63. 
- Wykes CB, Clark TJ, Khan KS. Accuracy of laparoscopy in the diagnosis of endometriosis: a systematic quantitative review. BJOG. 2004 Nov;111(11):1204-12.