Women's Health

Pelvic Pain & Vulvar Disease Center

Endometriosis

The Female Reproductive Organs

The uterus is a pear shaped organ in the center of the pelvis. The lower part of the uterus is called the cervix and protrudes into the upper vagina. The two fallopian tubes are attached to the fundus (the upper part of the uterus), one on each side. The ends of the tubes open into the abdominal cavity near the ovaries. The two ovaries are 2 inch-sized glands, attached to the uterus, one on each side, beneath the openings of the fallopian tubes. The ovary serves two functions that are closely linked, the production of eggs and the secretion of hormones.

The Female Reproductive Cycle

Why some women get endometriosis is not known, but its growth and spread are dependent on the female hormones produced cyclically each month by the ovaries. The two main hormones produced by the ovary are estrogen and progesterone. Estrogen is produced in both the first and second half of the cycle and progesterone in the second. Each month, in the middle of the cycle, a mature egg is released by the ovary, known as ovulation. The tube catches the egg and draws it inside. If the egg is fertilized it may embed in the lining of the womb, the endometrium, and a pregnancy has commenced. If it is not fertilized, it is lost together with the endometrium at the time of menses at the end of the cycle.

Endometriosis also goes through a cycle each month and grows under the influence of the hormone estrogen. It may also bleed each month at the time of menses, but there is no escape for the blood, so it remains at the area of endometriosis and irritates the surrounding tissues.