The endometrial cells usually implant on the peritoneum and can invade underlying tissue including bowel and bladder. This disease can result in pelvic pain, lower back pain, pain with intercourse, pain with bowel movements, infertility. Most of the uterine wall is comprised of smooth muscle. The endometrium responds to estrogen, growing thicker during the first two weeks of the menstrual cycle. After ovulation the ovarian hormone production changes from primarily estrogen to primarily progesterone.
Progesterone helps to mature the endometrium, preparing it for implantation of an embryo.
If pregnancy does not occur, the menstrual cycle begins two weeks after ovulation. The theory of retrograde menstruation states that endometriosisi arises from endometrium which is implants inside of the body after flowing back through the fallopian tubes during a woman's menstrual cycle. The function of the fallopian tube is to pick up the egg from the ovary, provide a location for fertilization and acts as an incubator, nourishing the embryo for the first couple of days of life, prior to implantation in the uterus. Follicle - A follicle is comprised of the egg, the support cells and fluid produced by the support cells. Just prior to ovulation the follicle measures about one inch in diameter.