Endometriosis - Introduction
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Location of Implants
Implants can form in many areas, most commonly in the following:
- The peritoneum. This is the smooth surface lining that covers the entire wall of the abdomen and folds over inner organs in the pelvic area.
- On or next to the ovaries.
Less commonly they occur in other areas:
- Cul-de-sac, an area between the uterus and rectum
- Connective tissue that supports the uterus (called the uterosacral ligaments)
- Vagina
- Fallopian tube
- Urinary tract (in about 20% of cases, usually without causing symptoms).
- Gastrointestinal tract (in 12 - 37% of patients)
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Click the icon to see an image of the female reproductive anatomy. |
Very rarely, they appear in areas far from the pelvis, including the lungs and even the arms and thighs.
Process of Endometriosis
The process of endometriosis mimics menstruation at certain stages:
- Each month, the exiled endometrial implants respond to the monthly cycle just as they would in the uterus. They fill with blood, thicken, break down and bleed.
- Products of the endometrial process cannot be shed through the vagina as menstrual blood and debris do. Instead, the implants develop into collections of blood that form cysts, spots, or patches.
- Lesions may grow or reseed as the cycle continues.
The lesions are not cancerous, but they can develop to the point that they cause obstruction or adhesions (web-like scar tissue) that attach to nearby organs, causing pain, inflammation, and sometimes infertility.
The Female Reproductive System
The primary structures in the reproductive system are as follows:
- The uterus is a pear-shaped organ located between the bladder and lower intestine. It consists of two parts, the body and the cervix.
- When a woman is not pregnant the body of the uterus is about the size of a fist, with its walls collapsed and flattened against each other. During pregnancy the walls of the uterus are pushed apart as the fetus grows.
- The cervix is the lower portion of the uterus. It has a canal opening into the vagina with an opening called the os, which allows menstrual blood to flow out of the uterus into the vagina.
- Leading off each side of the body of the uterus are two tubes known as the fallopian tubes. Near the end of each tube is an ovary.
- Ovaries are egg-producing organs that hold between 200,000 and 400,000 follicles (from folliculus, meaning "sack" in Latin). These cellular sacks contain the materials needed to produce ripened eggs, or ova.
The inner lining of the uterus is called the endometrium, and during pregnancy it thickens and becomes enriched with blood vessels to house and support the growing fetus. If pregnancy does not occur, the endometrium is shed as part of the menstrual flow. Menstrual flow also consists of blood and mucus from the cervix and vagina.
Reproductive Hormones
The hypothalamus (an area in the brain) and the pituitary gland regulate the reproductive hormones. The pituitary gland is often referred to as the master gland because of its important role in many vital functions, many of which require hormones. In women, six key hormones serve as chemical messengers that regulate the reproductive system:
- The hypothalamus first releases the gonadotropin-releasing hormone (GnRH).
- This chemical, in turn, stimulates the pituitary gland to produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
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Estrogen, progesterone, and the male hormone testosterone are secreted by the ovaries at the command of FSH and LH and complete the hormonal group necessary for reproductive health.
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Review Date: 06/13/2006
Reviewed By: Harvey Simon, M.D., Associate Professor of Medicine, Harvard
Medical School; Physician, Massachusetts General Hospital
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