Anatomy of the Uterus
Cross Section of the Female Reproductive System
(Courtesy of Jones and Bartlett Publishers)
The uterus is part of the female reproductive system. You may know it as the womb. It is normally pear-shaped and about the size of a fist. It is in your pelvic area, between your bladder and your rectum. At the top of each side of your uterus are connections to your fallopian tubes. The other side of your fallopian tubes attach to your ovaries. The bottom of the uterus is called the cervix. It connects to your vagina. The uterus wall has 3 layers:
- Endometrium, the inner lining
- Myometrium, the middle muscle layer
- Serosa, the outer smooth layer
If you have not reached menopause, it is normal that every month your ovary drops an egg into the fallopian tubes. Under the influence of hormones produced by the ovary, the endometrium changes. The change prepares it to receive a fertilized egg. If the egg isn’t fertilized you do not become pregnant. In that case, the lining is shed as your menstrual period. With menopause, the normal cycle of the ovaries stops. Without the constant influence of hormones (estrogen and progesterone), the endometrium thins out and your periods stop.
If you have estrogen or hormone replacement therapy, the endometrium may be stimulated by the hormones you take. Or it can be stimulated by conversion of hormones produced by the adrenal gland. These hormones are converted to estrogens by fatty tissues in the body. In some women, the stimulation by hormones can lead to abnormal bleeding. It can also lead to precancerous growth, or to cancer of the endometrium. For women taking hormone replacement therapy who have not had a hysterectomy, a progesterone medication is used to offset the effects of estrogen.
