Uterus

The hollow, muscular organ of the female reproductive system in which the fertilized ovum (egg) normally becomes embedded and in which the embryo and fetus develop. The uterus is commonly known as the womb. It is situated in the pelvic cavity, behind the bladder and in front of the intestines. In a nonpregnant woman, the uterus is 7.5–10 cm long and weighs 60–90 g. The lower part opens into the vagina at the cervix; the upper part opens into the fallopian tubes. The inside is lined with endometrium. The uterus expands in size during pregnancy to accommodate the growing baby. At full-term, the powerful uterine muscles expel the baby via the birth canal (see childbirth). After the menopause, the endometrium atrophies (becomes thinner) and the uterine muscle and connective tissue are reduced. Conditions that affect the uterus include congenital disorders, such as malformation or absence of the uterus; tumours, including polyps, fibroids, and cancer of the endometrium (see uterus, cancer of); infections, causing endometritis; and hormonal disorders. (See also uterus, prolapse of; uterus, retroverted.)