Uterus or Womb, flattened, pear-shaped, hollow organ in the pelvis of the human female and most other mammals. In pregnancy, it is the organ that holds the unborn developing child (see Pregnancy and Childbirth).
The uterus consists of a body, a base or fundus, a neck or cervix, and a mouth. Suspended in the pelvis, it lies with the base directed upward and forward and the cervix directed slightly backward. It is connected to the vagina by the cervix. On either side of the uterus lies an ovary. Eggs produced by the ovaries reach the uterus through the fallopian tubes. In the unimpregnated condition the uterus is about 7.6 cm (about 3 in) in length, 5 cm (2 in) in breadth, and 2.5 cm (1 in) in thickness. In pregnancy the fertilized egg implants itself in the lining of the uterus, where it grows to maturity; the walls of the uterus are elastic and stretch during pregnancy to hold the developing child. The uterus body consists of a firm outer coat of muscle, known as the myometrium, and an inner lining of soft, glandular material, known as the endometrium, that thickens with blood during ovulation, preparatory to receiving a fertilized ovum. If fertilization does not occur, this lining breaks down in menstruation.
The uterus is prone to infection. Endometritis, an inflammation of the mucous lining of the uterus, may affect either the neck or the body of the organ or both. Cancer and fibroid tumors of the uterus are comparatively frequent.
See also Reproductive System.