The uterus is part of a woman's reproductive system. It is a hollow, pear-shaped organ where a baby grows during pregnancy. The uterus is positioned in the pelvis between the bladder and the rectum.
The narrow, lower portion of the uterus is the cervix. The broad, middle part of the uterus is called the body, and the dome-shaped top of the uterus is called the fundus. The fallopian tubes extend from either side of the top of the uterus to the ovaries.
There are two layers of tissue in the uterus. The inner lining is called the endometrium, and the outer layer is muscle tissue called the myometrium.
In women of childbearing age, the lining of the uterus grows and thickens each month to prepare for pregnancy. If a woman does not become pregnant, the thick, bloody lining flows out of the body through the vagina. This flow is called menstruation, and is often known as a woman’s period.