The uterus is the internal organ of the female reproductive system located in the lower pelvic cavity. It contains a rich blood supply and reacts to hormonal changes monthly resulting in menstruation. During pregnancy, the lining of the uterus remains inside the body to nourish the unborn child rather than menstruating. The uterus is divided into three regions and connected to the ovaries by fallopian tubes which transport eggs from the ovaries to the uterus.