The cervix is a part of the uterus, the part that is lowest, below the fundus of the uterus, and dipping into the vagina. During childbirth to allow for the passage of the baby. It also allows the passage of menstrual fluid from the uterus, and sperm needs to travel through the cervix in order to reach the uterus.
Despite the variety of objects passing through the cervix, it is only approximately two inches long, and is tubular in shape.