The uterus is the organ that nurtures the embryo, fetus and produces menstruation. The uterus is a luminal muscular organ, slightly flattened inverted pear-shaped, weighing about 50 g. The upper part of the uterus is called the uterine body, the upper part is called the uterine fundus, the uterine fundus is flanked by the uterine horns and the fallopian tubes, and the lower part of the uterus is narrower and cylindrical called the cervix. The ratio of the uterine body to the cervix varies with age, from 1:2 in infancy to 2:1 in adult women and 1:1 in the elderly, and the uterine cavity is a triangle with a wide upper and narrow lower cavity, with the fallopian tubes on both sides and the cervical canal at the tip. The narrowest part between the uterine body and the cervix is called the isthmus of the uterus. The uterus is located in the center of the pelvis, between the bladder and the rectum, with the lower end connected to the vagina and the fallopian tubes and ovaries on either side. When the bladder is empty, the normal position of the adult uterus is mildly anteverted and flexed, mainly by the uterine ligaments and the support of the pelvic floor muscles and fascia, with the lower end of the cervix at the level of the sciatic spine under normal conditions.