The uterus is one of the female internal reproductive organs; it is a hollow, muscular organ located in the center of the pelvis. In front is the bladder, behind is the rectum, and below is connected to the vagina, flanked by the fallopian tubes and ovaries. The shape of the uterus is a triangle with a wide top and a narrow bottom, like an inverted pear, with a flat front and a slightly protruding back. 7-8 cm long, 4-5 cm wide and 2-3 cm thick, the protruding part of the uterus is the uterine fundus, the wider part above is the uterine body, and the narrower cylindrical part below is the cervix. In adult women, the ratio of uterine body to cervix is 2:1. The wall of uterus is plasma layer, muscle layer and mucosa layer from outside to inside in order.