The uterus is a hollow organ, located in the center of the pelvic cavity, in an inverted pear shape, such as the size of an egg. The upper part of the uterus is wide, and it is called the uterine body. The upper part of the uterus is called the uterine bottom, and the two sides of the uterine bottom are uterine horns, which communicate with the fallopian tube. The lower part of the uterus is narrow and cylindrical, and it is called the cervix. The uterine cavity is covered with mucosa, which is called the endometrium. After puberty, the endometrium changes periodically and produces menstruation under the influence of ovarian hormones. The uterus is the channel for sperm to reach the fallopian tube. It is the place where embryos grow and develop. Uterus dysplasia or malformation all affect fertility. The uterus can be divided into Fundus, Body, Isthmus and Cervix from top to bottom: fundus: the part above the horizontal line of fallopian tubes. Uterus: The thinner part in the middle of the uterus. Isthmus: the part connecting the uterine body with the cervix. The length is only 1 cm. Cervix: A narrow opening at the base of the uterus. Connect the vagina. Looking at the uterus from the back, the uterus is fixed by eight ligaments: two main ligaments of the uterus: one front and one back. The main ligament contains smooth muscle, blood vessels and nerves. It is the main ligament to maintain the normal position of the uterus and prevent it from falling into the vagina. Two broad uterine ligaments: located on both sides of the uterus. Connect the uterus and pelvis. Broad ligament covers the outer membrane of uterus and the ligament connecting uterus with ovary. Two round ligaments of uterus: keep the uterus slightly tilted and bent forward. Two uterine fundus ligaments: located on both sides of the rectum. Connect the uterus to the bone. The uterus can be divided into three layers from outside to inside: tunica uteri, myometrium and endometrium. There is an outer lining around the uterus, called the outer membrane of the uterus, which is a part of the peritoneum and does not cover the whole uterus. The uterus is mostly composed of muscles, called myometrium. These muscles are smooth muscles. The innermost layer of the myometrium is the junctional zone, which is also the thickened part of adenomyosis.