What is the structure of the uterus?

The uterus exists in the female body, and the role it plays is self-evident. Although women can survive if their uterus is removed, this is a very abnormal survival. For some young women, the reason why they need to protect their uterus is mainly because the uterus is so important for childbirth. So the question is, what is the structure of the uterus?

Uterine shape:

The uterus of an infertile adult is slightly flattened front and back, in an inverted pear shape, about 7-9 cm long and 2-3 cm thick. It is divided into three parts: base, body and neck. The fundus of the uterus is the convex part above the level of the cervix of the fallopian tube; the narrow and cylindrical lower end is the cervix, which is about 2.5-3 cm long in adults and is a common site for tumors; between the fundus and the cervix is ​​the uterine body. The cervix is ​​divided into two parts: the cervicovaginal part that protrudes into the vagina and the supravaginal part above the vagina. The narrow area where the upper end of the cervix meets the uterine body is called the isthmus, which is about 1 cm long. During pregnancy, the isthmus of the uterus gradually stretches and becomes the lower uterine segment; in the late pregnancy, it can be extended to 7-11 cm, and the isthmus wall gradually becomes thinner. Obstetricians often perform cesarean sections here to avoid entering the peritoneal cavity and reduce the chance of infection.

The uterine cavity is divided into two parts: the upper part is inside the uterine body, called the uterine cavity; the lower part is inside the cervix, called the cervical canal. The uterine cavity is an inverted triangle that is flattened front to back, with the upper two ends connected to the fallopian tubes and the tip connected to the stomach and cervix downward. The cervical canal is fusiform, with the lower opening leading to the vagina, called the cervical ostium. The cervix of a nulliparous woman is mostly round; the cervix of a parous woman is transversely fissured, with the front and back edges called the anterior lip and posterior lip respectively. The rear lip is longer and higher in position. In non-pregnant adults, the distance from the cervix to the uterine fundus is about 6-7 cm, the uterine cavity is about 4 cm long, and the widest part is about 2.5-3.5 cm.

The structure of the uterine wall:

The uterine wall is divided into three layers. The outer layer is the serosa, which is the visceral layer of the peritoneum; the middle layer is the thick muscle layer, which is composed of smooth muscle; the inner layer is the mucosa, that is, the endometrium, which undergoes cyclical changes of proliferation and shedding with the menstrual cycle.

Location of the uterus:

The uterus is located in the center of the pelvis, between the bladder and the rectum; the lower part is connected to the vagina, with fallopian tubes and ovaries on both sides. At the end of pregnancy, the fundus of the uterus is located below the plane of the entrance of the small pelvis, facing forward and upward; the lower end of the cervix is ​​slightly above the plane of the ischial spines. When erect, the uterus lies above the bladder. When the bladder is empty, the adult uterus is in a slightly anteversion and anteflexion position. Anteversion means that the entire uterus tilts forward, and an obtuse angle slightly greater than 90 degrees is formed between the long axis of the uterus and the long axis of the vagina. Anteflexion means that the uterine body and cervix are not in a straight line, and there is an obtuse angle of about 170 degrees between the two that opens forward. The uterus has greater mobility, and the fullness of the bladder and rectum can affect the position of the uterus.

Uterine fixation device

The uterus maintains its normal position mainly by the support of ligaments, pelvic diaphragm and urogenital diaphragm, as well as the traction of surrounding connective tissue. If these fixing devices are weak or damaged, it may lead to abnormal position of the uterus and varying degrees of uterine prolapse, with the cervix lower than the plane of the ischial spines. In severe cases, the cervix may protrude out of the vagina.