The uterus is a hollow muscular organ that, along with the ovaries, the fallopian tubes (or uterine tubes), the vagina and the vulva form the female reproductive tract. The body is charged to receive the fertilized egg, to allow its development and to expel the foetus when the pregnancy comes to an end. The uterus receives the outlet of the fallopian tubes and at the bottom it opens into the vaginal cavity.
The structure of the uterus may be different in each woman: this organ undergoes multiple changes through life according to different stages of sexual development in women (prepuberty, puberty, sexual maturity, menopause), in cases of pregnancy and during the menstrual cycle.
What is the uterus?
The shape of the uterus reminds roughly of that of a cone with the tip pointing down. In women who have not had children, the size of the uterus is around 6-7 centimetres long, 4.3 centimetres wide and 3.2 centimetres thick with a total weight of about 50 grams; however, these values can change considerably in women who have had several children. In this case, size and weight of the uterus may increase.
The anatomy of the uterus includes three tissue layers:
- the inner layer: it is also known as endometrium and it is the most active uterine layer that responds to cyclic ovarian hormone changes. This layer is essential to menstrual and reproductive functions.
- the middle layer: the middle layer is known as the myometrium or muscular layer, which makes up most of the uterine volume and it is composed of smooth muscle cells.
- the outer layer: the serosa or perimetrium is the thin outer layer of tissue that is comprised of epithelial cells that envelop the uterus.
The uterine cavity is lined by the endometrium, thanks to which the nourishment of the embryo in the first period of intrauterine life is guaranteed. The muscle that lines the uterus (myometrium) is thick and firm and the contractions at birth enable the delivery of the foetus.
There are two portions in which it is possible to ideally divide the uterus:
- a larger part – called uterine body or the body of the uterus – which expands upwards and in which flow the fallopian tubes (or uterine tubes);
- a narrower part, called the neck of the uterus or cervix, a cylindrical-like form that is facing downwards and expands to fit into the vagina.
Before puberty the cervix corresponds to about half of the total length of the uterus; however, in women who have had children the cervix becomes one third of the entire length of the organ: this occurs especially in women who have had more children, following the remarkable development of the uterine body to host pregnancies.
Appropriate blood flow to the uterus is provided through the ovarian and uterine arteries. The uterine arteries are a part of the anterior divisions of the iliac artery. Sometimes the uterine artery provides blood flow to the vaginal artery, which supplies the upper vagina and the arcuate arteries that surround the uterus.
What function does the uterus serve?
The function of the uterus is threefold: it welcomes the fertilized egg, it enables development, and allows the expulsion of the foetus when the pregnancy comes to an end.
