Human Uterus

The human uterus is an unpaired hollow organ, which is composed of smooth muscles. It lies in the central portion of the cavity of the true pelvis, between the pubic symphysis and sacrum. This pear-shaped organ is an essential part of the feminine reproductive system, where the embryo and fetus develop and get nourished. Its upper portion is the widest part, while its lower section is narrowest part, which faces downwards and forwards. The top of the uterus is called the fundus, while the bottom is the cervix (neck), which fans out a little before continuing with the vagina.

Size and Weight

The shape and size of the uterus change considerably during the different periods of life, particularly in connection with pregnancy. It measures approximately 7 cm in length in a nulliparous woman (who has never borne a child), and about 9 cm in length in a woman who has borne children. Meanwhile, the cavity of the uterus is about 6 cm in length. It is 5 cm wide at the level of the fundus at the top. Its weight varies from 30 to 100 g.

Structure

The wall of the uterus consists of three layers of tissues; the outer serous coat (perimetrium), the middle muscular coat (myometrium), and the inner mucous coat (endometrium). The perimetrium is a direct continuation of the serous coat of the urinary bladder, being fused with the myometrium for a long distance on the anterior and posterior surfaces, as well as on the fundus. The muscular coat, myometrium, is the thickest and strongest layer and it is composed of smooth muscle fibers with a mixture of connective tissue and elastic fibers.

The mucous coat of the uterus (endometrium) is fused with the muscular coat, forming the lining of the cavity. It consists of a single-layer columnar ciliated epithelium, containing tubular uterine glands. All three layers receive oxygenated blood from small branches from the uterine artery, which arises from the internal iliac.

Below, longitudinal section of human uterus.