Uterus
Organ for embryonic and fetal development in female mammals.
The uterus (from Latin uterus, pl.: uteri or uteruses) or womb is the organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic and fetal development of one or more fertilized eggs until birth. It is a hormone-responsive sex organ that contains glands in its lining that secrete uterine milk for embryonic nourishment. The term uterus is also applied to analogous structures in some non-mammalian animals.
- location
- Pelvic region, behind and overlying the bladder, in front of the sigmoid colon
- size
- About 7.6 cm long, 4.5 cm broad, 3.0 cm thick
- weight
- About 60 grams in a typical adult
- layers
- Endometrium, myometrium, perimetrium
- position
- Anteverted in 50% of women, retroverted in 25%, midposed in 25%
- blood supply
- Uterine artery and ovarian artery
Lore & Background
In humans, the uterus is located within the pelvic region immediately behind and almost overlying the bladder, and in front of the sigmoid colon. It is pear-shaped and about 7.6 cm long, 4.5 cm broad, and 3.0 cm thick, weighing about 60 grams. Anatomically, it can be divided into four regions: the fundus, body, cervix, and cervical canal. The cervix protrudes into the vagina. The uterus is held in position by ligaments, including the pubocervical, cardinal, and uterosacral ligaments, and is covered by the broad ligament of peritoneum.
Reader's Guide
The uterus has three layers: the endometrium, myometrium, and perimetrium. The endometrium is the inner epithelial layer with a basal and functional layer; the functional layer thickens and is shed during the menstrual or estrous cycle. During pregnancy, uterine glands and blood vessels increase in size and form the decidua, and vascular spaces fuse to form the placenta. The myometrium consists mostly of smooth muscle, and the perimetrium is a serous layer of visceral peritoneum. The uterus is primarily supported by the pelvic diaphragm, perineal body, and urogenital diaphragm, and secondarily by ligaments. Its primary reproductive function is to prepare for implantation of a zygote and maintain pregnancy; in the absence of pregnancy, menstruation occurs. The uterus develops from the paramesonephric ducts, which fuse into a simplex uterus in humans, though other animals may have a duplex uterus. Clinical significance includes assessment of fetal growth by measuring fundal height, and pathological states such as retroversion, prolapse, and accumulation of fluids.
Did You Know?
- The uterus is also called the womb, from Germanic origin, commonly used in everyday contexts.
- In humans, the uterus is normally in anteversion and anteflexion, but can be retroverted in 25% of women.
- The endometrium has a functional layer that is shed during menstruation if no pregnancy occurs.
- The uterus develops from the paramesonephric ducts, which fuse into a single organ in humans.
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