Uteri

Uteri is the Latin plural of uterus and is used in anatomical contexts to refer to the uterus as a single organ or to multiple uteri across species. In humans, there is typically a single uterus, though congenital uterine anomalies can produce two uterine cavities or a didelphic uterus in some individuals. The term is common in scientific writing and in comparative anatomy.

Anatomy and structure

The uterus is a pear-shaped muscular organ in the female pelvis, positioned between the bladder and the rectum. It comprises the fundus at the top, the body (corpus), the narrow isthmus, and the cervix opening into the vagina. The wall has three layers: the perimetrium (outer serosa), the myometrium (thick smooth muscle), and the endometrium (inner lining with functional and basal layers). The endometrium undergoes cyclic changes in response to hormonal signals. Support comes from ligaments such as the broad ligament, round ligaments, cardinal ligaments, and uterosacral ligaments. Blood supply is via the uterine arteries from the internal iliac arteries; venous drainage follows a parallel path, with lymphatic drainage to pelvic nodes.

Function

In the nonpregnant state, the endometrium thickens and is shed during menstruation if fertilization has not occurred. If implantation occurs, the uterus accommodates the developing embryo and supports placental function. During labor, the myometrium contracts to expel the fetus, aided by cervical dilation.

Development and variation

The uterus develops from the Müllerian ducts during embryogenesis. Variants include septate, bicornuate, unicornuate, or didelphic uteri, reflecting differing degrees of duct fusion. In many mammals, uteri may be paired (duplex or bicornuate), whereas humans typically have a simplex uterus with a single uterine cavity.