uteruses

The uterus is a hollow, muscular organ of the female pelvis that houses and nourishes the developing embryo and fetus. It consists of the fundus (the top), the body (corpus), and the cervix at its lower end, with a cavity lined by endometrium. The thick muscular wall is the myometrium, and the outer surface is covered by peritoneum (the perimetrium). Most individuals have a uterus that is anteverted and anteflexed in the pelvis.

During embryonic development, the uterus forms from paired Müllerian ducts. Incomplete fusion or resorption can produce several uterine anomalies, including uterus didelphys (double uterus with two cervices), bicornuate uterus (two uterine horns with a single cervix), unicornuate uterus (one horn, sometimes with a rudimentary horn), and septate or arcuate variants. These conditions can affect menstruation, fertility, and pregnancy outcomes and may be identified on imaging.

The endometrium responds to ovarian hormones, thickening in the proliferative and secretory phases in preparation for implantation. If fertilization does not occur, the functional layer is shed during menstruation. The myometrium contracts during labor to aid childbirth, and the cervix serves as a canal and a barrier, with mucus properties that change around ovulation.

Arterial supply comes mainly from the uterine arteries, branches of the internal iliac arteries, with collateral supply from the ovarian arteries. Venous drainage runs to the uterine venous plexus and then to the internal iliac veins. Lymphatics drain to para-aortic, external iliac, and internal iliac nodes; autonomic nerves from the pelvic plexus provide innervation.

Common uterine conditions include leiomyomas (fibroids) in the myometrium and adenomyosis, where endometrial tissue resides within the myometrium. Endometrial hyperplasia and gynecologic cancers can occur with age and hormonal changes. Congenital anomalies and uterine health impact fertility and obstetric risk, including miscarriage and preterm birth.