wombs

The womb, or uterus, is a pear-shaped muscular organ in female mammals in which a fertilized egg implants and a fetus develops during pregnancy. In humans it sits in the pelvis between the bladder and the rectum. The organ is surrounded by supporting ligaments and connected to the vagina via the cervix.

The uterus has three main parts: the fundus at the top, the central body (corpus), and the cervix at the lower end. It consists of three layers: the outer perimetrium (serosa), the thick middle myometrium (smooth muscle), and the inner endometrium lining that thickens during the menstrual cycle and is shed if pregnancy does not occur.

During puberty, hormonal cycles regulate endometrial thickening and shedding. If a sperm fertilizes an egg, the embryo implants into the endometrium and pregnancy proceeds with placental support. The myometrium contracts during labor to help birth; the cervix effaces and dilates. The uterus is supplied by uterine arteries and drained by uterine veins; innervation comes from pelvic nerves.

Congenital uterine anomalies include bicornuate, unicornuate, didelphys, or septate uteri, which can influence fertility and pregnancy outcomes. Common conditions affecting the uterus include fibroids (leiomyomas), adenomyosis, and endometriosis. Ectopic pregnancy most often occurs in the fallopian tubes and is a medical emergency.

Evolutionarily, the uterus supports viviparous reproduction in many mammals and can vary in structure across species; in humans, it typically supports a single fetus with a placenta forming a decidual interface.