broad ligament

The broad ligament is a double-layered fold of peritoneum extending from the lateral sides of the uterus to the pelvic walls. It functions as a mesentery for the internal female genital organs and is divided into three parts: the mesometrium (surrounding the uterus and forming the majority of the broad ligament), the mesosalpinx (suspending the fallopian tubes, located superiorly), and the mesovarium (suspending the ovaries posteriorly). Importantly, the ovaries themselves are not covered by peritoneum, distinguishing them from the tubes and uterus which are intraperitoneal structures covered by the mesosalpinx and mesometrium respectively.

Structures traveling within the broad ligament include the uterine tubes, round ligament of the uterus, ovarian ligament, uterine and ovarian blood vessels (uterine artery running within the base near the cardinal ligament), lymphatics, and autonomic nerves. The ureter passes close to the base of the broad ligament, beneath the uterine artery ("water under the bridge"), which is clinically significant during hysterectomy as the ureter is at risk of injury when the uterine artery is ligated.

Embryologically, the broad ligament forms from the fusion of the paramesonephric (Müllerian) ducts as they descend and fuse in the midline, with the peritoneum draping over them.

Clinical relevance: Broad ligament is a common site for ectopic pregnancy (broad ligament pregnancy), fibroids can extend into it (intraligamentary fibroids), and it can be involved in pelvic masses or endometriosis. Understanding its relationship to the ureter is critical for pelvic surgery to avoid iatrogenic ureteral injury.