SUPPORT OF PELVIC VISCERA
To clarify the relationships of muscles and fasciae in supporting the pelvis, with particular reference to the vagina and internal female genitalia, the uterus, in the accompanying picture, has been elevated upward and backward. The plane chosen for the section (small upper diagram) runs from a point anterior to the body of the uterus down through the anterior vaginal fornix and along the longitudinal axis of the vagina to the perineum. At this level, the large iliac vessels run close to the superior pubic rami which form the lateral pelvic walls. These pubic rami are connected to the ischiopubic rami across the obturator foramen by the obturator membrane, the obturator internus muscle, and the obturator fascia. The broad ligaments begin at the lateral pelvic walls as double reﬂections of the parietal peritoneum, forming large wings, which divide to include the uterus and separate the pelvic cavity into anterior and posterior compartments. They are continuous with the peritoneum of the bladder anteriorly and the rectosigmoid posteriorly. The broad ligaments contain fatty areolar tissue, blood vessels, and nerves, and at their apices invest the round ligaments, which are condensations of smooth muscle and ﬁbrous tissue holding the uterus forward and inserting below and anterior to the fallopian tubes. The left ovary has been lifted up to demonstrate the uteroovarian and infundibulopelvic ligaments, the latter containing the ovarian blood supply. The bladder peritoneal reﬂection has been detached from the uterus, revealing the endopelvic or uterovaginal fascia, which runs laterally to the pelvic wall as the cardinal ligament, and with the associated blood vessels, nerves, and fat forms the parametrium. The uterine arteries and veins extend medially from their origins in the hypogastric vessels to the lateral vaginal fornices. The ureters (cross-sectioned) at this point pass beneath the uterine vessels and then continue in the uterovaginal fascia medially and anteriorly across the upper vagina into the bladder. The close proximity of the ureters to the uterine blood supply and vagina explains why they may easily be injured during hysterectomy and in operations to repair lacerations of the endopelvic fascia.
The pelvic diaphragm is quite thin in cross section, contrasting sharply with its breadth. Although some of the ﬁbers of the levators come directly from the pelvic brim, the main portion of the muscle originates from the tendinous arch formed by a condensation of the fascia of the obturator internus. The levators here are passing around the posterior vagina and enclosing the upper two-thirds of that organ. Below the levators and separated from them laterally by the upward extension of the ischiorectal fossa is the urogenital diaphragm or triangular ligament, containing at this level the deep transverse perineal muscle and the artery of the clitoris. The lower third of the vagina lies superﬁcial to the pelvic diaphragm, and its opening into the vestibule is bounded by the hymen and farther laterally by the vestibular bulb and its covering bulbocavernosus muscle. Close to the ischiopubic rami at the margin of the bony outlet of the pelvis are the crura of the clitoris, covered medially by the ischiocavernosus muscles and the fat pad in the superﬁcial perineal compartment, which is limited below by Colles fascia. The labia (majora and minora) lie superﬁcial to Colles fascia and between the thighs. The muscles and fasciae below the triangular ligament are concerned chieﬂy with coital function and play no part in the support of the pelvic viscera. This plate demonstrates the surgical implications of either the abdominal or vaginal approach to reconstruction of the elaborate supporting framework of the pelvic ﬂoor.