BLOOD SUPPLY OF PERINEUM
The perineum and vulva are richly supplied with blood vessels, which become clinically signiﬁcant during childbirth and surgical procedures. Blunt trauma to the area, such as straddle injuries in children, can result in signiﬁcant bleeding or hematoma formation when vessels are ruptured and bleeding into the loose compartments of the perineum occurs.
The internal pudendal artery in the female is a far smaller vessel than it is in the male, though its course is generally the same in both sexes. When leaving the lesser pelvis through the lower part of the greater sciatic foramen, it enters the ischiorectal fossa through the lesser sciatic foramen. Here, accompanied by its venae comites and the pudendal nerve, it lies in a ﬁbrous canal (Alcock canal) formed by the fascia covering the obturator internus muscle. The branches of the internal pudendal artery include small ones to the gluteal region, the inferior hemorrhoidal artery, the perineal artery, and the artery of the clitoris. The pudendal artery (and vein) is closely associated with the pudendal nerve as it passes the ischial spine near the insertion of the sacrospinous ligament (on the dorsal aspect of the coccygeal muscle), placing it at risk when sacrospinous colpopexy is performed. (A rare complication of this operation is massive hemorrhage from the inferior gluteal or pudendal arteries.)
The inferior hemorrhoidal artery pierces the wall of Alcock canal and passes medially through the ischiorectal fat to supply the anal canal, anus, and perineal area. The perineal artery pierces the base of the urogenital diaphragm to enter the superﬁcial perineal compartment, where it supplies the ischiocavernosus, bulbocavernosus, and transverse perineal muscles. A constant transverse perineal branch runs along the superﬁcial transverse perineal muscle to the central point of the perineum. The terminal branches of the perineal artery, the posterior labial arteries, pierce the deep layer of the superﬁcial perineal fascia (Colles fascia) to the labia.
The artery of the clitoris enters the deep compartment of the urogenital diaphragm and runs along the inferior ramus of the pubis in the substance of the deep transverse perineal muscle and the sphincter of the membranous urethra, ending in four branches, which supply chieﬂy the erectile tissue of the superﬁcial perineal compartment. The artery of the bulb passes through the inferior fascia of the urogenital diaphragm to supply the cavernous tissue of the vestibular bulb and the Bartholin gland. The urethral artery runs medial- ward toward the urethra and anastomoses with branches from the artery of the bulb. The deep artery of the clitoris pierces the fascial ﬂoor of the deep compartment just medial to the corpus cavernosum of the clitoris, which it enters. The dorsal artery of the clitoris leaves the deep perineal compartment just behind the transverse pelvic muscle and runs over the dorsum of the clitoris to the glans.
The blood supply of the vulva and perineum is richly connected to the vascular supply of the entire vaginal barrel, the cervix, and the uterus through a number of ascending and descending anastomoses. This vascular net surrounds the vaginal canal, with major trunks running in the lateral vaginal wall at the 3- and 9-o’clock locations. Trauma to these areas, as with a vaginal delivery, can result in signiﬁcant blood loss that may be difﬁcult to control.