Blood Supply of Perineum
The internal pudendal artery, after emerging from the Alcock canal, gives off several branches. One, the perineal artery, passes beneath the Colles fascia in the perineum to course forward anteriorly, either under or over the superﬁcial transverse perineal muscle. This vessel supplies the superﬁcial structures of the urogenital diaphragm and sends a small branch, usually transversely, across the perineum (transverse perineal artery) that anastomoses with the artery from the opposite side. The perineal artery then continues anteriorly underneath the pubic arch and supplies both the ischiocavernosus and bulbospongiosus muscles. It also sends branches to the posterior scrotal surface.
The deep terminal branch of the internal pudendal artery pierces the inferior layers of the urogenital diaphragm and continues forward in the cleft between the ischiocavernosus and bulbospongiosus muscles, where it divides into the dorsal artery and the cavernous artery of the penis. As it courses between the inferior and superior layers of the fasciae of the urogenital diaphragm, it supplies the bulbous portion of the urethra and the corpus spongiosum. Distal to the bulbar urethra, a small branch passes downward through the inferior fascial layer of the urogenital diaphragm and enters the corpus spongiosum, where it continues to the glans penis (urethral artery).
The deep or cavernous artery of the penis pierces the inferior layer of the urogenital diaphragm, enters the crus penis obliquely on each side, and continues distally in the center of the corpus cavernosum of the penis. The blood ﬂow within this artery is commonly measured by ultrasound in the evaluation of arterial erectile dysfunction. The dorsal artery of the penis pierces the inferior fascia of the urogenital diaphragm, just below the transverse ligament of the pelvis (see Plate 2-5), after which it traverses the suspensory ligament of the penis and courses forward on the dorsum of the penis beneath Buck fascia, where it terminates in the prepuce and glans penis. The paired dorsal arteries of the penis are situated between a single deep dorsal vein and paired dorsal nerves. The dorsal artery sends branches downward through the tunica albuginea of the penis into the corpus cavernosum, where they anastomose with the ramiﬁcations of the cavernous artery.
In general, the arteries supplying the internal and external genitalia are accompanied by similarly named veins. The dorsal veins of the penis, however, pursue a different course. The subcutaneous dorsal (median and lateral) veins, which receive tributaries from preputial veins, pass proximal to the symphysis pubis, where they terminate in the superﬁcial external pudendal veins that drain into the femoral veins. The single deep dorsal vein of the penis originates in the sulcus behind the glans penis and drains the glans and the corpus spongiosum. It courses posteriorly in a sulcus between the right and left corpora and passes between both of the two layers of the suspensory ligament at the penile base (see Plate 2-6). It then passes through an aperture between the arcuate ligament of the pubis and the anterior border of the transverse pelvic ligament (see Plate 2-5). The deep dorsal vein then divides into branches that join the prostatic venous plexus. This plexus of thin-walled veins, with similar veins from the bladder and rectum, communicate freely with one another and with adjacent venous tributaries. Ultimately, they empty into the internal iliac veins.