Vascular Supply And Innervation Of The Corpora Cavernosa

The arterial supply to the corpora cavernosa is usually from the internal pudendal artery via the common penile artery. The three branches of the common penile artery are the cavernosal artery, the dorsal penile artery and the bulbourethral artery. The cavernosal artery, during its course within the corpus cavernosum, gives off helicine arteries that feed the trabecular erectile tissue and sinusoids. The dorsal artery of the penis is responsible for engorgement of the glans penis. Accessory arteries arising form the obturator, vesical, femoral or external iliac arteries may exist. Only on rare occasions are branches of the obturator or vesical arteries the predominant supply to the corpora cavernosa, making vasculogenic erectile dysfunction after RRP uncommon.5,10

The penis receives innervation from both autonomic and somatic pathways. Somatosensory perception from the penile skin, urethra, corpora cavernosa and glans penis is mediated by the dorsal penile nerve. It reaches the sacral spinal cord via the pudendal nerve. Somatomotor penile innervation is also mediated by branches of the pudendal nerve, and is responsible for contraction of the ischiocavernosus muscle during the rigid erection phase and the rhythmic contraction of the bulbocavernosus muscle during ejaculation.5

Penile autonomic innervation is responsible for regulating the tone of the cavernous smooth musculature and the intra-cavernous arteriolar smooth muscle. Relaxation of these muscles results in tumescence. While the penis is in the flaccid state, blood flow is limited by the basal tone of these smooth muscles. This tonic contraction is mediated by sympathetic stimulus from the cavernous nerves. The sympathetic pathway originates from the T10 to L2 spinal segments and travels through the sympathetic chain ganglia to the hypogastric plexus via the splanchnic nerves. The hypogastric plexus divides into two hypogastric nerves at the level of the aortic bifurcation. These two nerves enter the pelvis medial to the internal iliac vessels and deep to the endopelvic fascia. Both the hypogastric nerves and the pelvic continuation of the sympathetic trunks send branches to the pelvic plexus. In humans, the sympathetic fibers that contribute to the cavernosal nerves and regulate erection originate mostly from the tenth to twelfth thoracic spinal cord segments. The parasympathetic neurons of the cavernosal nerves originate from the intermediolateral cell column of the sacral spinal cord and exit through the sacral foramina reaching the pelvic plexus via the pelvic splanchnic nerves (nervi erigentes). Parasympathetic stimulus results in relaxation of the intracavernous arteriolar smooth muscle and engorgement of the corpora cavernosa.5

The pelvic plexus lies in the retroperitoneum on the antero-lateral aspect of the rectum, approximately 5-11 cm from the anal verge, or at the level of the seminal vesicles. The most caudal aspect of the pelvic plexus may extend to the so-called lateral pedicle of the prostate. The branches of the inferior vesical artery that feed the bladder neck and prostate traverse the pelvic plexus at this level. The cavernous nerves leave the most caudal aspect of the pelvic plexus at the level of the base of the prostate and travel within the leaves of the lateral pelvic fascia on the dorsolateral aspect of the prostate.10,11 As the cavernous nerves reach the apex of the prostate, 9-12 mm cranial to the genitourinary diaphragm, there is further branching. The smaller branches travel along the anterolateral aspect of the urethra in close approximation to it while the larger of these branches travel 4-7 mm lateral to the membranous urethra.

Fig. 30.1. Course of cavernous nerves. The endopelvic fascia on the right has been removed exposing the cavernous nerves. Reprinted from Paick et al.,13 Copyright 1993, with permission from Elsevier Science.

Sural Nerve Interposition Graft During Radical Prostatectomy

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