Anatomy and blood supply of the urethra and penis

Abstract

The penis is made up of three cylindrical erectile bodies. The pendulous anterior portion hangs from the lower anterior surface of the symphysis pubis. The two dorsolateral corpora cavernosa are fused together, with an incomplete septum dividing them. The third and smaller corpus spongiosum lies in the ventral groove between the corpora cavernosa, and is traversed by the centrally placed urethra. Its distal end is expanded into a conical glans, which is folded dorsally and proximally to cover the ends of the corpora cavernosa and ends in a prominent ridge, the corona. The corona passes laterally and then curves distally to meet in a V ventrally and anterior to the frenulum, a fold of skin just proximal to the external urethral meatus. The erectile tissue of the corpora cavernosa is made up of blood spaces lined by endothelium enclosed in a tough fibroelastic covering, the tunica albuginea. The corpus spongiosum is smaller with a much thinner tunica albuginea, and its erectile tissue surrounds the urethra. Proximally, at the base of the pendulous penis, the corpora cavernosa separate to become the crura, which are attached to the inferomedial margins of the pubic arch and adjoining inferior surface of the urogenital diaphragm. The corpus spongiosum becomes expanded into the bulb, which is adherent in the midline to the inferior surface of the urogenital diaphragm. This is the fixed part of the penis, and is known as the root of the penis. The urethra runs in the dorsal part of the bulb and makes an almost right-angled bend to pass superiorly through the urogenital diaphragm to become the membranous urethra.