Three spongy cylinders comprise the human penis; the paired corpora cavernosa runs dorsolaterally and the corpus spongiosum runs ventrally. Incomplete septa between the corpora cavernosa allow for neurovascular communication, allowing the two bodies to function physiologically and pharmacologically as a single unit. The three corporal bodies are enveloped by a dense fascial structure known as the tunica albuginea. The deep fascia (Buck's fascia) ofthe penis surrounds the outside ofthe tunica albuginea and gives off a thin fibrous septum that separates the corpora cavernosa from the corpus spongiosum. Buck's fascia is attached to the perineal membrane proximally; distally, it is tightly attached to the base of glans penis at the coronal sulcus, where it fuses with the end of the corpora. The fascia has a dense structure and is composed of fibers that run longitudinally. It is firmly attached to underlying tunica albuginea and surrounds the deep dorsal vein and the paired dorsal arteries and nerves (see Fig. 1).
Surrounding the deep penile fascia is the superficial (Colles') fascia, which is continuous with Scarpa's fascia of the lower abdominal wall and with dartos fascia of the scrotum (14). This fascia is surrounded by skin. The fundiform ligament is the thickening of Colles' fascia, which continues to join the linea alba and splits to surround the body of the penis and then fuses with the septa of the scrotum. Deep to Colles' fascia is the triangular suspensory ligament, which is in continuity with Buck's fascia; its attachment to the pubic bone maintains penile position during erection (see Fig. 2).
The proximal penis is anchored to the inferior pubic rami and consists of the crura of the corpora cavernosa. The bulbospongiosus muscle surrounds the penile bulb (supplied by the deep branch of the perineal nerve). The ischiocavernosus muscles (supplied by the perineal branch of the pudendal nerve) cover the penile crura and proximal part of the penile shaft. These skeletal muscles lie between Colles' and Buck's fascia. The glans penis appears to be spongelike because of a rich venous plexus. It has no fibrous sheath, and it is covered with very thin and firmly adherent skin. A useful mnemonic for the penile layers is ABCD: A = albuginea, B = Buck's fascia, C = Colles' fascia, and D = dermis.
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