The human penis is composed of the paired dorsal corpora cavernosa and the ventrally placed corpus spongiosum. The corpus spongiosum contains the urethra and is contiguous with the glans penis distally. Each corpus is surrounded by a fibrous sheath, the tunica albuginea. Between the two corpora cavernosa is an incomplete perforated septum allowing them to function in unison.

Surrounding all three corpora is an additional fibrous layer, Buck’s fascia. Superficial to Buck’s fascia is Colles’ fascia extending from the base of the glans to the urogenital diaphragm where it is contiguous with Scarpa’s fascia.

Superficial to Colles’ fascia is the skin.
Proximally, the corpora cavernosa form the penile crura, which are anchored to the pubic rami and are covered by the ischiocavernosus muscles. The proximal corpus spongiosum forms the penile bulb, which is enveloped in the bulbospongiosus muscle. The suspensory ligament of the penis arises from the linea alba and pubic symphysis and inserts on the tunica albuginea to support the pendulous portion of the penis.

Corpora The corpora cavernosa are two spongy cylinders comprised primarily of arterial sinusoids and smooth muscle surrounded by the tunica albuginea. The cavernosal tunica albuginea is 2–3 mm thick in the flaccid state and is composed mostly of collagen fibers with a smaller portion being elastic fibers. The cavernosal tunica has an inner circular layer and an outer longitudinal layer of fibers. The histologic appearance of corpus spongiosum is similar to the corpora cavernosa and it contains larger sinusoids. Additionally, the tunica albuginea surrounding this corpus is thinner, has only one circular fiber layer, and contains more elastic fibers.

Glans The glans forms the distal portion of the penis. It is contiguous with the corpus spongiosum. It is covered with very thin, firmly adherent skin. Additionally, the tunica on the glans albuginea is absent.