Penis

The penis, part of the external male genitalia, is involved in both sexual reproduction and urination.

Its cylindrical shape has three primary regions — the glans penis, body, and root.

The enlarged tip surrounding the external urethral orifice is called the glans penis or the head.

The loose skin covering the penis forms the prepuce or foreskin, which extends distally along the glans.

The body of the penis is the elongated region with three cylindrical masses of erectile tissue, each enveloped by tunica albuginea.

The paired dorsolateral masses are called the corpora cavernosa, while the corpus spongiosum is the smaller midventral mass.

During sexual arousal, the columns of erectile tissue fill with blood, causing the penis to become rigid and erect. The corpus spongiosum, which surrounds the urethra, ensures it remains open for the passage of semen during ejaculation.

The expanded proximal end of the corpus spongiosum forms the bulb of the penis. In contrast, the separated and tapered portions of the corpora cavernosa form the crura of the penis.

Together, the bulb and crura form the root of the penis, anchoring it to the pelvis.