The penis is the male reproductive organ and it is the last part of the urinary tract. It consists of three bodies in cylindrical form covered by the end glans: this is a two corpora cavernous side and a central spongy body, crossed by the urethra.


What is the penis?

The penis reaches full development and growth during puberty. Moreover, the penis is constituted from several parts, such as the glans (head or tip of the penis), the corpus cavernosum (two tissue columns that run along the sides of the penis), the corpus spongiosum (a sponge-like tissue column that runs along the front of the penis) and the urethra (the tube that carries urine from the bladder to the urethral opening).

At the height of the glans opens the urethral meatus, or orifice of urethra that allows the passage of sperm and urine to the outside of the body. In general, the glans is partially covered by a fold formed from the skin of the penis, called foreskin. The skin of the penis is continuous with that of the lower abdominal wall. The distal penile skin is confluent with the smooth skin that covers the glans. At the corona, the skin folds to form the foreskin that covers the glans.

Both cavernous corpora are crossed by deep arteries of the penis (cavernous arteries) and each is enclosed by tunica albuginea, a very inelastic fascial structure. Together, the two cavernous corpora are surrounded by a tough fibrous coating, called the "Buck's fascia." The innervation of the penis is very complex and comes from the sacral plexus through the pudendal nerve and the sacral plexus through the cavernous nerves.

The cavernous corpora are formed by erectile tissue constituted in turn by many vascular spaces of irregular shape. When the penis is at rest, there is a reduced amount of blood flow in the vascular spaces; however, during erection the amount of blood that flows in the corpus cavernosum greatly increases and so does the pressure exerted by the blood against the almost inelastic tunica albuginea. A complex mechanism that relies on increasing the blood supply and the related reduction in its flow determines the achievement of penile rigidity.

Blood supply to the penile skin is provided from the left and right superficial external pudendal arteries, which extend from the femoral artery. These arteries branch out into dorsolateral and ventrolateral branches, which extend across the midline forming an extensive subdermal vascular plexus.

The nerves to the penis come from the pudendal and cavernous nerves. The pudendal nerves supply somatic motor and sensory innervation to the penis. On the other hand, the cavernous nerves provide nerve supply to the erectile tissue.


What function does the penis serve?

There are two main functions essentially performed by the penis: the sexual function and the urinary function. Sexual function is facilitated through the characteristics of the corpora cavernosa, which is reached by many blood vessels and able to fill with blood during erection, which in turn enables the realization of sexual intercourse. On the other hand, the urinary function is instead maintained from the urethra and urethral meatus.