The anatomy of the penis is highly complex. It is basically comprised of two cylinders of sponge-like vascular tissue called Corpus Cavernosa that fill with blood to create an erection. Blood is pumped into the penis under pressure and a series of valves keep it in the penis to maintain the erection. A third cylinder is the urethra, a tube that carries the urine and the ejaculation fluid. Blood flows to the penis by two very small arteries that come from the aorta in the heart. The head of the penis is called the Glans.

When the blood vessels become blocked and no blood can get to the penis, impotence can occur. Another major problem is leakage of blood from the penis into the veins around the penis known as a venous leak. This is a common problem which requires more blood to be pumped into the penis in order to keep it hard.

Vas Deferens:

The erectile tissue (Corpora Cavernosa & Corpus Spongiosum) in the penis expands during sexual stimulation. This can either be visual, tactile, auditory, olfactory or imaginative. During sexual stimulation the arteries supplying the penis with blood dilate and large amounts of blood rush into the erectile tissue. The blood then becomes trapped causing the penis to stay this way until ejaculation or until the male is no longer stimulated.

Epididymus:

Epididymis is a structure which lies on and around each testicle. It functions in the transport, storage and maturation of sperm cells originating from the testicle. When a man complains of scrotal pain, acute or chronic epididymitis is far and away that most common diagnosis.

Acute epididymitis is usually more severe involving more significant swelling and pain than chronic epididymitis. Epididymitis which lasts more than six weeks is considered chronic epididymitis.

Testes:

Testes are a large number of tightly packed coiled tubes. This is where sperm is produced. Sperm production takes about two months, but it's a continuous cycle. A typical male produces several hundred million each day. This sperm production process is called Spermatogenesis. Sperm that is not ejaculated is then broken down and reabsorbed by the body.

Testes also contain cells that secrete the male sex hormone testosterone. Spermatozoa are among the smallest and most highly specialized cells in the body. All the genetic material that is transmitted from a father to its baby is found in each sperm head. The nucleus is covered by a specialized enzyme coating that enable the sperm to break down the covering of the egg and permit entry should contact occur. Each sperm has a mid-piece and an elongated tail that helps it swim in its quest to fertilize the closest female egg.

Scrotum:

The scrotum is a pouch-like sac that hangs on the external part of the body cavity behind the penis. This is where the testicles are contained. This location provides the correct temperature for the sperm to be produced.