Your penis: the lowdown

The glans, or head, of the penis is covered with very thin skin that contains numerous nerve-endings and is therefore very sensitive to touch.

The glans, or head, of the penis is covered with very thin skin that contains numerous nerve-endings and is therefore very sensitive to touch. At birth the foreskin covers the glans and on its lower side it is tethered to the inner surface by the frenulum. The frenulum is the small piece of skin on the underside of the penis where the glans meets the shaft. It is also a very sensitive area.

The foreskin may be removed in a procedure known as circumcision. Circumcision is usually performed at a young age, for religious or hygiene reasons. The skin of the penis is thin and stretchy and loosely attached to the underlying tissues.

The penis itself is composed of erectile tissue and is richly supplied with sensory nerves. It is filled with a rich network of blood vessels and three cylindrical areas of spongy tissue. The spongy tissue remains empty when the penis is flaccid and it fills during erection.

The Scrotum
The scrotum is the pouch of skin at the root of the penis that holds the testes. For healthy sperm to be produced the testes need to be kept at a temperature lower than the rest of the body. Under the skin of the scrotum is a muscle that contracts in response to cold or exercise, in order to maintain the ideal temperature.

INTERNAL VIEW
The Testicles
The testicles have two functions:

• To produce sperm
• To produce male hormones, primarily testosterone.
• Production of sperm continues throughout a man's life, unless there is a problem with infertility.

The Epididymis
When the sperm have been produced they move to a large tube called the Epididymis, where they continue to mature for six weeks.

The Vas Deferens
The Vas Deferens are the tubes that carry sperm from the Epididymis to the urethra and penis.

The Bladder
The bladder holds urine. There is a valve at the base of the bladder that closes when the penis is erect to prevent urination.

The Seminal Vesicles
The seminal vesicles produce and store semen. The sperm are supported and nourished by this sticky fluid that forms part of the ejaculate.

The Prostate Gland
The prostate gland is situated just below the neck of the bladder. It produces secretions that form part of the seminal fluid during ejaculation, and pushes the ejaculate (semen and sperm) out of the penis when the man has an orgasm.

The Cowpers' Gland
These glands are on either side of the urethra. They contain a clear alkaline fluid that cleans the urethra of any urine before ejaculation. This fluid also acts as a lubricant. This fluid is called pre-ejaculate (pre-cum) but may also contain a few sperm.

The Urethra
The urethra is the tube that runs from the bladder and seminal vesicles to the opening at the head of the penis. Semen, urine and pre-ejaculate pass down the urethra.