The male organ through which the tubular URETHRA runs from the neck of the URINARY BLADDER to the exterior at the meatus or opening. URINE and SEMEN are discharged along the urethra, which is surrounded by three cylindrical bodies of erectile tissue, two of which (corpora cavernosa) lie adjacent to each other along the upper length of the penis and one (corpus spongiosum) lies beneath them. Normally the penis hangs down in a flaccid state (when its average length is 9.16 cms) in front of the SCROTUM. When a man is sexually aroused the erectile tissue, which is of spongy constituency and well supplied with small blood vessels, becomes engorged with blood (when the penis length averages 13.12 cms). This makes the penis erect and ready for insertion into the woman's vagina in sexual intercourse. The end of the penis, the glans, is covered by a loose fold of skin – the foreskin or PREPUCE – which retracts when the organ is erect. The foreskin is removed when a male is circumcised.

Abnormalities include HYPOSPADIAS, a congenital disorder in which the urethra opens somewhere along the underside of the penis; the condition is repaired surgically. BALANITIS is inflammation of the glans and foreskin. (See also REPRODUCTIVE SYSTEM; EJACULATION; IMPOTENCE; PRIAPISM.)