Full Penis (Transverse Cross-section View) Description
[Continued from above] . . . intercourse and is a duct for the disposal of fluid waste. The penis becomes erect during sexual excitement, because extra blood is pumped into spongy tissues, resulting in enlargement and hardening which allows penetration into the female organ.
The head of the penis is called the glans and is normally covered with a protective, retractable skin or hood. This skin is often cut off at birth, or circumcised, and it is believed that its removal lessens the risk of cancer and bacterial infections. At the center of the penis is a tube that carries urine from the bladder and semen from the prostate gland, called the urethra. During sexual intercourse, reflexes prevent urine from entering this duct and alkaline solutions are produced and secreted to flush out any traces of urine from the urethra before semen is secreted.