Corpora Cavernosa: Keep the Love Tunnels Open
This spongy erectile tissue in both male and female genitalia (see clitoris) becomes engorged with blood during sexual arousal. In men, this engorging is responsible for the erect penis.
Think of a double-barreled shotgun with a sight going all the way to the muzzle. The barrels are the corpora cavernosa, and the sight is the corpus spongiosum (which houses the urethra.) During arousal, the barrels rapidly fill with blood, and just as quickly, neurotransmitters from the brain relax the set of muscles which ordinarily limit blood flow to the penis. Voila! An erection. Then, the penis' outer sheath contracts to trap the blood. An erection with staying power!
Viagra, whose active ingredient is a neurotransmitter discovered during research on heart disease, works by helping to keep the blood trapped in the penis. It's only one of about a half-dozen sex-enhancing drugs in the pipelines of the big pharmaceutical houses.
For both sexes, the health of the circulatory system is critical to the proper functioning of this erectile tissue. Exercise! Exercise! Exercise! And you'll preserve your sexual health for many years.