Male sexual arousal is a complex process involving the brain, hormones, emotions, nerves, muscles and blood vessels. If something affects any of these systems — or the delicate balance among them — erectile dysfunction can result.
Anatomy of an erection
The penis contains two cylindrical, sponge-like structures (corpus cavernosum) that run along its length, parallel to the tube that carries semen and urine (urethra).
When a man becomes sexually aroused, nerve impulses cause the blood flow to the cylinders to increase several times the normal amount. This sudden influx of blood expands the sponge-like structures and produces an erection by straightening and stiffening the penis.
Continued sexual arousal maintains the higher rate of blood flow into the penis and limits the blood flow out of the penis, keeping the penis firm. After ejaculation or when the sexual excitement passes, the excess blood drains out of the spongy tissue, and the penis returns to its nonerect size and shape.
Tags: Erectile dysfunction