Understanding erectile dysfunction requires a basic knowledge of penis anatomy and the complex process of creating and sustaining an erection. An erection doesn’t just happen: it requires nerve impulses, muscles, and blood vessels to all work together. Interrupting the process at any stage can cause impotence. Penis anatomy is remarkably complex: the information on this page provides definitions for the most important parts.
The Corpora Cavernosa
The corpora cavernosa are two chambers that fill most of the penis. The chambers are filled with a spongy tissue that includes muscles, open spaces, veins and arteries. An erection occurs when the corpora cavernosa become engorged with blood and expand.
The Tunica Albuginea
A membrane called the tunica albuginea surrounds the corpora cavenosa. This membrane helps keep blood in the penis during an erection.
The urethra is the tube through which urine travels. Ejaculate also travels through the urethra. It runs down the underside of the penis, beneath the corpora cavernosa and widens at its opening, called the meatus. The meatus is located at the glans (the head of the penis).
The corpus spongiosum is a chamber that surrounds the urethra. It becomes engorged with blood during an erection.
The prostate is a small gland located in the pelvis. It surrounds the urethra and plays an important role in ejaculation. Sperm, which is produced in the testicles and stored in the seminal vesicles, is mixed with prostatic fluid and secretions from the bulbourethral gland to form semen. During ejaculation, semen is expelled through the urethra from the ejaculatory ducts.
The Mechanics of an Erection.
An erection begins with the nervous system. Messages from the brain travel to nerves within the penis and cause the penile muscles to relax. This relaxation allows blood to flow into the chambers of the corpora cavernosa. The pressure from the blood causes the chambers to expand, increasing the size and firmness of the penis. When the muscles contract, the blood flows out of the chambers, signaling the end of the erection.
Many factors are at work here: the nervous system, blood flow, and the action of muscles. Problems at any point in the process can shorten the duration of an erection or even prevent one from occurring