This information has been reprinted courtesy of the Erectile Dysfunction Information Center (www.erectile-dysfunction-treatment.org) for personal use only.

Anatomy of the penis

The penis is a complex organ. It is made of tissue, muscle, arteries, veins, and nerves. It begins inside your body near your prostate gland.

Your penis serves many important purposes and has a variety of parts.

For an erection, the most important part is the corpora cavernosa. These are two cavities that run the length of your penis and actually fill with blood to create an erection. Basically, the penis is a "hydraulic" machine.

How you get an erection

An erection starts when you become sexually stimulated.

Your nervous system sends chemical messages to your pelvic area. The smooth muscles inside your penis relax. The arteries widen. The corpora cavernosa, acting like a sponge, fill with blood. In fact, the corpora absorb up to eight times more blood than when your penis is flaccid.

As your penis swells and lengthens, the filled corpora cavernosa press against the veins. The pressure greatly reduces the blood flow from your penis. This keeps your erection firm enough for intercourse.

When everything works the way it should, you will keep your erection for as long as you are sexually aroused.

When you cannot get an erection

To get a firm erection, you need a healthy brain, pliable blood vessels, fully functional nerves, and certain hormones.

If you cannot get or maintain an erection, it is because something is interfering with the nerve messages or the blood flow to your penis. Doctors call this erectile dysfunction (ED), or impotence.

Erectile dysfunction can have a psychological cause, but most often the cause is physical.

Some physical causes of ED are:

• Pelvic trauma, which results from accidental injury or prostate treatment.

• Pelvic surgery for conditions of the prostate, bladder, colon, or rectal area.

• Diabetes can damage the nerves or blood vessels that control blood flow to your penis. If you are diabetic, you are up to five times more likely to have erectile dysfunction.

• Vascular problems, including heart disease and hardening of the arteries, can slow or prevent blood flow into the penis. Sometimes veins in the penis may leak, preventing it from staying hard.

• Neurological disorders include spinal cord injury and multiple sclerosis (MS). These, too, can cause erectile dysfunction.

• Medications include prescriptions for high blood pressure, depression and other conditions. Some may cause impotence by interfering with nerve impulses or blood flow to your penis. A change in dose may reduce the risk. NEVER change your medication without your doctor's permission.

• Alcoholism disrupts hormone levels. It can also cause permanent nerve damage and impotence.

• Hormone imbalance caused by certain diseases, such as kidney failure and liver disease, can lead to impotence.

Click physical causes of impotence for more information.

Psychological problems can cause erectile dysfunction. These include stress, worry, and anxiety. However, only about 10% of ED is caused by something in the mind.

Any kind of stress or anxiety can cause temporary erectile dysfunction. Such ED is common and most men experience it at least once during their lives.

Erectile dysfunction is highly treatable

Now that you understand the anatomy of the penis and causes of erectile dysfunction, you should also know that doctors can successfully treat almost all impotence.

There are a wide variety of treatments for erectile dysfunction. They include drugs such as Viagra, penile implants, vacuum pumps, injection therapy, urethral suppositories, vascular surgery, and counseling. Each treatment has advantages and disadvantages. (Click impotence treatments for more details.)

If you need and want treatment, it is likely that you will find one that works for you.

Viagra, which stimulates blood flow to the penis, is a highly successful treatment for many men with impotence. Unfortunately, the drug fails for 30-40% of the men who try it.

When Viagra or other treatments fail, the solution often is a penile implant. Nearly 300,000 men in the U.S. have undergone an implant over the past 25 years. Penile implants are reliable. Long term follow-up studies report a very high degree of satisfaction.

If you think you have ED, find a urologist who specializes in impotence as soon as possible. Once you are diagnosed, work with your urologist and your partner to determine the best treatment for you.

This page revised March 2005

Copyright 2005 Erectile Dysfunction Information Center. All rights reserved. This site contains information about erectile dysfunction (impotence) for men with ED and their partners. Nothing in this site may be reproduced without written authorization from the Erectile Dysfunction Information Center.