How Erections Work

The first step is a hard one. The curious biochemistry behind pitching a tent. Learn the abc’s of how erections work and common causes of erectile dysfunction.

Erections are a fact of life: young boys spend a lot of time trying to make them go away, while older men spend a lot of money trying to get them to come back. Sometimes, the first step is a hard one. Erectile dysfunction (ED) effects 1 in 5 men. So… let’s dig into the woodshed and discuss the nuts and bolts of pitching a tent.

You can think of the penis like a tire. A tire can inflate by pumping it up with air or deflate by letting the air out. Erections work the same way but with blood instead of air. How the blood gets there and is regulated is a pretty impressive biological process.

The penis contains two cylindrical chambers (called corpora cavernosa) that run down the length of the shaft and are composed of spongy tissue capable of filling with blood. The penis also contains an outer sheath (called a tunica) that surrounds the two chambers. The tunica tightens as blood flows into the penis, making the organ more rigid.

The erection: step-by-step

1. The man receives some sort of sexual stimulation. This can be by touch, sight, smell, thoughts, you know… things that get you going. These stimulations cause the paraventricular nucleus in the brain to start sending signals down the spinal cord to nerves in the penis.

2. The nerves release a chemical called Nitric Oxide, which causes the muscle fibers in the corpora cavernosa to relax, and in turn causes blood to flow in and beginning filling the spongy tissue. The signals also tell muscle fibers in arteries that supply blood to the penis to relax, which leads to a large rush of blood to the organ.

3. As the corpora cavernosa chambers inflate, the tunica sheath around the penis begins to tighten which cuts of the veins that transport blood out of the penis. Now the blood is trapped in the chambers causing an increase in pressure and thus the penis becomes erect. In fact, the blood pressure in your penis during an erection can be more than twice as high as the blood pressure in the rest of your body. The result is….

4. Upon orgasm, there is a spike in production of noradrenaline in the penis which causes the muscle fibers in the corpora cavernosa and arteries to contract and reduce the blood flow into the penis. This in turn causes the tunica to relax and blood begins flowing out of the penis and the organ becomes soft again.

What can go wrong?

At some point in life, around 20% of men will experience some form of erectile dysfunction. Approximately 18 million men in the US right now are having some sort of problem getting or maintaining an erection. If you are among them, know that you are not alone. As we have just discussed erections are the result of a complicated biological process that involves the mind and the body and there are a number of things that can cause a malfunction.

As can be expected, the chances erectile dysfunction increases with age. As the body ages, the cardiovascular system declines and blood circulation is poorer. Often times erectile dysfunction, particularly in older men is linked with heart disease or diabetes. In young healthy men, erectile dsyfunction is still relatively common though more often the cause is mental rather than an issue of blood flow. Stress, exhaustion, performance anxiety and the like can create a cycle that makes it difficult for a man to get or sustain an erection. Read more…

Peyronie’s Disease

Peyronie’s disease is a fairly common disorder where the tunica sheath that tightens around the veins of the penis is chronically inflamed. This inflammation can cause the penis to curve abnormally. It can also create divots or indentations, make sex painful or lead to erectile dysfunction. It is easily diagnosed by a general practice doctor, but more commonly treated by urologists.


Priapism is the opposite of erectile dsyfunction. Instead of having a hard time getting an erection, men with priapism have a hard time getting rid of it. These long lasting erections go on longer than 4 hours and are often painful. They are a medical emergency as they can lead to long term damage of the penis and cause future erectile dsyfunction.

References and recommended reading:

  1. “How Erections Work”. Weill Cornell Medical College.
  2. Delvin, D. “Erectile Dysfunction (impotence)”
  3. Krane, RJ et al. “Impotence”. N Engl J Med 1989; 321:1648-1659

Sara SDx

Sara SDx

Editor of Don't Cook your Balls, Co-Founder of, Health Coach and Men's Health Advocate. Passionate about sperm, men's health and helping people build their families.
Sara SDx

Author: Sara SDx

Editor of Don't Cook your Balls, Co-Founder of, Health Coach and Men's Health Advocate. Passionate about sperm, men's health and helping people build their families.

4 thoughts on “How Erections Work”

  1. Keeping the penis clean and healthy is the best way to avoid a host of complications down there. You guys should check out a penis health creme called Man1 Man Oil. It contains several antibacterial and moisturizing ingredients that will keep the area in excellent shape. Easy to use and safe too.

  2. Is it normal that I wake up every morning with an intense erection. I need to masturbate and ejaculate every morning.

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