How an erection works

The mechanism that causes your penis to become, and stay, erect includes several key components. Your erectile dysfunction treatment will depend on which of these components is not working properly for you.

In this video, you’ll learn:

  • A normal erection requires:
    • Strong blood flow into the erectile tissue
    • Healthy veins that compress to hold the blood in the erectile tissue
  • The cause of an erection is arousal, which stimulates the release of nitric oxide from nerve terminals and blood vessels. That increases the amount of blood that flows into the erectile tissue.
  • As the erectile tissue fills with blood, the veins that drain the blood out of the penis collapse. That prevents blood from leaving the erectile tissue and keeps the penis erect.
  • Veno-occlusive disease can affect the health of those veins so that they lose their ability to prevent the blood from leaving the penis. That makes it difficult to maintain an erection, no matter how well the blood flows into the erectile tissue.
Last reviewed: 
August 2020

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