Erection: how it works
To understand how the male body produces an erection it will help to first understand a little about blood flow through the penis.
Blood supply to the erectile tissue of the penis
The 2 cigar-shaped corpora cavernosa run the length of the penis and make up the bulk of the spongy erectile tissue of the penis. During an erection, these fill with blood.
The blood flows into the erectile tissue mainly via 2 deep central arteries (also known as the cavernosal arteries) — one runs down the length of each corpus cavernosum.
Blood flows out of the erectile tissue through the drainage system of open veins around the outside wall of the corpus cavernosum.
How an erection is produced
|1. You become sexually stimulated by a thought or action.|
|2. Your body releases a chemical known as nitric oxide, which is known to dilate blood vessels.|
|3. The nitric oxide triggers the action of guanylate cyclase, an enzyme that helps activate an erection. It works by prompting the release of a body chemical called cyclic guanosine monophosphate (cGMP). This causes the smooth muscle cells in the penis’ erectile tissue to relax.|
|4. When the smooth muscle cells relax they allow the central artery and other incoming blood vessels to widen as well as the mesh of spongy erectile tissue. This allows more blood to flow via the central artery into the spongy erectile tissue of the penis.
As the 2 cigar-shaped corpora cavernosa fill with blood, the spongy tissue presses up against the veins in the outside walls of the corpora cavernosa, compressing them and stopping the blood from flowing back out of the penis. With more blood flowing in and less flowing out, the penis becomes erect.
|5. The body produces an enzyme known as phosphodiesterase 5 (PDE5). After a signal, such as orgasm or interruption, PDE5 breaks down the erection-causing body chemical cGMP and blood is redirected back out of the penis and into the rest of the body.|
|6. Your penis returns to its previous limp (flaccid) state.|
Last Reviewed: 01/12/2015
1. Tracey DJ, Baume P. Anatomica: The Complete Reference to the Human Body and How it Works. Random House Australia, 2000. 2. Andrology Australia. How an erection works: the details (17 Aug 2015). https://www.andrologyaustralia.org/2015/08/how-an-erection-works/ (accessed Nov 2015).
Video: Erectile dysfunction
Erectile dysfunction, also known as impotence, is when a man has difficulty having an erection. Most men will experience it at some point in their lives and it can be stressful. If it is ongoing or causing problems, there are multiple treatment options available.
If you have impotence (erectile dysfunction), the treatment your doctor recommends will depend on the severity of your symptoms and the underlying cause of your impotence.
Diabetes and sexual health
Sexual problems as a result of having diabetes can affect both men and women. Find out about the causes and treatments.
Erectile dysfunction: visiting your doctor
Find out what questions a doctor may ask when discussing erectile dysfunction (ED, or impotence). Also, see what tests or investigations may be recommended and how ED is diagnosed.
Priapism, a persistent erection not caused by sexual desire or stimulation, is caused by problems with the nerves or blood vessels in the penis, which results in blood remaining trapped in the penis.