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How Do Erections Work?

Katelyn Hagerty

Medically reviewed by Katelyn Hagerty, FNP

Written by Our Editorial Team

Last updated 8/7/2021

Because erections are easy to come by, the process of getting it up can easily be taken for granted. It can be like breathing.

This is especially true when, without thinking too deeply about it, you get excited in the presence of someone you’re attracted to. 

The same goes for those not-as-fun moments where you stiffen for what appears to be no reason at all, when going about your day.

However, while erections can come as easily as walking or taking a bite of delicious pizza, the changes your body undergoes to switch from soft and flaccid, to roaring-to-go make for a complex and interesting event.

Read on to learn how erections work, including a look at the parts involved to ensure you’re able to achieve one. An erection when you want one can be a key factor in your quality of life. 

The Anatomy of a Penis

Erections are  a familiar part of your sex life and key sign of sexual desire. Here’s more about what helps keep your erection firm enough to engage in satisfying sex.

The following common parts are what make up the magic of erections:

  • The shaft: which contains the urethra, a duct that permits urination. It also encloses three cylindrical chambers: the corpus cavernosa (which is actually two chambers — see below) and corpus spongiosum.

  • The head: aka the tip or glans — which is usually the most sensitive part of the penis. It contains an opening for semen, pre-ejaculate (pre-cum) and urine to pass through. In uncircumcised men, this part is usually enclosed in a foreskin.

  • The corpora cavernosa: which includes a pair of spongy erectile tissues that run along the sides of your penis. This spongy tissue fills with blood during arousal to form erections.

  • Corpus spongiosum: which is made up of erectile tissue that houses the urethra. It also fills with blood to ensure the formation of erections.

A maze of blood vessels, connective tissue and nerves also make up the penis.

So, How Do Erections Work?

From a non-technical standpoint, erections are the direct result of some sexual stimulation that takes you from a relaxed point A, to a strong and excited point B.

However, while things may appear simple on the surface — penile erections aren’t exactly a flip-switch reaction. 

In fact, this process is the result of a fast-paced series of events that require the teamwork of blood vessels, erectile tissues, nerves, gases and other moving parts.

Following a sexually stimulating encounter, the body engages in a release of nitric oxide which helps to relax smooth muscles in the penis. 

This relaxation allows for increased blood flow into the penis, which is necessary to get the ball rolling for erections to take place. 

In cases when an insufficient amount of blood fills the penis, this can affect your expectations, and the satisfaction derived from intercourse. (In other words, you may not get hard.)

To allow for this necessary relaxation, nitric oxide stimulates the production of cyclic guanosine monophosphate (cGMP) — which helps induce the smooth muscles to relax by closing calcium channels within the penis. Low calcium levels force the penile muscles to relax.

The blood sourced from this relaxation of the smooth muscles flows into the corpora cavernosa which you'll remember, are two cylindrical tissues within the penis. 

This process increases blood flow within the penis by almost 20 to 40 times its usual amount. 

When these cylinders are full, their weight compresses veins within the penis, reducing the chances of blood flowing out of it. 

The increased blood pressure encourages the penis to become rigid, forming an erection. 

To prompt the penis later return to a flaccid state, the body produces an enzyme known as phosphodiesterase. This enzyme degrades cGMP, redirecting blood out of the penis to other parts of the body. 

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How Does Ejaculation Occur?

While ejaculations and orgasms occur simultaneously or very shortly apart from each other, these experiences are not one and the same.

Orgasms are a mental and emotional event: Think back to that nice and tingly sensation you felt around the time your last sexual encounter ended. 

In comparison, ejaculation is a physical occurence that requires the ejection of seminal fluid (sperm) from the urethra. 

This process is a reflex action controlled by the central nervous system.

When you reach climax and ejaculate, your body goes through two phases:


Emission occurs when the internal penile muscles contract to bring the ejaculate (sperm) to the urethra.

The very first phase of this process ensures that the bladder neck is closed to prevent seminal fluid (liquid that helps with transporting sperm) from spilling into the bladder. 

The sperm that will eventually be ejaculated is produced by the vas deferens (tubes that store and transport sperm from the testes).


As the very obvious name suggests, ejection refers to the expulsion of sperm from the urethra followed by its exit from the penis.

This process is heavily coordinated by the actions of the bladder neck, urethra and other internal parts.

However, while the familiar sensations that accompany the ejection of sperm take place down below, you should know that this process is dependent on a reflex that originates from your spinal cord.

What Happens When You Can’t Have an Erection?

With a better understanding of the processes that come together to grant you rounds of intimate pleasure, it’s expected that you’ll have a deeper appreciation every time you achieve a penile erection. 

This is especially true when you find that your ability to maintain and keep an erection isn’t always guaranteed.

Erectile dysfunction makes it difficult to get or maintain an erection long enough to engage in satisfying intercourse. 

This condition affects close to 30 million men in the US alone, making it a widespread challenge.

Any number of factors may interfere with normal erectile function. For example, chronic health conditions such as cardiovascular disease or heart-attack causing high blood pressure can lead to ED. 

Likewise, diabetes which is commonly caused by high blood sugar may affect your ability to produce normal erections. 

Other physical causes include kidney issues, multiple sclerosis and Peyronie’s disease.

ED may also be caused by mental health conditions such as depression and anxiety, performance fears or emotional issues that stem from stress or relationship problems.

How to Get Stronger Erections

Despite being so common, there are a number of trusted treatment methods to help manage erection trouble. 

To produce an erection sufficient to please you and your partner, the following treatment methods may be employed:

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The Straight-Up on How Erections Work

Generally speaking, and as gone into detail above, erections happen when you become sexually stimulated (physically or mentally), causing blood to fill the penis.

If you’re not experiencing regular erections or they don’t last long enough to enjoy intercouse, it’s a good idea to reach out to a healthcare provider to learn more about erectile dysfunction and any potential causes you might be experiencing. 

Your provider can also provide treatment options to help you lead a more enjoyable sex life.

6 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

  1. Sam P, LaGrange CA. Anatomy, Abdomen and Pelvis, Penis. In: StatPearls Internet. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved from:
  2. Sooriyamoorthy T, Leslie SW. Erectile Dysfunction. In: StatPearls Internet. Treasure Island (FL): StatPearls Publishing; 2021 Jan. Retrieved from:
  3. Panchatsharam PK, Durland J, Zito PM. Physiology, Erection. In: StatPearls Internet. Treasure Island (FL): StatPearls Publishing; 2021 Jan. Retrieved from:
  4. Shafik, A., & El-Sibai, O. (2000). Mechanism of ejection during ejaculation: identification of a urethrocavernosus reflex. Archives of andrology, 44(1), 77–83. Retrieved from:
  5. Revenig, L., Leung, A., & Hsiao, W. (2014). Ejaculatory physiology and pathophysiology: assessment and treatment in male infertility. Translational andrology and urology, 3(1), 41–49. Retrieved from:

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

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