Is the Penis a Muscle?

The penis is unlike most other parts of the human body, as it can take different shapes and forms within a few minutes. What can seem like something soft and malleable can quickly turn stiff and firm in a span of seconds.

The primary region where muscles work to control the penis is your pelvic floor, a group of supporting muscles that run from your pubic bone at the front to your tailbone.

But what exactly is it made of? How does it work? Is the penis a muscle or something else?

Is the penis a muscle or an organ?

The penis is composed of several parts, including three columns of spongy tissue: Two are called corpora cavernosa, and the third is the corpus spongiosum. The corpora cavernosa occupy the top of the shaft and fill with blood to cause erections. This blood flow happens when specific nerves are stimulated.

The corpus spongiosum is found on the bottom of the shaft and protects the urethra, the tube through which urine and semen flow.

The muscles involved in erections and moving the penis are the bulbospongiosus, ischiocavernosus and transverse perineal muscles.

"These muscles play an important role in maintaining and sustaining an erection, supporting and stabilizing the penis during an erect state, and aiding with ejaculatory reflexes during ejaculation," said Susie Gronski, D.P.T., a physical therapist and certified pelvic rehabilitation practitioner in Asheville, North Carolina, and a medical advisor at Aeroflow Urology.

How does an erection work?

The parasympathetic system is the part of your central nervous system (CNS) responsible for relaxation. Inside the spongy tissue of the corpora cavernosa, there are smooth muscle cells that, once relaxed and signaled by the CNS by arousal, allow blood to flow in and cause an erection.

"The effect of parasympathetic stimulation to this cavernous muscle results in increased blood flow and engorgement of erectile tissue within the penis," explained Russel Williams, M.D., a board-certified urologist and urological surgeon based in Houston.

The bulbospongiosus and ischiocavernosus muscles compress the veins of the penis during the full erection phase to prevent venous backflow and potential loss of rigidity.

This compression happens with help from the tunica albuginea—a tissue envelope that surrounds the corpora cavernosa and spongiosum—which provides a firm structure for compression and blocking blood flow.

Once the penis is erect, the inflow of blood slows down just enough to maintain stiffness and remains this way until the CNS switches to the sympathetic system, which can happen with ejaculation.

How does ejaculating work?

"Ejaculation is controlled by sympathetic nerve stimulus to the penis and affects pelvic floor musculature, specifically, bulbocavernosus and ischiocavernosus muscles," Williams said.

Contractions of these muscles cause the release of seminal fluid from the prostate and other glands and the seminal vesicles.

The primary region where muscles work to control the penis is your pelvic floor, a group of supporting muscles that run from your pubic bone at the front to your tailbone, and act almost as a hammock for your bladder and bowels. They're also what you use when you try to stop the flow of urine midstream.

The same muscles mentioned previously—the bulbospongiosus, ischiocavernosus and transverse perineal muscles—all rhythmically and involuntarily contract and relax to expel semen from the urethra.

"The bulbospongiosus muscle, in particular, helps eliminate urine from the urethra after emptying the bladder—also known as milking the urethra—and is one of many muscles involved with continence control mechanisms in men," Gronski noted.

What you should know about your pelvic muscles

"The thing to remember is that pelvic muscles are never really 'off' or completely relaxed," Gronski explained.

The key functions of your pelvic muscles are to stabilize, support, and adapt to pressure and load demands placed on the body. The group is vital in bladder and bowel continence control during exertional and non-exertional tasks, bladder and bowel emptying and sexual function.

As is true for the rest of your muscles, general fitness and staying physically active are great ways to support the health of the pelvic floor muscles, Gronski said. Additionally, you can employ Kegel exercises, which are purposeful and intentional pelvic muscle contractions.

To find your pelvic floor muscles, try to stop your urine midstream by clenching the muscles around your urethra and anus as if you're trying not to pass gas. Next, contract these muscles and hold for three to five seconds before relaxing for five seconds. Repeat the contraction and relaxation 10 times, three to four times daily.

"While not everyone should do Kegels, some people can benefit, including those who experience post-void dribbling, urinary incontinence, bladder urgency, ejaculatory control difficulties and erectile difficulties. Remember not to clench your pelvic floor muscles all the time, because it's essential to relax them, too," Gronski said.

"If someone is experiencing weak ejaculation or delayed ejaculation, Kegels focusing on muscles surrounding the penis could help with force production and sensory signaling related to genital arousal, muscle control and orgasm," she added.

However, trying to tense the muscles to keep an erection isn't a good idea.

"I have noticed that men tend to fatigue the pelvic muscles for fear of losing an erection by working hard—no pun intended—to maintain their erection by excessively tensing pelvic muscles throughout the entire sexual encounter," Gronski said, adding that this practice can get in the way of enjoyable sex and does not work.

Instead, focus on Kegels when you're not having sex, keeping in mind the importance of learning to balance contraction and relaxation to learn muscle coordination and control.