The prostate is not a muscle, but it contains a significant amount of smooth muscle tissue. It’s classified as a gland, roughly the size of a walnut in healthy adults (about 25 grams), and its primary job is producing fluid that becomes part of semen. What makes the prostate unusual is that muscle fibers are woven throughout its structure, giving it the ability to contract and squeeze out its secretions at exactly the right moment.
What the Prostate Is Actually Made Of
The prostate is a mix of two main components: glandular tissue that produces fluid, and a supportive framework called the fibromuscular stroma. That stroma is made up of smooth muscle cells, connective tissue fibers, blood vessels, nerves, and immune cells. In studies of prostate tissue composition, this fibromuscular stroma accounts for roughly half the organ’s volume, with glandular tissue and the spaces within glands making up the rest.
So while the prostate isn’t a muscle in the way your bicep is, calling it “just a gland” undersells it. It’s more accurate to think of it as a gland wrapped in and threaded through with muscle fibers that give it the contractile force it needs to function.
How the Prostate’s Muscle Tissue Works
The smooth muscle in the prostate operates involuntarily. You can’t flex it the way you flex your arm. Skeletal muscles, the ones attached to your bones, are under your conscious control and have a striped appearance under a microscope. Smooth muscle fibers, by contrast, are spindle-shaped, line the walls of hollow organs throughout the body, and are controlled by the autonomic nervous system.
In the prostate’s case, the sympathetic nervous system triggers contraction. Nerve signals travel from a network called the hypogastric plexus and activate receptors on the smooth muscle cells. During ejaculation, this contraction squeezes prostatic fluid out of the glandular tissue and into the urethra, where it mixes with sperm and fluid from the seminal vesicles to form semen. Without that muscular squeeze, the prostate’s secretions would have no way to reach the urethra at the right time.
The Prostate vs. the Pelvic Floor
One reason people wonder whether the prostate is a muscle may be confusion with the pelvic floor muscles that surround it. The levator ani, a group of voluntary skeletal muscles forming a sling across the base of the pelvis, sits right next to the prostate. One portion of this muscle group wraps around the urethra near the prostate like a hammock. When you voluntarily contract it (as in a Kegel exercise), it pulls the urethra and prostate forward and upward, helping close off urine flow.
These are true voluntary muscles, and they’re separate structures from the prostate itself. The prostate sits within this muscular cradle but is not part of it. The distinction matters practically: pelvic floor exercises strengthen those surrounding skeletal muscles, not the smooth muscle inside the prostate.
Why Prostate Muscle Tissue Matters in BPH
The muscular component of the prostate becomes clinically important when the gland enlarges, a condition called benign prostatic hyperplasia (BPH). An enlarged prostate can grow well over three times its normal size, exceeding 80 grams. Urinary symptoms from BPH arise through two distinct mechanisms.
The first is straightforward physical compression: the enlarged tissue presses on the urethra, narrowing the channel urine flows through. The second mechanism is where smooth muscle plays a direct role. The prostate and bladder outlet are densely packed with a type of nerve receptor that, when activated, increases smooth muscle tone. In BPH, this heightened muscle tension adds a dynamic squeeze on top of the physical bulk, further obstructing urine flow. This is why some BPH medications work by blocking those specific receptors, relaxing the smooth muscle and easing the constriction without shrinking the gland itself.
Understanding that the prostate has both a tissue-bulk problem and a muscle-tone problem in BPH explains why treatment often targets one or both of these components. Medications that relax smooth muscle can improve urinary flow within days, while treatments aimed at reducing gland size take longer to show results.
The Short Answer
The prostate is a gland with a muscular component, not a muscle with glandular features. Its smooth muscle tissue is essential for ejaculation and is controlled entirely by your nervous system without any conscious input. That same muscle tissue contributes to urinary problems when the prostate enlarges. The voluntary muscles you can strengthen through exercise are the pelvic floor muscles surrounding the prostate, not the prostate itself.