The area between the anus and the scrotum is called the perineum. It’s a small patch of skin, roughly 3 to 5 centimeters long in most men, that sits at the very bottom of the pelvic cavity. Despite its size, the perineum plays an important role in pelvic support, sexual function, and urinary control.
Where the Perineum Is and What It Looks Like
The perineum stretches from the pubic symphysis (the joint at the front of your pelvis) to the tailbone, but the portion you can see and feel externally is the strip of skin running from the back of the scrotum to the edge of the anus. Internally, it sits below the main muscle of the pelvic floor and spans between the pelvic bones on either side.
If you look closely, you’ll notice a faint line running down the center of the perineum. This is called the perineal raphe, and it forms during embryonic development when two folds of tissue fuse together. The same line continues along the underside of the scrotum and penis. It has no function in adults, but it’s a visible reminder of how the body assembled itself in the womb.
Muscles Beneath the Surface
The perineum isn’t just skin. Several layers of muscle sit underneath, organized into a shallow and a deep layer separated by a tough sheet of connective tissue called the perineal membrane. The shallow layer includes the bulbospongiosus, which helps with urination and ejaculation, and the ischiocavernosus, which supports erections by maintaining blood pressure in the shaft of the penis. The superficial transverse perineal muscle runs side to side and helps stabilize the central point where multiple muscles converge.
Deeper in, you’ll find another transverse muscle and the urethral sphincter, which gives you voluntary control over the flow of urine. All of these muscles anchor into a dense knot of tissue at the center of the perineum called the perineal body. Think of it as a structural hub: it holds the surrounding muscles in place and keeps the pelvic organs supported from below.
Nerve Supply and Sensation
The perineum is highly sensitive, and that’s largely thanks to the pudendal nerve. This nerve travels through a narrow tunnel in the pelvis called the Alcock canal, alongside a paired artery and vein that supply blood to the area. A branch called the perineal nerve delivers touch, temperature, pain, and pleasure signals from the perineum and scrotum back to the brain.
Because so much nerve and vascular tissue passes through this small space, the perineum is vulnerable to compression injuries. Prolonged pressure from a narrow bicycle seat, for example, can temporarily reduce blood flow or compress the pudendal nerve, causing numbness or tingling.
Why Perineal Length Matters
Researchers measure what’s called anogenital distance (AGD), the span from the back of the scrotum to the edge of the anus, as a marker that correlates with reproductive health. A Stanford-affiliated study found that fertile men had a mean AGD of about 44.6 mm, while infertile men averaged 31.8 mm. A shorter distance has been linked to lower sperm counts and reduced testosterone exposure during fetal development. This isn’t something you can change, but it’s one of the reasons a doctor might measure this area during a fertility workup.
Conditions That Affect the Perineum
Several health issues can involve this area, ranging from minor discomfort to serious emergencies.
- Perineal injury: Blunt trauma from falls, sports, or cycling can damage the blood vessels and urethra running through the perineum. If blood vessels are damaged, erectile dysfunction can develop. In rare cases, a blunt impact can burst a vessel inside the penis, causing a persistent partial erection called high-flow priapism that may last days or weeks without treatment.
- Urinary problems: Damage to the perineum can narrow the urethra or weaken sphincter control, leading to difficulty urinating or urinary incontinence.
- Fournier’s gangrene: This is a rare but life-threatening infection that causes tissue death in the genital region, including the perineum and scrotum. It can develop as a complication of urinary tract conditions, surgery, or trauma and requires emergency treatment.
- Pudendal neuralgia: Chronic compression or irritation of the pudendal nerve causes burning, stabbing, or aching pain in the perineum that typically worsens with sitting.
The Perineum as a Surgical Access Point
Surgeons sometimes use the perineum as a route to reach the prostate gland, which sits just above it inside the pelvis. Compared to going through the abdomen, the perineal approach tends to involve significantly less blood loss, shorter hospital stays (roughly 8.5 days versus 15 days), and lower rates of urinary incontinence afterward. Surgical complication rates are also modestly lower. This route isn’t appropriate for every patient, but it illustrates how the perineum’s position makes it a practical gateway to deeper pelvic structures.
Keeping the Perineum Healthy
Because the perineum supports pelvic floor function, the same exercises that strengthen the pelvic floor benefit this area. Kegel exercises, where you repeatedly contract and relax the muscles you’d use to stop the flow of urine, help maintain the tone of the muscles anchored to the perineal body. If you cycle regularly, using a wider saddle with a cutout or noseless design reduces pressure on the perineum and lowers the risk of nerve compression. Keeping the area clean and dry helps prevent skin irritation and reduces infection risk, particularly after exercise or in warm weather.