What Do My Testicles Do All Day?

An expert in erectile dysfunction explains what our testes are doing day in and day out—from doubling in size to changing the length of their dangle.


From the outside, every set of testicles is unique, like a shrivelled up snowflake. Some mens’ left teste hangs lower than their right (being unsymmetrical means they take up less space); right testicles are usually larger and hang higher (UrbanDictionary defines left testicle as “the testicle no one likes because it’s the one slacking while the right one does all the work”). There’s no standard scrotal pigmentation, either, even on the same guy, so don’t expect any kind of matching colour scheme down there.

But despite all these cosmetic differences, they all look the same on the inside—like two bunches of congealed spaghetti, if you were wondering. But while we all know that your bean bag looks like a hairy brain already, most of us don’t really know what’s going on in there all day. Do your testes just hang around down there, churning out the goods 24/7? Do they ever get to take a load off—say, after we get to take a load off? We checked in with DSC’s go-to expert in all things testicle, Dr. Muhammad Mirza, to get a vehicle report on exactly what’s happening in our undercarriage.

As you might expect, the primary job for testicles is indeed to crank out sperm—relentlessly. “It’s a continuous process,” Mirza explains. “It never stops, it never pauses.” He adds, however, that while the process never turns off, it does fluctuate, depending on circadian rhythmss (the natural cycles your body passes through during sleep) and a slew of variables—once you ejaculate, for example, production really kicks into high gear.

Start to finish, it takes 72 days to produce a sperm, during which it makes an epic journey through 25 feet of testicular microtubes—the equivalent of a human walking 180 miles. The primary scrotal transportation route, known as the epididymis, is itself a 20ft long, crescent-shaped mass of thin tubes, but they’re coiled so tightly that the entire mass is only around 1.5 inches.

Despite the modest size of the testicles, there is no cap in capacity: The idea that you need to ejaculate regularly to get rid of outdated sperm is, according to Mirza, a myth. Every second, the average man produces 1,500 sperm—200 million every day, over three trillion in a lifetime. Those not released after a period of time are simply absorbed back into the body and new sperm is manufactured in their place. A nocturnal emission (the fancy term for a wet dream) may occur, but they’re not an indication that your danglers are bursting with expired sperm, desperately in need of release.

Your testicles do expand from time to time, though—they can grow up to twice their regular size during sex, since the whole region is flooded with blood during sexual activity. As such, in much the same way the length of the shaft expands during intercourse, the testicular volume increases too, resulting in them becoming bigger and harder. If they don’t get relief—and blood stays trapped in there for some time—you might experience the pain that is affectionately known as blue balls.

Your low-hanging fruit are also changing up the length of their dangle all the time. Sperm require a precise environment—four degrees cooler than body temperature—which is why the scrotum is always hanging at slightly different lengths throughout the day. This happens thanks to the cremaster muscle (no, seriously, that’s the name), which contracts to pull the testicles close to the body when they get too cold, then relaxes to let them hang lower when it gets warm.

Another thing testicles do from time to time, of course, is form tumours. Testicular cancer occurs when cancer cells form in one or both testes and begin to grow uncontrollably. Exactly why this happens is unclear, but the chance that testicular cancer may develop increases with certain risk factors, including geography (the highest rate of testicular cancer occurs in white men in northern Europe); family history (brothers and sons of affected men have an increased risk); undescended testicles (some babies are born with one or both testes which have not come down into the scrotum and are at increased risk of developing cancerous tumors); infertility (infertile men with an abnormal sperm count have a slightly increased risk); Klinefelter’s syndrome; and HIV/AIDS.

Most often, testicular cancer is detected as a painless lump in one of the testicles. When found early, the cure rate is close to 100%, which is why self-exams, beginning at puberty, are so vital. Just don’t squeeze too hard while checking yourself out: This can cause the body to release so much adrenaline that it can actually kill you. “Testicles are hypersensitive organs,” Mirza explains. “It’s a protective mechanism against any kind of trauma. When there is trauma, certain hormones like adrenaline will release so that our bodies are aware that that particular part of the body is getting traumatised.”

Bottom line: there’s a lot going on down there—more than we think. So next time you mindlessly reshuffle the contents of your pants, give ’em a (very light) pat on the back, because they’re working their butts off for you.