Strange, Ugly, Amazing: Scrotums

First thing’s first – if you’re reading this, it means you actually clicked through to read something with “scrotum” in the title. On the internet. Pretty ballsy, don’t you think?

(Hey, just because this is a site dedicated to the pursuit of information doesn’t mean anyone signed away the rights to make a few ball jokes.)

Now then, let’s talk scrota. Almost all male mammals have a scrotum, the small sack of skin that houses the testicles.¹ Basically, scrota are just relatively thin layers of skin with a bunch of sweat glands and no subcutaneous fat. Inside, there are two chambers separated by a septum. Outside, they’re hairy and veiny and wrinkly. And generally, we can all agree that it’s an ugly bit of human.

But if you want to talk functionality, the scrotum is a goddamn prince. To ensure the successful manufacture of sperm – spermatogenesis – the testes need to remain just below our normal body temp. Copious sweat glands and lack of fat help the scrotum achieve thermoregulation, as does the ability to dangle. And when it gets chilly, contraction brings the boys back up to the comfort zone.²

Now then. What of the little seam that runs from the root of the penis to the anus?

Vesling’s Line

First, it’s called the Raphe scroti, which is Latin for “seam of the scrotum.” It is also sometimes called Vesling’s Line, after Johann Vesling, a German anatomist and botanist back in the 1600s.* And, if you’re just looking for a fun, new descriptor, you might try to work “longitudinal eminence” into some foreplay.

On to the second question, why the hell is it there?

The scrotum starts to form when a human embryo is around 8 weeks old. So if you’ve never before considered how a human being is conjured out of sperm and egg, this part takes a bit of time-lapse imagination.

Picture this little pink creature less than an inch in size. It’s only just lost its tail and its legs resemble sea turtle flippers. At its base, there are two tiny flaps of skin called the labio-scrotal folds – a name that sort of ruins the ending. In women, the folds eventually elongate into labia majora and form around the “genital eminence,” which will be the clitoris. In men, the folds grow up, out and around until they meet in the middle and fuse, creating a cozy pocket of skin into which the testes will one day descend. The folds continue to seal, from the middle (perineum, taint) all the way up to the tip of the penis (genital eminence) and down the opposite direction toward the anus. Think of it like a Ziploc bag that’s closed except at the corners.

All in all, the Raphe scroti is a souvenir of the wonder that is mammalian genital development. Bear it with pride.

¹Dolphins and elephants are among the scrotum-less.

²For thermostat regulation tighter than your grandma’s house, thank the cremaster muscle. It’s also on guard for fight or flight situations, because vulnerable reproductive organs are the last thing you need when there’s a hyena on your tail.

Bittel Me More

Cunningham’s Textbook of Anatomy

Reproduction in Domesticated Animals