[♪ INTRO].

There are a lot of things that we get wrong about our human anatomy, but the hymen may very well be the most misunderstood structure we've got. People think it's this thick barrier at the entrance of the vagina that's intact until it's broken by sex, making it a sign of virginity.

But that... none of that's true. The hymen is actually a thin, elastic, membrane at the edge of the vagina's entrance, and how it looks at any given point in a person's life has very little—if anything—to do with sex. The hymen exists because of how the vagina forms.

During fetal development, it starts as a tube of solid tissue between the outside of the body and the organ that will essentially become the uterus. Over time, the inside of this tube just disintegrates to make the reproductive tract. But it usually doesn't completely hollow out— a thin membrane tends to remain on the outer end of the tube.

And that's the hymen. Within a few days of birth, this membrane usually develops one or more openings in it, the exact size and shape of which can differ. Often, though, the hymen just ends up a rim of tissue that only partially covers the vaginal opening.

Some people are even born without a hymen altogether, which doesn't seem to be a problem because as far as anyone can tell, the hymen has no biological purpose. In fact, having a completely intact or imperforate hymen can be a bit of a problem, because when puberty rolls around, it doesn't let menstrual fluids out. Luckily, it's rare—imperforate hymens are estimated to occur in only 1 in 1,000 to 1 in 10,000 people with vaginas.

Not only do hymens generally have holes in them from infancy, but there's also nothing else about them that can be used to reliably indicate sexual activity. For one thing, the tissue is fairly elastic in adults, so penetration doesn't necessarily cause any lasting changes. For example, in one study from 2004, there was no difference in hymen size between people who'd had intercourse and those who didn't.

In fact, more than half of participants who'd had intercourse showed no visible changes to the tissue that might indicate sexual activity, like notches from healed tears. Meanwhile, some of people who didn't have sex did have those notches—which is probably because the hymens can look different for all sorts of reasons unrelated to intercourse. Vigorous exercise or even inserting a tampon might stretch the tissue or cause small tears, for example.

And contrary to most hymen myths, even if the tissue is torn or ruptured somehow, there often isn't a significant amount of bleeding because the hymen has relatively few blood vessels. So there's basically nothing right about the idea that people will bleed when they first have vaginal intercourse because their hymens are being broken. In fact, several studies have documented that bleeding is not routinely observed after a person's first time.

So while it's an interesting artifact of development, there are lots of reasons why the hymen doesn't tell you anything about a person. Thanks for asking! And a special thank you to our patrons on Patreon, who help us keep making educational videos like this one, that sponsors... might not be as interested in.

If you liked learning the truth about this misunderstood body part, I bet you'll love our episode on enduring myths about human reproduction. And if you learn something new, tell us in the comments! [♪ OUTRO].