The Amazing Muscular Origami That Makes The Vagina So Stretchy

The Amazing Muscular Origami That Makes the Vagina So Stretchy

Human vaginas don't have the fantastical loops and blind alleys of a duck vagina, but they still have some pretty amazing shape-changing powers. Here's how they're put together, and how that anatomy lets them grow when they need to.

They certainly need to grow before they're put to use. The average vagina is only about two-and-a-half inches long and a little more than an inch wide when it isn't being used for sex or childbirth. The average erect penis is about twice as long as a resting vagina (and a baby's head nearly four times as wide!), so it's clear that something has to change when the organ's called into action.

An Organ Poised to Shape-Shift

The human vagina is a muscular tube. It opens to the outside world in the vulva and plunges through the muscles of the pelvic floor to meet the cervix.

The Amazing Muscular Origami That Makes the Vagina So Stretchy

Its wall is made up of four distinct tissue types, stacked like a layer cake from the vaginal cavity to the organ's outer edge.

The innermost layer of the vaginal wall is a thick mucous membrane (the white stuff, in the image to the left) that sits atop a network of blood vessels. A layer of smooth muscle fibres underlies the blood vessels, followed by a layer of tough collagen and elastic fibres that mark the outer edge of the vagina.

The wall is folded, forming three-dimensional pleats called rugae that make the inside of the vagina feel bumpy.

Like an accordion, the pleats let the vagina store the extra material it needs to expand -- all the tissue needs is a signal to unfold.

Making Room for Sex

When a women becomes sexually aroused, nerves inside the vaginal wall release two neurotransmitters: nitric oxide (NO) and vasoactive intestinal peptide (VIP). These molecules widen the arteries inside the vaginal wall and let more blood flow into the tissue. They also help relax the smooth muscle in the wall.

The Amazing Muscular Origami That Makes the Vagina So Stretchy

As vaginal tissues engorge with blood their now-relaxed folds extend and make the vagina both longer and wider. Engorgement makes the vagina the right shape to accommodate a penis, and also helps the vagina lubricate itself.

As the tissues fill with blood, plasma leaks from the congested capillary beds, overwhelming the mucous membrane's ability to reabsorb it. It seeps out from between the cells, forming a slick and slippery layer on the inner surface of the vagina that helps keep sex fun.

Making Room for Baby

Fitting over a penis is easy. The vagina has to do some serious remodeling to fit over a baby. The hormones a woman releases during pregnancy preps the tissue in advance.

The Amazing Muscular Origami That Makes the Vagina So Stretchy

Under their influence, the tough collagen supporting the vaginal wall relaxes and smooth muscle fibres disconnect from one another, making the tissue far far stretchier than normal.

During delivery, as the muscles in the uterus contract in concert, the muscles in the vaginal wall relax, and the super-elastic wall expands as the baby squeezes through the birth canal.

You'd think something that drastic would be permanent, but the vagina is back to normal within 6 to 12 weeks. Now that's amazing. [Levin 2002 [Traish et al. 2002 [Munarriz et al. 2003 [Goldstein et al. 2005 [Barnhart et al. 2006 [Farage and Maibach 2006 [Feola et al 2011]] Top image: Theodore Lee via Flickr [CC BY-ND 2.0 ; vaginal wall: Ed Uthman via Flickr [CC BY 2.0; female reproductive organs: Henry Grey (1918) Anatomy of the Human Body via Wikimedia; childbirth diagrams: Frank Netter via Wikimedia]

WATCH MORE: Science & Health News


    Just saying, but what the hell does this have to do with anything resembling technology, gadgets etc? These random, pointless articles are stupid

      Seems like pre-pubescent teenagers are running the roost and have just discovered womens-parts *snigger snigger*.
      I only came here to read the comments, giz. Please stop posting this crap.

        The author is a woman scientist, so you might be off the mark a little. This is part of an ongoing series of biology articles, the rest of which you can see if you click Diane Kelly's name at the top of the page. This article isn't any different to the rest of them. Gizmodo pretty regularly covers science topics, biology is no different to astronomy in that respect.

        That said, there's something amusingly Freudian that while the rest of the articles are mostly quiet, it's an article on the human vagina that attracts 'wah, I don't want to read this' replies.

        Last edited 07/07/15 7:56 am

          Yeah its frigging bizarre. It's pretty clearly a science articles guys. Do you wanna go complain about all the science articles on here? Don't worry, I'll wait, you'll be a while though.

      I would say that a majority of Giz readers are male and probably don't know much about the vagina, so it's a pretty interesting article.

        Really? What is this? The 70s?

        I think you'll find that many of us are or were married and have children that we were there to see born. While I don't have one physically connected to me I've spent enough time around them to know a few things. Still - from a purely biological sense, I do agree this was pretty interesting.

          So you knew that the vagina is made up of four distinct tissue types, stacked like a layer cake from the vaginal cavity to the organ’s outer edge? Because I did not.

            As I said - from a purely biological sense it was interesting, I doubt many women are aware of this fact either and - last time I checked - they actually have one. If I was a proper 70s nerd I would have known that already, of course.

            Pretty much all organs with cavities (like the alimentary canal) are made that way, it's common knowledge, "to those versed in the art", calling it a layer cake is the authors way of sexualizing (making it seem more interesting than it really is) an anatomical norm.

            You just gotta read a bit more, or do a few more college courses.

            Tech, science and weird factoids, are all on gizmodo.

            just taking the piss, don't get riled, honey.

            Last edited 07/07/15 11:29 am

      From another part of gawker called "Throb" that I have no idea why Allure choose to run on Gizmodo. Typically the really out of place American articles aren't pure Gizmodo articles in America.

      Last edited 07/07/15 9:15 am

        You make it sound like a separate website, like the difference between Kotaku and Gizmodo. Throb is a subsection of Gizmodo on the US site.

Join the discussion!

Trending Stories Right Now