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Ever wonder what that dangling thing in the back of your throat is good for? Hank Green explains in this episode of SciShow Quick Questions.

Hosted by: Hank Green
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Sources:
Etymology of “uvula”
http://www.etymonline.com/index.php?term=uvula

Why do we have a uvula?: literature review and a new theory http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2273.2004.00886.x/abstract

Structure of the human uvula http://www.tandfonline.com/doi/abs/10.1080/00016489950180685

A histological comparison of the uvula between snorers and non-snorers http://onlinelibrary.wiley.com/enhanced/doi/10.1111/j.1365-2273.1995.tb01591.x

Morphology of the uvula in obstructive sleep apnea http://www.ncbi.nlm.nih.gov/pubmed/2782743
Hank Green: That thing dangling from the back of your throat, wiggling about if you out breathe with your mouth wide open, what, what is that?

Assuming you haven't been invaded by little throat monsters, that's just your uvula, meaning small bunch of grapes in Latin, because I guess that's what that looks like?

That little bundle of flesh at the back of our throats helps with four different things that all happen to start with S: swallowing, saliva, speech and snoring, and humans are the only mammals that have them.

Uvula hangs from the soft palate, the fleshy bit behind the roof of your mouth, which mainly stops food from going up your nose when you swallow, so that's good.

It does this by covering up your nasal passage just as your chomped up sandwich passes by. Parts of the soft palate produce a thick, goopy kind of saliva that helps the food go down, but the uvula has its own brand of spit. The inside of the uvula is packed full of glands that can quickly make large amounts of thin, watery saliva. These glands are connected to muscle fibers that run through the uvula. When those muscles contract, for example while you're speaking or swallowing, more saliva is released. 

The shape of the uvula helps it swing back and forth like a wet wrecking ball, spreading the saliva around and keeping the inside of your mouth and throat well lubricated while you're chatting or eating.  

The muscles inside of the uvula are capable of rapid, repetitive movements, just what's needed for complex speech and singing. They are particularly helpful if you are trying to like make this noise...rrrrrr....rrrrrrrrrrr....

The uvula, soft palate and tonsils are also the first lines of defense against bacteria and viruses invading our mouths. If the uvula's immune cells can't fight off the infection, it can get painfully swollen.

Enlarged uvulas are also found in people who snore or suffer from obstructive sleep apnea, where sleep is interrupted by parts of the throat cutting off air flow at night. The repetitive stress of each snore might be what's making the uvula so inflamed.

A swollen uvula is unpleasant. It brushes up against the back of the tongue, usually triggering a gag reflex and making you feel like there's something large stuck in your throat, even when there's nothing there.  On the other hand, some people who don't have much of a gag reflex get uvula piercings.

Ahhhh...

It's also possible to remove the uvula if it's causing problems, and people actually manage just fine with most of it missing. Often their main complaint is a chronically dry mouth and throat because that thin, watery saliva isn't getting made anymore.

So even though the uvula does lots of different things, it doesn't seem to be vital for any of them, and we don't really know why it evolved in the first place, especially given the problems it can cause.

For now the uvula remains one of the many odd quirks of the human body.

Thanks to Patreon patron Rod Margolis for asking this question, and thank you to all of our patrons who keep these answers coming. If you like to submit a question to be answered, just go to http://patreon.com/scishow and don't forget to go to http://youtube.com/scishow and subscribe.