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  • This episode is sponsored by Squarespace.

  • From websites and online stores to marketing tools and analytics,

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  • [♪ INTRO]

  • The appendix gets a bad rap.

  • You probably never think about it unless it's the reason you're doubled over in abdominal pain.

  • And for the most part, it gets written off as a useless organ left over from our evolutionary past.

  • But even though you can usually ignore it, you've got to give your appendix some credit,

  • because it might not be as useless as you thought.

  • The appendix has evolved in mammals at least twenty-nine times,

  • which is a pretty good sign that it does something.

  • And back in 2016, an international team of researchers set out to understand

  • why it appears so many times.

  • They started by looking at what kinds of things animals with appendixes have in common.

  • But first, they had to define what an appendix even is,

  • since the thing we call an appendix comes in all shapes and sizes across mammals.

  • As a starting point, the researchers defined it as a section of tissue extending from the cecum,

  • the beginning of the large intestine.

  • Then they used computer models to analyze data on hundreds of mammals.

  • They gathered information about their habitats and social behavior

  • and, of course, whether or not they had an appendix.

  • They concluded two things.

  • The first was that the appendix has evolved more times than it's been lost,

  • so it must have some kind of evolutionary advantage.

  • And second, after finding high concentrations of lymph tissue, which protects the body against foreign invaders,

  • they concluded that the appendix is involved in immunity across mammals.

  • And that seems to be the case for humans as well.

  • Within the inner layers of the appendix, we find all kinds of densely packed immune cells,

  • including T and B cells and natural killer cells,

  • which are all important parts of your body's immune response.

  • But we also find a reservoir of good gut bacteria hanging out in there.

  • It's the same type of bacteria that line the insides of the intestine, creating a protective barrier against invaders.

  • Given its prime position just off the colon,

  • researchers think the appendix might dish out emergency rations of gut bacteria in times of crisis,

  • like during cases of extreme diarrhea.

  • Diarrhea can flush out your intestines,

  • but the appendix may be able to provide a fresh population of the gut bacteria

  • that keeps your digestion on track.

  • They say you don't know what you have until it's gone and it's true.

  • One way to appreciate the immune function of the appendix is to see what happens when it comes out.

  • A study published in 2015 found that patients who contracted a particular bacterial infection,

  • called Clostridium difficile, were twice as likely to develop a severe infection

  • if they didn't have an appendix.

  • That study alone doesn't prove that the appendix prevents infection,

  • but it does raise questions about whether or not surgeons should remove the appendix

  • when they don't need to,

  • since that might actually cause trouble rather than prevent it.

  • That said, appendicitis can be deadly, so if your appendix needs to come out,

  • it's coming out.

  • But otherwise, maybe we shouldn't be so quick to dismiss this organ

  • that's usually just trying to be a pal.

  • And speaking of making your life easier, Squarespace makes it painless to design your own website.

  • You don't even have to know how to code!

  • We actually designed the SciShow website in Squarespace

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  • at

  • [♪ OUTRO]

This episode is sponsored by Squarespace.


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B1 中級

あなたの付録は、結局のところ役に立たない (Your Appendix Isn't Useless, After All)

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    林宜悉 に公開 2021 年 01 月 14 日