Emily Kwon, signed: You’re listening to Short Wave…
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KWON: …From NPR.
Serena Simmons Duffin, host:
Hey there, shortwavers. I’m your host today, Serena Simmons Duffin.
Let’s travel back in time to the early 90’s.
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SIMMONS DUFFIN: It’s spring in Phoenix, Arizona, and 12-year-old Heather Smith is in good spirits. Today is the first day of her spring break, and despite the 80-degree heat every day, her family is on vacation and it’s expected to snow.
Heather Smith: It’s really exciting to go on a ski trip because it’s the Sonoran Desert.
Simmons-Duffin: That’s their plan. But before Heather and her family got ready for their snowpants, she realized…
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SIMMONS DUFFIN: …She doesn’t feel well.
Smith: I woke up in the morning feeling a little nauseous, but I didn’t know why. And throughout the day, I felt worse and worse.
Simmons-Duffin: Her abdomen started to hurt. Her father, a physicist, thought she might have appendicitis.
SMITH: So he took me to the emergency room and sent me to the emergency room. And by about 10 o’clock that same night, I had already had surgery to remove my appendix. I was in the hospital for several days. I still have a small scar on my stomach.
Simmons Duffin: The ski trip never happened. Instead, the family relaxed at their home in Phoenix. And then Heather realized she was obsessed with appendix.
Smith: Why do we have this weird little organ anyway? What is it for? Why does it cause inflammation?
Simmons Duffin: Heather Smith grew up to become a scientist, just like her father. She is a professor of anatomy at Midwestern University. Her campus is near her hometown of Phoenix.
SMITH: So, I’m the editor-in-chief of a journal called The Anatomical Record.
Simmons-Duffin: That’s very official, Autopsy Notes. It’s like being in charge of all aspects of anatomy.
Smith: We publish everything about anatomy. I love it. It’s very diverse. You’ll get all kinds of interesting topics.
Simmons-Duffin: Among all these topics, Heather Smith made a big mark in the field in 1992 by studying a very strange little organ that ruined her family’s ski plans. appendix.
Smith: We often hear about this disease in the context of appendicitis and appendectomy, which is the surgical removal of the appendix. Therefore, we tend not to consider it very useful. However, recent research has found that it has functions that help us.
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SIMMONS DUFFIN: Today on the show, gone are the days when we thought of the appendix as a useless organ that would die unnoticed. We’ll explain what the appendix is good for and how a future may come when appendicitis can be prevented or treated without emergency surgery. You’re listening to NPR’s science podcast SHORT WAVE.
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Simmons-Duffin: OK, Heather, what is the appendix in the human body? Where is it? what does it look like?
SMITH: So the type of appendix that humans and primates and some primates and rodents have is similar to small worms. It’s about the size of your little finger. It protrudes from the caecum, the first part of the large intestine. And you can locate it based on a landmark called McBurney Point. If you draw a line between your belly button, your belly button, and your anterior superior iliac spine, you can feel that bump sticking out, basically at the front of your pelvis. This guy has an appendix on the right side between the two, about two-thirds down.
Simmons-Duffin: I just wanted to note that in one of your papers you show diagrams of different appendages in different species, which is kind of wild. It’s like all these squiggles. It’s like practicing calligraphy or something.
Smith: Yeah. So there are actually several different types of appendices. So humans have this vermiform type, but rabbits, hares, and other lagomorphs have an elongated cecum that seems to taper toward the appendix, rather than another type of protrusion. . And animals like marsupials, monotremes, wombats and echidnas have tiny little projections that just come out of their large intestines, but they don’t actually have a cecum at all.
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SMITH: So it turns out that there are actually a lot of different ways that appendixes can form in the mammalian world.
Simmons-Duffin: Well, for a long time, people thought the appendix was basically like this leftover organ and was useless. And it seems to me that Charles Darwin is one of the people who created this sense that what this is all about is basically nothing.
SMITH: Well, there’s been a lot of debate about what the appendix does as a function and whether it’s been in use since before Darwin’s time. And, you know, the idea that we can live without it lends some support to the idea that it’s a vestige and doesn’t really do anything. But thanks to modern technology, we can now see things like the microanatomy of the appendix and biofilms, and have a better understanding of what it is and what it does. I did.
Simmons-Duffin: So I understand that some of the research you’ve done on the appendix has to do with how it evolved over time and through species. So why such an enlightening quest?
SMITH: So my research team looked at the distribution across mammals, which mammals have an appendix, and what kind of appendix they have, whether it’s an appendix or this elongated caecum. I was interested in speculating how the appendix evolved over time. And what we discovered is that if we map the distribution of the appendix across the phylogenetic tree of mammalian life, we can interpret that the appendix actually evolved independently. Therefore, it has emerged independently many times throughout mammalian evolution. So this is also evidence that it must serve some adaptive function. It is inconceivable that the same type of structure would continue to appear unless it served some useful role.
Simmons-Duffin: So what is their useful role? For example, what were you able to dig out to make the appendix more useful and interesting than you originally thought?
Smith: So we’ve found that the appendix has two related functions. Therefore, the first function is to support the immune system. So it turns out that the appendix has a high concentration of immune tissue that helps the immune system fight off all the bad stuff in the intestines.
The second function it serves is what we call a safe house. This is the hypothesis proposed by Bollinger and his team at Duke University in 2007. And they argued that the appendix may act as a kind of safe reservoir of our beneficial gut bacteria. So when you have gastrointestinal problems, when you have diarrhea where all the good bacteria in your intestines are flushed out of your system, your appendix is like a blind tube with a very narrow diameter and a narrow lumen. Bacteria are not flushed out of the appendix. So the idea is that during this period of gastrointestinal distress, it’s safe and that this good bacteria can come out of the appendix and recolonize the rest of the intestine.
Therefore, the appendix helps us in two ways. It helps fight off invading pathogens, but it also helps repopulate this beneficial bacteria in your intestines after gastrointestinal issues.
Simmons-Duffin: So your gut is like a little pocket of good bacteria.
Smith: That’s right.
Simmons-Duffin: So there’s still some mystery surrounding the appendix. As far as I know, there is no understanding of why some people get appendicitis and others don’t.
SMITH: So appendicitis seems to occur primarily in the sort of developed countries of the world, so it seems like there are a lot of places where the fiber content of the diet is low. One hypothesis is that lower fiber content increases the likelihood of small digestate fragments. That is, things like food that is being digested or small particles of stool that get stuck in the internal cavity. The diameter of the appendix increases, cutting off the blood supply and causing this inflammation.
Another hypothesis, which seems less plausible these days, involves an older idea called the hygiene hypothesis. The idea behind the hygiene hypothesis is that we’ve been disinfecting so much these days that our immune systems aren’t developing properly. The reason is that otherwise the immune system is not exposed to all kinds of pathogens. This causes the immune system to overreact and cause panic. And since there is so much immune tissue in the appendix, he is one of the areas where this appears.
Simmons-Duffin: Well, obviously the appendix has a purpose. And there are a few different ways it could work. But it’s okay to take it out, right? That means people can function without it.
Smith: Yes. That’s one of the reasons. The appendix was long thought to be a remnant, as it has been observed that people can live just fine without it. I haven’t done anything for 30 years and I’m very healthy. However, if you think about other organs, you can live without the spleen. You can live without a nose. But that doesn’t mean it’s useless to have.
SIMMONS DUFFIN: Yeah, sure. Could this new understanding of the role of the appendix lead to a new approach to appendicitis? Because, as you know, today we have laparoscopic surgery. It’s possible – you can come and go. But I’m still in surgery. I still have parts of my body removed. Do you think there is a future in which appendicitis will not occur as frequently, or if it does occur, it may not result in emergency surgery, which is still the treatment option?
Smith: I think there are some promising treatments. People are researching antibiotics and other types of treatments without completely eliminating appendicitis. And with accumulating evidence that actually having an appendix can be beneficial to your health, I think it might happen someday. You know, studies have shown that people who have had their appendix removed tend to have higher rates of infection with his C. diff, which is a really bad bacteria. So in an ideal world, there would be a future where we didn’t have to delete all the time.
Simmons-Duffin: I think the broader question here is, what are you doing? What have you learned from this body of research?
Smith: I think this study shows the importance of looking at anatomical details. So you might think that anatomy is just the study of the body, a kind of dead science. We may think we know everything about the body, especially the human body. However, it turns out that there are many more variations, functions, and microanatomical adaptations that are not fully realized.
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Smith: There’s absolutely value in just doing descriptive research on unusual animals that haven’t been described before, or just looking at small parts of our own bodies that aren’t well documented.
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Simmons Duffin: I feel like we probably need to update our operations. That game – do you know? – Children’s should be updated with all this new information.
Smith: Yes. absolutely.
Simmons-Duffin: It’s like an old globe. You have to maintain your speed.
SMITH: (Laughter).
Simmons Duffin: Heather Smith, thank you so much for teaching me all about appendices and the overlooked benefits of appendices.
Smith: Of course. Thank you for your time.
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Simmons Duffin: This episode was produced by Margaret Cirino and edited by showrunner Rebecca Ramirez. Fact checked by Britt Hanson. Carly Strange was an audio engineer. I’m Selena Simmons Duffin. Thank you for listening to NPR’s SHORT WAVE.
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