Your appendix is ​​not, in fact, useless. This anatomy professor explains

It was the first day of spring break in Phoenix in 1992, and 12-year-old Heather Smith was excited about her family’s upcoming ski trip.

But before Smith and her family had even packed their snow pants, she realized she wasn’t feeling well. “I woke up feeling a little nauseous, and I wasn’t sure why. As the day went on, I started feeling worse and worse and had stomach pains,” she says.

Around noon, her father took her to the emergency room. She ended up having emergency surgery to have her appendix removed.

Smith still has a small scar from the appendectomy. And after the surgery, she became intrigued by the part of her body she had lost so suddenly. “It inspired me to wonder: Why do we have this weird little organ in the first place? What does it do? Why does it get inflamed?”

Smith grew up to become a professor of anatomy at Midwestern University and editor-in-chief of a magazine called The anatomical record. And all these decades later, Smith has made a mark in the field by studying the organ that ruined her family’s vacation plans in 1992.

She acknowledges that the appendix has a bad reputation as a useless organ that can cause pain and require emergency surgery. “But recent research shows that it does have functions that can help us,” she says.

NPRs Short wave spoke to Smith about what the appendix is ​​good for and how a future could emerge where appendicitis can be prevented or treated without emergency surgery.

This conversation has been edited for length and clarity.

What and where is the attachment?

The type of appendix that humans and some primates and rodents have resembles a small worm. It is about the size of your pinky finger and protrudes from the cecum, the first part of the large intestine.

You can identify the location based on a landmark called McBurney’s point. So if you draw a line between your belly button and the part of your pelvis that sticks out [on the right]two-thirds of the way down, that’s about where the appendix is.

How did scientists come up with the idea that the appendix was useless?

There had been a lot of discussion about what the appendix could do as a function, whether it would serve a function [Charles] Darwin’s time. The [fact] that we can live without it provides some support for the idea that it is vestigial and doesn’t actually do anything. And so Darwin’s interpretation of it as a remnant was reasonable at the time, given the information he had.

But now with modern technology we can see things like the microanatomy and the biofilms in the appendix, and we have a better understanding of what it is and what it does.

How has the appendix evolved over time?

If you map the distribution of the appendices across a phylogeny – a tree of life for mammals – you can interpret that the appendix is ​​actually evolved independently. It has appeared independently several times throughout mammalian evolution. So that is proof that it must fulfill an adaptive function. It is unlikely that the same type of structure would continue to appear if it did not play a useful role.

So what are the beneficial roles of the appendix?

It turns out that the appendix seems to have two related functions. The first function is to support the immune system. The appendix has a high concentration of immune tissue, so it helps the immune system fight off any bad things in the intestines.

The second function it performs is what we call the safe house. So this was a hypothesis put forward by a team of Duke University in 2007. And they argued that the appendix could serve as a safe reservoir for the beneficial gut bacteria we have.

In times of gastrointestinal distress – you know, an episode of diarrhea where all your good gut bacteria is more or less flushed out of the system – the appendix is ​​like a blind tube with a very narrow diameter and a narrow lumen, so the good bacteria is not flushed from the appendix. The idea is that it is safe in this time of gastrointestinal distress and that it can then leave the appendix and recolonize these good bacteria in the rest of the intestines.

So the appendix helps us in two ways, both in the intestines: it helps fight invading pathogens, but also to repopulate the intestines with these beneficial bacteria after gastrointestinal problems.

Why do some people get appendicitis?

Appendicitis occurs mainly in the industrialized countries of the world – areas where the fiber content of the diet is generally lower. So one hypothesis is that with the lower fiber content, we are more likely to ingest small pieces of food that are digested and retained. [inside] the appendix and interrupts the blood supply and causes inflammation.

The other hypothesis that doesn’t seem so plausible today has to do with an old idea called the hygiene hypothesis. The idea is that we’re sanitizing so much these days, with all our antibacterials and all our antibiotics that we take, that our immune systems don’t develop properly because they’re not exposed to the full range of pathogens that we otherwise would have. . And so the immune system overreacts and panics. And because the appendix contains so much immune tissue, this is one of the areas where this manifests.

Could this new insight lead to new treatments?

I think there are some promising treatments out there. People are exploring antibiotics and other ways to treat appendicitis without removing it completely, given the mounting evidence that it is in fact beneficial to your health to have an appendix. Studies have shown that infections involve the really bad, nasty bacteria C. difference are typically higher in people who have had their appendix removed.

So there are health benefits to keeping the appendix. In an ideal world we would have a future where we don’t always have to remove it.

What have you learned from studying this ‘weird little organ’?

I think this study has shown me how important it is to look at small anatomical details. Anatomy is just the study of the body, so you might think it’s a dead science. You would think we know everything about the body, especially the human body.

But it turns out that there is actually much more variation, function, and microanatomical adaptations that have not yet been fully realized. So it’s definitely worth doing just descriptive studies of exotic animals that have never been described, or looking at small parts of our own bodies that haven’t been well documented.