In Praise of the Appendix

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A stylized drawing of a person with appendicitis, showing some of the digestive organs and lightning strikes to indicate pain in the appendix area. Drawing background is purple.

Debbie says:

Here at Body Impolitic, we write more about other aspects of the body than about the actual workings of organs and biological systems, and today is an exception.

This article caught my eye, even though I’ve never had appendicitis, so I still have an appendix. I’ve always been curious I about this “vestigial” organ, which I was brought up to believe does nothing, and yet can cause so much trouble. So I was really pleased to learn that medical science has caught up with (or is beginning to catch up with) the role of the appendix.

Selena Simmons-Duffin, writing for the NPR series “Shots,” offers “Your appendix is not, in fact, useless. This anatomy professor explains.” The article profiles Dr. Heather Smith, who had an emergency appendectomy at age 12 and is now teaching anatomy at Midwestern University and edits The Anatomical Record.

After explaining some of the basics, Smith makes a fascinating evolutionary point:

If you map the distribution of appendices across a phylogeny — a tree of mammal life — you can interpret that the appendix has actually evolved independently. It has appeared independently multiple times throughout mammalian evolution. So that is evidence that it must serve some adaptive function. It’s unlikely that the same type of structure would keep appearing if it wasn’t serving some beneficial role.

Makes sense, so what role would that be? Two roles, apparently. First, the appendix has a high level of immune tissue, so it likely serves an auto-immune function in the gut. The article doesn’t say, but I would be fascinated to know if people who have had appendectomies are likely to have changes in gut health and gut immunity.

The other role is more interesting. Smith says the appendix serves as a “safe house.”

During times of gastrointestinal distress — you know, a diarrhea episode where all of your good gut bacteria is getting kind of flushed out of the system — the appendix is kind of this blind tube with a very narrow diameter and narrow lumen, so the good bacteria doesn’t get flushed out of the appendix. The idea is it’s safe during this time of gastrointestinal distress and it can then exit the appendix and recolonize this good bacteria throughout the rest of the gut.

I think the second one is really cool, and it also reminds me of the non-medical uses of the word “appendix,” which in a book stores material you might need to refer to or call on; a nice resonance.

I’m also pleased with the article’s conclusion:

Anatomy is just the study of the body, so you’d think that it’s a dead science. You’d think we know everything about the body, especially the human body.

But it turns out that there’s actually a lot more variation and function and microanatomical adaptations that haven’t been fully realized. So 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 are absolutely worthwhile.

Cheers for a newly perceived role for a misunderstood organ, and for the value of studying small, off-trail, and dismissed areas of your own field, whatever that may be.

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