Once you understand the embryology, there are actually a variety of things like the appendix: they're just the ends of things that come together. The uvula is a great example: embryologically, the two sides of the face separate very early as an opening, then develop a lot of complicated anatomy and fuse back together. The uvula is where that fusion completes and the fusion process completes (returns 0) when the microenvironment variables get to a certain state.<p>The vermiform appendix is where the three tiniae coli come together. Unsurprisingly, the other, rectal, end the tiniea coli don't so much end as they spread out into the longitudinal muscular layer of the rectosigmoid.<p>And of course the wall of the vermiform appendix is full of lymphoid tissue. The whole colonic wall is full of lymphoid tissue!<p>Source: I'm a pathologist. I have looked at way too much colon. And uvula, and pretty much every other bit of tissue you can imagine, under gross exam, under a microscope, and in situ (live in ORs and dead in autopsy suites).<p>This idea that the vermiform appendix is some deep evolutionary mystery is sort of a low point of medicine that occasionally pokes its head up. It ranks up there with male pregnancy, and various birth defects that have given rise to stories of monsters, like Cyclops. Fun stories, completely useless. Please don't invest in anything related to any of those. If you have money burning a hole in your biomedical investment pocket, feel free to reach out.
Story begins:<p>>The appendix is not, in fact, useless<p>>It was the first day of spring break in 1992 in Phoenix, and 12-year-old Heather Smith was excited for her family's upcoming ski trip...<p>Immediate skip.
<a href="https://www.sciencedaily.com/releases/2007/10/071008102334.htm" rel="nofollow">https://www.sciencedaily.com/releases/2007/10/071008102334.h...</a><p>Date: October 8, 2007
Source: Duke University Medical Center
Summary: Long denigrated as vestigial or useless, the appendix now appears to have a reason to be - as a "safe house" for the beneficial bacteria living in the human gut. The gut is populated with different microbes that help the digestive system break down the foods we eat. In return, the gut provides nourishment and safety to the bacteria. Parker now believes that the immune system cells found in the appendix are there to protect, rather than harm, the good bacteria.
I remember two or three times in my early life where I felt appendicitis-like symptoms only for them to go away after a few hours. That was until one night when the pains persisted past midnight. My roommate insisted on taking me to the ER. After several hours there I finally got checked in, had a CT scan, and prepped for surgery. The docs said I did indeed have appendicitis, and in fact had scarring from past episodes. Before the surgery the pain actually started to subside. I wonder if I could have moved past that episode, and if it would have hit me years later.
Even when I was a kid they were starting to understand this. I'm old enough to remember people believing it was useless, maybe even I was told it from a figure of authority at some point, but definitely as a child my memory was "people used to think it was useless, but now we know it isn't ".<p>It's kind if interesting to me that I continually see stories titled like the article over the years. It goes to show that undoing incorrect common knowledge is a long process that isn't really ever completed, because an editor somewhere decided that a title like this would grab people's attention, but to someone like me, this is like a headline that reads "brushing your teeth confirmed to be effective treatment in fighting tooth decay".<p>I've noticed a surge in articles letting me know that the appendix isn't useless, so I assume we figured out a bit better what it actually does, but to me the most interesting part is about knowledge dissemination.
> It turns out that the appendix appears to have two related functions. The first function is supporting the immune system. The appendix has a high concentration of immune tissue, so it's acting to help the immune system fight any bad things in the gut.<p>> The second function that it serves is what we refer to as the safe house. So this was a hypothesis that was put forward by a team from Duke University in 2007. And they argued that the appendix may serve as a safe reservoir for the beneficial gut bacteria that we have.<p>I have to question if the first function is valid. How can the appendix "help fight bad things in the gut" when it's basically a minor piece hanging off the large intestine. It's not like a lot of stuff passes through it or that it really secretes anything (AFAIK). In fact, wouldn't it make a little more sense that the high amount of immune tissue is there because of appendicitis? After all, people that don't die from sepsis tend to have more options to procreate and a less infect-able appendix would tend to make people live longer.<p>The second thing is pretty interesting though. Sort of makes sense. Though I'd imagine that more often than not the "bad bacteria" is going to infest the safe haven and kill the good gut bacteria. I can't see how that wouldn't often happen.
What purpose is served by the little toe?<p>I suspect it provides some (<i>very</i>) marginal help with balancing, at the cost of a microlimb that is particularly exposed to breakage by stubbing. Having broken each of my little toes by stubbing (on different occasions), I can attest that a broken little toe definitely makes it harder to balance. Hell, it makes it hard to stand.<p>I seriously doubt that there's enough strength in a little toe to provide much help with balancing. So given its propensity for injury, why have little toes not evolved away in large bipeds? (I don't think birds or quadripeds are prone to toe-stubbing)
I wonder whether exploratory surgery to try to "squeeze clear" any blockage might be a good idea, though it could easily be a terrible idea, no doubt.
My theory:<p>Appendix acts like a fuse in an electric circuit.<p>As we get appendix infected, gotta iron out the root cause, it's a doorway to finding the lifestyle problem. Instead getting it removed (unless rarely necessary) means, certain first line of defence is taken away.