Monday, August 24, 2009

New "old" news about the appendix

A recent article in ScienceDaily discusses a new article in the Journal of Evolutionary Biology regarding the evolution of the human appendix.

As you know, Darwin thought that the vermiform appendix was a vestigial, nonfunctional structure "left over" from our evolutionary past.

And if you been using my A&P textbooks for the last ten years or so, you also know that biologists have long suspected (and recently confirmed) that the appendix is no such thing. Its function is to incubate intestinal flora (gut bacteria)—which helps keep the ecosystem of the gut in a healthy balance by repopulating the colon with beneficial bacteria after an illness or other disturbance.

The new journal article, written by some of the same researchers involved in the most recent confirmation of the "incubator model of the appendix," tackles the evolutionary aspects of the appendix.

Want to know more?

Evolution Of The Human Appendix: A Biological 'Remnant' No More.
Duke University Medical Center
ScienceDaily Duke University Medical Center. 21 August 2009.
[Summary of the journal article and its context]
Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix
Smith, et al.Journal of Evolutionary Biology. published online 12 August 2009
[Abstract of the journal article, published in advance of the print version]

Click here for a FREE surgical photo of a human vermiform appendix.


Alex said...

Just because the appendix has a function (bacteria reservoir for one)doesn't mean that it is not a vestigial organ. The fact that it is no longer used for its primary function is what makes it vestigial. Right?

Kevin Patton said...

Interesting point, Alex. I guess it depends on which definition of "vestigial" one uses . . . Darwin's or a more modern definition. And I'd ask what "primary function" means. Wouldn't ANY organs have shifted functions over many generations . . . making ALl organs vestigial. Either way, the point that organs change is the same no matter what we call them.

J said...

Ok, so why do we all know so many people that have had the appendix removed? Why is it such a "faulty" organ? And have we discovered any negative long term problems in those that have had it removed? Are those people more prone to "bad bacteria" overgrowth?

Kevin Patton said...

Joan, those are great questions. I think that appendicitis is so frequent for much the same reason that sinus infection is so frequent: the location, structure, and function of both lends itself to easy infection. In the case of the appendix, it's as if a nursery for ornamental flowers has shifted to growing weeds.

We know that infection of the appendix can easily and quickly progress to peritonitis or other life-threatening conditions. Because people can and do die from complications of untreated appendicitis, then perhaps removal is a good option, eh?

Do some folks suffer from post-appendectomy gut problems. I suggest that they do. Not all, however, just some. For example, the folks on the forum at have shared their experiences with this.

If we happen to get diarrhea, and need the restorative functions of the appendix, we'll have to rely on other methods of recovery. It might not work as well, but hopefully it will work. Making the appendix useful, but not vital, to our survival.

I tell my students that it's like removing a spare tire that is about to explode. I'd rather drive with a spare tire, but if it's going to kill me then I'll ditch it and drive on. Later, if I need that spare, I can always call the auto club to bail me out and hopefully that will work OK. If not, well, at least I'll have survived longer than if the spare tire had blown up on me, eh?

Does anybody out there know of any research data on post-appendectomy gut problems?

J said...

Well now I want to find out why the darn thing becomes inflammed in the first place ..... And post-appy flora problems.......

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