The human vermiform (“worm-like”) appendix is a 5-10cm long and 0.5-1cm wide pouch that extends from the cecum of the large bowel. The architecture of the human appendix is unique among mammals, and few mammals other than humans have an appendix at all. The function of the human appendix has long been a matter of debate, with the structure often considered to be a vestige of evolutionary development despite evidence to the contrary based on comparative primate anatomy. The appendix is thought to have some immune function based on its association with substantial lymphatic tissue, although the specific nature of that putative function is unknown. Based (a) on a recently acquired understanding of immune-mediated biofilm formation by commensal bacteria in the mammalian gut, (b) on biofilm distribution in the large bowel, (c) the association of lymphoid tissue with the appendix, (d) the potential for biofilms to protect and support colonization by commensal bacteria, and (e) on the architecture of the human bowel, we propose that the human appendix is well suited as a “safe house” for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal tract are purged following exposure to a pathogen.
Randal Bollinger R, Barbas AS, Bush EL, Lin SS, Parker W. Biofilms in the large bowel suggest an apparent function of the human vermiform appendix. J Theor Biol. 2007 Dec 21;249(4):826-31. Epub 2007 Sep 7. View Abstract
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When this hypothesis was published, we (Metametrix) were quite excited to find it. It makes so much sense. Whenever we deem a physical structure “vestigial” or “junk,” it’s suspicious.
I recently blogged on both sIgA and commensal biofilms, and find the topic very interesting. sIgA insufficiency is the most common genetic immunoglobulinopathy, increasing susceptibility to mucosal-related pathology, including Celiac.
The I stands for Interesting
We also know of course, that the microbiota also supports normal function of many extra-intestinal activities. It seems clear that supporting a robust sIgA and predominant microbiota is a first-line intervention for healthy living. And interestingly, if you think about it, our first-morning steps of having breakfast, going to the bathroom and brushing our teeth are all geared toward GI nourishment.