Editing Appendix (anatomy) (section)

===Maintaining gut flora===
[[File:Appendix function diagram.svg|left|thumb|A possible function of the human appendix is a "safe house" for beneficial bacteria in the recovery from [[diarrhea]]]]

Although it has been long accepted that the immune tissue surrounding the appendix and elsewhere in the gut—called [[gut-associated lymphoid tissue]]—carries out several important functions, explanations were lacking for the distinctive shape of the appendix and its apparent lack of specific importance and function as judged by an absence of side effects following [[appendectomy|its removal]].<ref name="PBD4thEd">{{Cite book |author1=Kumar, Vinay |author2=Robbins, Stanley L. |author3=Cotran, Ramzi S. |title=Robbins' pathologic basis of disease |publisher=Saunders |location=Philadelphia |year=1989 |pages=[https://archive.org/details/robbinspathologi00robb/page/902 902–3] |isbn=978-0-7216-2302-3 |edition=4th |url-access=registration |url=https://archive.org/details/robbinspathologi00robb/page/902 }}</ref> Therefore, the notion that the appendix is only [[vestigiality|vestigial]] became widely held.

William Parker, Randy Bollinger, and colleagues at [[Duke University]] proposed in 2007 that the appendix serves as a haven for useful [[bacteria]] when illness flushes the bacteria from the rest of the intestines.<ref name=health>{{cite news |agency=[[Associated Press]] |date=5 October 2007 |title=Scientists may have found appendix's purpose |url=http://www.nbcnews.com/id/21153898/ |url-status=dead |work=[[NBC News]] |archive-url=https://web.archive.org/web/20200204135004/http://www.nbcnews.com/id/21153898 |archive-date=4 February 2020 |access-date=24 August 2019}}</ref><ref name="JTBpaper">{{cite journal | vauthors = Randal Bollinger R, Barbas AS, Bush EL, Lin SS, Parker W | title = Biofilms in the large bowel suggest an apparent function of the human vermiform appendix | journal = Journal of Theoretical Biology | volume = 249 | issue = 4 | pages = 826–31 | date = December 2007 | pmid = 17936308 | doi = 10.1016/j.jtbi.2007.08.032 | bibcode = 2007JThBi.249..826R }}</ref> This proposition is based on an understanding that emerged by the early 2000s of how the immune system supports the growth of beneficial [[gut flora|intestinal bacteria]],<ref>{{cite journal | vauthors = Sonnenburg JL, Angenent LT, Gordon JI | title = Getting a grip on things: how do communities of bacterial symbionts become established in our intestine? | journal = [[Nature Immunology]] | volume = 5 | issue = 6 | pages = 569–73 | date = June 2004 | pmid = 15164016 | doi = 10.1038/ni1079 | s2cid = 25672527 }}</ref><ref>{{cite journal |author1=Everett M.L. |author2=Palestrant D. |author3=Miller S.E. |author4=Bollinger R.R. |author5=Parker W. |title=Immune exclusion and immune inclusion: a new model of host-bacterial interactions in the gut |journal=Clinical and Applied Immunology Reviews |volume=4 |pages=321–32 |year=2004|doi=10.1016/j.cair.2004.03.001|issue=5}}</ref> in combination with many well-known features of the appendix, including its architecture, its location just below the normal one-way flow of food and germs in the large intestine, and its association with copious amounts of immune tissue. 

Research performed at [[Winthrop–University Hospital]] showed that individuals without an appendix were four times as likely to have a recurrence of [[Clostridioides difficile infection|''Clostridioides difficile'' colitis]].<ref>{{cite web |url=https://blogs.scientificamerican.com/guest-blog/2012/01/02/your-appendix-could-save-your-life/ |title=Your Appendix Could Save Your Life |last=Dunn |first=Rob |date=January 2, 2012 |publisher=[[Scientific American]] |access-date=22 December 2016 |url-status=live |archive-url=https://web.archive.org/web/20201111234503/https://blogs.scientificamerican.com/guest-blog/your-appendix-could-save-your-life/ |archive-date=11 November 2020}}</ref> The appendix, therefore, may act as a "safe house" for beneficial bacteria.<ref name="health" /> This reservoir of bacteria could then serve to repopulate the [[gut flora]] in the [[human digestive system|digestive system]] following a bout of [[dysentery]] or [[cholera]] or to boost it following a milder gastrointestinal illness.<ref name="JTBpaper"/>