View source for Appendix (anatomy)

{{Infobox anatomy
| Name        = Appendix
| Latin       = Appendix vermiformis
| Image       = Grant 1962 172a.png
| Caption     = Drawing of [[colon (anatomy)|colon]] with variability of appendix as seen from front
| Width       = 
| Image2      = Gray536.png
| Caption2    = Arteries of [[cecum]] and appendix (appendix labeled as ''vermiform process'' at lower right)
| Precursor   = [[Midgut]]
| System      = [[Gastrointestinal tract|Digestive system]]
| Artery      = [[Appendicular artery]]
| Vein        = [[Appendicular vein]]
| Nerve       = 
| Lymph       = 
}}
In [[human]] [[anatomy]], the '''appendix''' (or '''vermiform appendix'''; also '''cecal''' [or '''caecal'''] '''appendix'''; '''vermix'''; or '''vermiform process''') is a blind ended [[tube]] connected to the [[cecum]] (or caecum).  

The caecum is a pouch-like part of the [[Colon (anatomy)|colon]]. The appendix is near the junction of the [[small intestine]] and the [[large intestine]]. The term "vermiform" comes from [[Latin]] and means "worm-like in appearance". Its length is approximately 4 to 6 centimetres.

The appendix has no apparent function in [[Human body|the human body]], but it can get inflamed and cause diseases (like [[appendicitis]]). In humans, it is a [[vestigial organ]]. It is assumed the appendix may act as a storage for beneficial ("good") [[Gut flora|gut bacteria]] which aid us on [[Digestion|digesting]] difficult food and fighting germs.

[[Charles Darwin|Darwin]] suggested that the appendix was perhaps used to [[digestion|digest]] leaves as [[primate]]s.<ref name="DescentOfMan">[[Charles Darwin|Darwin, Charles]] 1871. ''[[The Descent of Man]], and selection in relation to sex''. John Murray: London.</ref> Over time, humans have eaten fewer [[vegetable]]s and have [[Evolution|evolved]]. Over thousands of years, this organ has become smaller to make room for the [[stomach]]. It is a [[vestigial organ]] which has degraded to nearly nothing in the course of evolution.

[[Herbivore|Herbivorous]] mammals such as the [[Koala]] have large appendices, and usually other adaptations as well. [[Cellulose]], from [[Plant cell wall|plant cell walls]], is hard to break down. The cecum of the koala is attached to the juncture of the small and large intestines as it is in humans, but is very long. This enables it to host [[bacteria]] specific for [[cellulose]] breakdown.

Early man’s [[ancestor]] may have also relied upon this system and lived on a diet rich in [[foliage]].  As man began to eat foods easier to digest, they became less reliant on cellulose-rich plants for energy.<ref name="DescentOfMan" /><ref>{{cite news|title=The old curiosity shop|work=New Scientist|date=2008-05-17|url=https://www.newscientist.com/channel/being-human/mg19826562.100-vestigial-organs-remnants-of-evolution.html}}</ref>

== Reservoir of gut flora ==
Recent work shows the appendix is a safe place for useful [[bacteria]] when [[illness]] flushes those bacteria from the rest of the intestines.<ref name=health>Associated Press. [http://www.msnbc.msn.com/id/21153898/ "Scientists may have found appendix's purpose"]. [[MSNBC]], 5 October 2007. Accessed 17 March 2009.</ref><ref name="JTBpaper">{{Cite journal |last=Bollinger R.R. ''et al'' 2007 |title=Biofilms in the large bowel suggest an apparent function of the human vermiform appendix |journal=Journal of Theoretical Biology |year=2007 |volume=249 |issue=4 |pages=826–831 |doi=10.1016/j.jtbi.2007.08.032 |issn=0022-5193 |pmid=17936308}}</ref> This proposal is based on a new understanding of how the immune system supports the growth of beneficial [[gut flora]],<ref>{{Cite journal|author1=Sonnenburg J.L; Angenent L.T. & Gordon J.I. 2004 |title=Getting a grip on things: how do communities of bacterial symbionts become established in our intestine? |journal=Nat. Immunol. |year=2004 |volume=5 |issue=6 |pages=569–73 |pmid=15164016 |doi=10.1038/ni1079|s2cid=25672527 }}</ref><ref>{{Cite journal|author1=Everett M.L. ''et al'' 2004 |title=Immune exclusion and immune inclusion: a new model of host-bacterial interactions in the gut |journal=Clinical and Applied Immunology Reviews |year=2004 |volume=4 |pages=321–32 |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 more likely to have a recurrence of ''[[Clostridium difficile]]'' [[colitis]].<ref>{{cite web|url=https://blogs.scientificamerican.com/guest-blog/your-appendix-could-save-your-life/|title=Your Appendix Could Save Your Life|first=Rob|last=Dunn|website=Scientific American Blog Network}}</ref> The appendix, therefore, may act as a "safe house" for [[commensalism|commensal]] ("good") bacteria. This reservoir of gut flora could then serve to repopulate the digestive system following a bout of [[dysentery]] or [[cholera]].<ref>MBD July 22, 2013. Scientists finally discover the function of the human appendix. [http://politicalblindspot.com/scientists-finally-discover-the-function-of-the-human-appendix/] {{Webarchive|url=https://web.archive.org/web/20160916104721/http://politicalblindspot.com/scientists-finally-discover-the-function-of-the-human-appendix/|date=2016-09-16}}</ref>

== References ==
{{reflist}}
[[Category:Evolutionary biology]]
[[Category:Anatomy]]