Vermiform appendix 99611 224844163 2008-07-10T17:49:23Z H.al-shawaf 1805093 /* Size and location */ add wiki link {{Infobox Anatomy | Name = Vermiform Appendix | Latin = appendix vermiformis | GraySubject = 249 | GrayPage = 1178 | Image = Gray536.png | Caption = Arteries of cecum and vermiform appendix. (Appendix visible at lower right, labeled as "vermiform process"). | Image2 = Stomach colon rectum diagram.svg | Caption2 = Normal location of the appendix relative to other organs of the digestive system (frontal view). | Precursor = [[Midgut]] | System = [[Gastrointestinal tract|Digestive]] | Artery = [[appendicular artery]] | Vein = [[appendicular vein]] | MeshName = Appendix | MeshNumber = A03.556.124.526.209.290 | DorlandsPre = a_54 | DorlandsSuf = 12147735 | }} In [[human anatomy]], the '''appendix''' (or '''vermiform appendix'''; also '''cecal (or caecal) appendix'''; also '''vermix''') is a blind ended tube connected to the [[cecum]] (or caecum), from which it develops [[embryo]]logically. The cecum is a pouch-like structure 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". ==Size and location== The appendix averages 10 cm in length, but can range from 2 to 20 cm. The diameter of the appendix is usually between 7 and 8 mm. The longest appendix ever removed measured 26 cm in [[Zagreb, Croatia]]. <ref name="record">[http://www.guinnessworldrecords.com/records/human_body/body_parts/largest_appendix_removed.aspx Guinness world record for longest appendix removed.]</ref> in the lower right quadrant of the [[abdomen]], or more specifically, the right [[iliac fossa]].<ref name="Surgery">Paterson-Brown S. The acute abdomen and intestinal obstruction. Chapter 15 in Garden O.J., Bradbury A.W., Forsythe J.L.R., Parks R.W. (2007) Principles and Practise of Surgery, Fifth Edition, Churchill Livingstone Elsevier.</ref> Its position within the abdomen corresponds to a point on the surface known as [[McBurney's point]] (see below). While the base of the appendix is at a fairly constant location, 2 cm below the [[ileocaecal valve]] <ref name="Surgery"/>, the location of the tip of the appendix can vary from being [[retrocaecal]] (74% <ref name="Surgery"/>) to being in the [[pelvis]] to being [[peritoneum|extraperitoneal]]. In rare individuals with [[situs inversus]], the appendix may be located in the lower left side. ==Function== Given the appendix's propensity to cause death via [[infection]], and the seemingly perfect health of those who have had their appendix removed, the biological purpose of the appendix has mystified scientists for some time. There have been cases of people who have been found, usually on [[laparoscopy]] or [[laparotomy]], to have a [[congenital]] absence of an appendix. There have been no reports of impaired [[immunity (medical)|immune]] or [[gastrointestinal]] function in these people. ====Vestigiality==== The most common explanation is that the appendix is a [[vestigial structure]] with no absolute purpose. In ''[http://onlinebooks.library.upenn.edu/webbin/gutbook/lookup?num=1043 The Story of Evolution]'', [[Joseph McCabe]] argued thus: <blockquote> The vermiform appendage—in which some recent medical writers have vainly endeavoured to find a utility—is the shrunken remainder of a large and normal intestine of a remote ancestor. This interpretation of it would stand even if it were found to have a certain use in the human body. Vestigial organs are sometimes pressed into a secondary use when their original function has been lost. </blockquote> One potential ancestral purpose put forth by [[Charles Darwin|Darwin]]<ref name="DescentOfMan">[[Charles Darwin|Darwin, Charles]] (1871). ''[[The Descent of Man, and Selection in Relation to Sex]]''. John Murray: London.</ref> was that the appendix was used for digesting leaves as [[primate]]s. Over time, we have eaten fewer [[vegetable]]s and have evolved, over millions of years, for this organ to be smaller to make room for our [[stomach]]. It may be a vestigial organ of ancient man that has degraded down to nearly nothing over the course of evolution. Evidence can be seen in herbivorous animals such as the Koala. The cecum of the koala is attached to the juncture of the small and large intestines and is very long, enabling it to host bacteria specific for cellulose breakdown. Early man’s ancestor must have also relied upon this system and lived on a diet rich in foliage. As man began to eat more easily digested foods, they became less reliant on cellulose-rich plants for energy. The cecum became less necessary for digestion and mutations that previously had been deleterious were no longer selected against. These alleles became more frequent and the cecum continued to shrink. After thousands of years, the once-necessary cecum has degraded to what we see today; the appendix. <ref name="DescentOfMan" /> Creationists quote<ref>{{cite web|url=http://www.answersingenesis.org/tj/v3/i1/appendix.asp|accessdate=2008-07-01|month=04|year=1988|title=The human vermiform appendix: A general surgeon’s reflections}}</ref> wrongly to claim that "Few [[mammals]] other than humans, the other anthropoid apes, and other primates have an appendix." even though the creationist website they quote refers only to a 'vermiform' appendix. Recent evidence based on a possible immune function is seen by one group of researchers to contradict the explanation of the appendix as a vestige of [[evolution|evolutionary]] development.<ref name=JTBpaper/> [[Image:Malpy waskonose s.png|right|thumb|The appendix is more developed in [[Old World monkey]]s.<ref>Fisher, R. E. (2000) "The primate appendix: a reassessment." Anat Rec. 261: 228-236. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11135184&dopt=Abstract PubMed]</ref>]] However, such a view is actually a misinterpretation of the claim of vestigial status in evolutionary theory (i.e., vestigial systems can have other functions). Evolutionary theorists have suggested that natural selection selects for larger appendices because smaller and thinner appendices would be more susceptible to inflammation and disease<ref>{{cite news|title=The old curiosity shop|work=[[New Scientist]]|date=2008-05-17|url=http://www.newscientist.com/channel/being-human/mg19826562.100-vestigial-organs-remnants-of-evolution.html}}</ref>. ====Immune Use==== Loren G. Martin, a professor of [[physiology]] at [[Oklahoma State University]], argues that the appendix has a function in [[human fetus|fetuses]] and adults.<ref>{{cite news|url=http://www.sciam.com/article.cfm?id=what-is-the-function-of-t|title=What is the function of the human appendix? Did it once have a purpose that has since been lost?|work=[[Scientific American]]|date=1999-10-21|accessdate=2008-07-01}}</ref> [[Endocrine system|Endocrine]] cells have been found in the appendix of 11 week old fetuses that contribute to "biological control ([[homeostasis|homeostatic]]) mechanisms." In adults, Martin argues that the appendix acts as a [[Lymphatic system|lymphatic]] organ. The appendix is experimentally verified as being rich in infection-fighting [[Lymphatic system|lymphoid cells]], suggesting that it might play a role in the [[immune system]]. Zahid<ref>Zahid, A. (2004) "The vermiform appendix: not a useless organ." J Coll Physicians Surg Pak. 14:256-258. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15228837&dopt=Abstract PubMed]</ref> suggests that it plays a role in both manufacturing [[hormone]]s in [[Prenatal development|fetal development]] as well as functioning to 'train' the immune system, exposing the body to [[antigens]] in order that it can produce [[antibody|antibodies]]. He notes that doctors in the last decade have stopped removing the appendix during other surgical procedures as a routine precaution, because it can be successfully transplanted into the [[Urinary system|urinary tract]] to rebuild a [[sphincter]] muscle and reconstruct a functional [[urinary bladder|bladder]]. [[Image:Appendix function diagram.svg|right|thumb|Apparent function of the human vermiform appendix in the recovery from diarrhea. Although more than 2 million children die each year in developing countries as a result of diarrhea, children living in those countries face an estimated 1.4 billion cases of diarrhea each year <ref> Data from the [[Centers for Disease Control and Prevention]] (CDC) as published in Emerg Infect Dis 9(5), 2003.)</ref> Thus, the process of recovery from diarrhea is relatively effective in developing countries. This process is expected to be less critical in developed countries, where widespread epidemics resulting in diarrhea are uncommon and thus the loss of beneficial bacteria from the population as a whole is highly unlikely.]] ====Latest Interpretation: Maintaining gut flora==== Although it was long accepted that the immune tissue, called [[gut associated lymphoid tissue]], surrounding the appendix and elsewhere in the gut carries out a number of important functions, explanations were lacking for the distinctive shape of the appendix and its apparent lack of importance as judged by an absence of side-effects following appendectomy. <ref name="PBD4thEd"> Robbins Pathologic Basis of Disease, 4th edition, 1989, pages 902-903 </ref> William Parker, Randy Bollinger, and colleagues at [[Duke University]] proposed that the appendix serves as a safe haven for useful [[bacteria]] when illness flushes those bacteria from the rest of the intestines.<ref>{{cite news|url=http://www.msnbc.msn.com/id/21153898/|title=Scientists may have found appendix’s purpose: Seemingly useless organ may produce, protect good germs for your gut|date=2007-10-05|accessdate=2008-07-01|work=[[MSNBC]]}}</ref> <ref name="JTBpaper">Bollinger, R.R., Barbas, A.S., Bush, E.L., Lin, S.S. & Parker. W. (2007) Biofilms in the large bowel suggest an apparent function of the human vermiform appendix. J. Theoretical Biology. doi:10.1016/j.jtbi.2007.08.032.</ref> This proposal is based on a new understanding of how the immune system supports the growth of beneficial [[gut flora|intestinal bacteria]] <ref> Sonnenburg JL, LT Angenent, JI Gordon. Getting a grip on things: how do communities of bacterial symbionts become established in our intestine? Nature Immunology. 2004;5:569-73 </ref> <ref> Everett ML, D Palestrant, SE Miller, RR Bollinger, W Parker. Immune exclusion and immune inclusion: a new model of host-bacterial interactions in the gut. Clinical and Applied Immunology Reviews. 2004;5:321-332. </ref>, in combination with many well-known features of the appendix, including its architecture and its association with copious amounts of immune tissue. Such a function is expected to be useful in a culture lacking modern sanitation and healthcare practice, where [[diarrhea]] may be prevalent.<ref name="JTBpaper"/> Current [[epidemiology|epidemiological]] data <ref> Statistics on the cause of death in developed countries collected by the [[World Health Organization]] in 2001 show that acute diarrhea is the fourth leading cause of disease-related death in developing countries (data summarized by The Bill and Melinda Gates Foundation).{{Fact|date=December 2007}} Two of the other leading causes of death are expected to have exerted limited or no selection pressure on humans in the distant past because one (HIV-AIDS) only very recently emerged and another (ischaemic heart disease) primarily affects people in their post-reproductive years. Thus, acute diarrhea may have been one of the primary disease-related selection pressures on the human population in the past. (Lower respiratory tract infection (pneumonia) is the remaining of the top four leading causes of disease-related death in third world countries.) </ref> show that diarrhea is one of the leading causes of death in [[Developing country|developing countries]], indicating that a role of the appendix as an aid in recovering beneficial bacteria following diarrhea may be extremely important in the absence of modern health and sanitation practices.<ref name="JTBpaper"/> ==Diseases== {{Refimprove|section|date=April 2007}} The most common [[disease]]s of the appendix (in humans) are [[appendicitis]] and [[carcinoid]] tumors. [[Appendix cancer]] accounts for about 1 in 200 of all gastrointestinal malignancies. [[Adenomas]] also (rarely) present. [[Appendicitis]] (or epityphlitis) is a condition characterized by [[inflammation]] of the appendix. Virtually all cases of appendicitis require removal of the inflamed appendix, either by [[laparotomy]] or [[laparoscopy]]. Untreated, the appendix may rupture, leading to [[peritonitis]], then shock, and, if continued untreated, death. Pain often begins in the center of the abdomen where the lining of the stomach is irritated then moves lower right as the condition develops; it is important to note that this makes diagnoses difficult in the early stages because an [[magnetic resonance imaging|MRI]] or [[Computed tomography|CT]] scan must be used to detect it. Appendicitis presents as pain in the right lower quadrant with [[rebound tenderness]] (pain upon ''removal'' of pressure rather than ''application'' of pressure). In particular, it presents at [[McBurney's point]], 1/3 of the way along a line drawn from the [[Anterior Superior Iliac Spine]] to the [[Navel|Umbilicus]]. Typically, point (skin) pain is not present until the [[parietal peritoneum]] is inflamed as well. Fever and immune system response are also characteristic of appendicitis. The surgical removal of the vermiform appendix is called an [[appendicectomy]] (or appendectomy). This procedure is normally performed as an emergency procedure, when the patient is suffering from [[Acute (medical)|acute]] appendicitis. In the absence of surgical facilities, [[intravenous]] [[antibiotics]] are used to delay or avoid the onset of [[sepsis]]; it is now recognized that many cases will resolve when treated non-operatively. In some cases the appendicitis resolves completely; more often, an inflammatory mass forms around the appendix. This is a relative contraindication to surgery. ==Use as efferent urinary conduit== The appendix is used for the construction of an efferent urinary conduit, in an operation known as the [[Mitrofanoff procedure]],<ref name=mingin>{{cite journal |author=Mingin GC, Baskin LS |title=Surgical management of the neurogenic bladder and bowel |journal=Int Braz J Urol |volume=29 |issue=1 |pages=53–61 |year=2003 |pmid=15745470 |doi= |url=http://www.brazjurol.com.br/january_february_2003/Baskin_ing_53_61.htm}}</ref> in people with a [[neurogenic bladder]]. ==Additional image== <gallery> Image:Appendixcancer.gif|Mucinous adenocarcinoma of the appendix tip </gallery> ==See also== {{Commons}} * [[Homology (biology)]] * [[McBurney's point]] ==References== {{reflist}} ==External links== *[http://www.talkorigins.org/faqs/vestiges/appendix.html "The vestigiality of the human vermiform appendix: A Modern Reappraisal"] -- [[evolutionary biology]] argument that the appendix is vestigial *[http://www.cnn.com/2007/HEALTH/10/05/appendix.purpose.ap/index.html Purpose of appendix believed found] CNN article *[http://www.webmd.com/digestive-disorders/news/20071012/appendix-may-have-purpose Appendix May Actually Have a Purpose] WebMD article * {{SUNYAnatomyLabs|37|12|01|02}} - "Abdominal Cavity: The Cecum and the Vermiform Appendix" {{digestive system}} [[Category:Organs]] [[Category:Digestive system]] [[ar:زائدة دودية]] [[bn:অ্যাপেন্ডিক্স]] [[cs:Apendix]] [[de:Appendix vermiformis]] [[es:Apéndice vermiforme]] [[eo:Apendico]] [[fr:Appendice iléo-cæcal]] [[id:Umbai cacing]] [[it:Appendice vermiforme]] [[he:תוספתן]] [[jv:Umbai cacing]] [[la:Appendix vermiformis]] [[lt:Kirmėlinė atauga]] [[ms:Apendiks]] [[nl:Wormvormig aanhangsel]] [[ja:虫垂]] [[pl:Wyrostek robaczkowy]] [[pt:Apêndice vermiforme]] [[ru:Аппендикс]] [[sl:Slepič]] [[sh:Slepo crevo]] [[fi:Umpilisäke]] [[te:ఉండుకము]] [[tr:Apandis]] [[uk:Апендикс]] [[zh:阑尾]]