Necrosis 39936 225464674 2008-07-13T20:54:52Z Genevalq 7470789 /* See also */ removed some unnecessary wikis; left gangrene {{toxicology}} '''Necrosis''' (in [[Greek language|Greek]] Νεκρός = "dead") is the name given to unnatural [[death]] of [[cell (biology)|cell]]s and living [[biological tissue|tissue]]. It begins with cell swelling, [[chromatin]] digestion, and disruption of the [[plasma membrane]] and [[organelle]] membranes. Late necrosis is characterized by extensive [[DNA]] [[hydrolysis]], vacuolation of the [[endoplasmic reticulum]], organelle breakdown, and cell [[lysis]]. The release of intracellular content after plasma membrane rupture is the cause of [[inflammation]] in necrosis. In contrast to [[apoptosis]], cleanup of cell debris by [[phagocyte]]s of the [[immune system]] is generally more difficult, as the disorderly death generally does not send [[signal transduction|cell signals]] which tell nearby phagocytes to [[phagocytosis|engulf]] the dying cell. This lack of signaling makes it harder for the [[immune system]] to locate and recycle dead cells which have died through necrosis than if the cell had undergone apoptosis. == Causes == There are many causes of necrosis including prolonged exposure to [[injury]], [[infection]], [[cancer]], [[infarction]], [[poisons]], and [[inflammation]]. Severe damage to one essential system in the cell leads to secondary damage to other systems, a so-called "cascade of effects." Necrosis can arise from lack of proper care to a wound site. Necrosis is accompanied by the release of special [[enzyme]]s, that are stored by [[lysosome]]s, which are capable of digesting cell components or the entire cell itself. The injuries received by the cell may compromise the lysosome membrane, or may initiate a disorganised chain reaction which causes the release in enzymes. Unlike [[apoptosis]], cells that die by necrosis may release harmful chemicals that damage other cells. In [[biopsy]], necrosis is halted by [[fixation (histology)|fixation]] or freezing. Many species of [[viper]] (e.g. [[rattlesnakes]] or [[Bothrops]]) produce [[venom]] which causes severe necrosis in snake-bite victims. Additionally, some spiders (eg the [[brown recluse]]) contain venom which may cause significant cutaneous injuries with tissue loss and necrosis. [[Image:Tissue necrosis following bite from Bothrops asper PLoS Medicine.jpg|thumb|left|Severe tissue necrosis following ''[[Bothrops asper]]'' envenomation. The victim was an 11-year old boy, bitten two weeks earlier in [[Ecuador]], but treated only with [[antibiotics]].<ref name="Nor-C&L04">Norris R. 2004. Venom Poisoning in North American Reptiles. ''In'' Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.</ref>]] ==Morphologic patterns== There are seven distinctive morphologic patterns of necrosis: * [[Coagulative necrosis]] is typically seen in [[hypoxia (medical)|hypoxic]] environments (e.g. [[myocardial infarction]], infarct of the [[spleen]]). Cell outlines remain after cell death and can be observed by light [[microscopy]]. * [[Liquefactive necrosis]] is usually associated with cellular destruction and [[pus]] formation (e.g. [[pneumonia]]). This is typical of bacterial or, sometimes, fungal infections because of their ability to stimulate an inflammatory reaction. Curiously, [[ischemia]] (restriction of blood supply) in the brain produces liquefactive rather than coagulative necrosis, this is due to the lack of any substantial supportive stroma. * [[Gummatous]] necrosis is restricted to necrosis involving [[spirochaetal]] infections (e.g. [[syphilis]]). * [[Haemorrhagic]] necrosis is due to blockage of the venous drainage of an organ or tissue (e.g. in [[testicular torsion]]). * [[Caseous necrosis]] is a specific form of coagulation necrosis typically caused by mycobacteria (e.g. [[tuberculosis]]). It can be considered a combination of coagulative and liquefactive necroses. * [[Fat]]ty necrosis results from the action of [[lipase]]s on fatty tissues (e.g. [[acute pancreatitis]], [[breast]] tissue necrosis). * [[Fibrinoid necrosis]] is caused by [[immune]]-mediated [[blood vessel|vascular]] damage. It is marked by deposition of [[fibrin]]-like [[protein]]aceous material in [[artery|arterial]] walls, which appears smudgy and [[eosinophilic]] on light microscopy. ===Arachnogenic necrosis=== [[Spider bite]]s are cited as causing necrosis in some areas. These claims are widely disputed. In the US at least, only the bites of spiders in the genus ''[[Loxosceles]]'' or brown recluse have been proven to consistently cause necrosis.<ref name="Science1957-Atkins">{{cite journal | author = Atkins J, Wingo C, Sodeman W | title = Probable cause of necrotic spider bite in the Midwest | journal = Science | volume = 126 | issue = 3263 | pages = 73 | year = 1957 | pmid = 13442644 | doi = 10.1126/science.126.3263.73 <!--Retrieved from CrossRef by DOI bot-->}}</ref> Many other spider species are claimed to cause necrosis but in most cases firm evidence is lacking. Partially this is because the early bite is often painless and the spider species cannot be identified. Several species of spiders possess toxins proven to cause necrosis: * ''Loxosceles'' spiders, including the [[brown recluse]] in the midwestern United States and the [[Chilean recluse]] in South America Spiders suspected of, but not shown to cause necrosis: * [[White-tailed spider]]s in [[Australia]] and [[New Zealand]]<ref name="MJA2003-Isbister">{{cite journal | author = Isbister G, Gray M | title = White-tail spider bite: a prospective study of 130 definite bites by Lampona species. | journal = Med J Aust | volume = 179 | issue = 4 | pages = 199–202 | year = 2003 | pmid = 12914510}}</ref> * [[Hobo spider]] in northwestern USA<ref name="Annemergmed2004-Vetter">{{cite journal | author = Vetter R, Isbister G | title = Do hobo spider bites cause dermonecrotic injuries? | journal = Ann Emerg Med | volume = 44 | issue = 6 | pages = 605–7 | year = 2004 | pmid = 15573036 | doi = 10.1016/j.annemergmed.2004.03.016 <!--Retrieved from CrossRef by DOI bot-->}}</ref> * [[Sac spider]] in United States and Australia<ref name="AmJTropMedHyg2006-Vetter">{{cite journal | author = Vetter R, Isbister G, Bush S, Boutin L | title = Verified bites by yellow sac spiders (genus Cheiracanthium) in the United States and Australia: where is the necrosis? | journal = Am J Trop Med Hyg | volume = 74 | issue = 6 | pages = 1043–8 | year = 2006 | pmid = 16760517}}</ref> ==See also== * [[Gangrene]] ==External links== * [http://www.omdict.com/definition/necrosis.php Necrosis causes, details and definition] ==Footnotes== {{reflist}} {{pathology}} [[Category:Death]] [[Category:Cellular processes]] [[bg:Некроза]] [[cs:Nekróza]] [[da:Nekrose]] [[de:Nekrose]] [[et:Nekroos]] [[es:Necrosis]] [[fr:Nécrose]] [[io:Nekroso]] [[it:Necrosi]] [[he:נקרוזה]] [[lt:Nekrozė]] [[hu:Nekrózis]] [[nl:Necrose]] [[ja:壊死]] [[pl:Martwica]] [[pt:Necrose]] [[ru:Некроз]] [[sk:Nekróza]] [[fi:Nekroosi]] [[sv:Nekros]] [[tr:Nekroz]] [[uk:Некроз]]