Necrosis

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Necrosis

Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


Necrosis (in Greek Νεκρός = Dead) is the name given to accidental death of cells and living tissue.

Necrosis is less orderly than apoptosis, which is part of programmed cell death. In contrast apoptosis, cleanup of cell debris by phagocytes of the immune system is generally more difficult, as the disorderly death generally does not send cell signals which tell nearby phagocytes to engulf the dying cell. This lack of signalling 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. The release of intracellular content after cellular membrane damage is the cause of inflammation in necrosis.

Causes

There are many causes of necrosis including prolonged exposure to injury, infection, cancer, infarction, poisons, bites from some spiders such as brown recluses 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 enzymes, that are stored by lysosomes, 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 an unorganized 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 or freezing.

Morphologic patterns

There are seven distinctive morphologic patterns of necrosis:

Arachnogenic necrosis

Spider bites 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.[1] Many other spider species are claimed to cause necrosis but in most cases firm evidence is lacking, partially because the early bite is often painless and the spider species seldom identified and because a common reaction by doctors to a possible necrotic spider bite is to remove the flesh pre-emptively.

Several species of spiders possess toxins proven to cause necrosis:

Spiders suspected of, but not shown to cause necrosis:

References

  1. Atkins J, Wingo C, Sodeman W (1957). "Probable cause of necrotic spider bite in the Midwest". Science. 126 (3263): 73. PMID 13442644. doi:10.1126/science.126.3263.73. 
  2. Maynor ML, Moon RE, Klitzman B, Fracica PJ, Canada A (1997). "Brown recluse spider envenomation: a prospective trial of hyperbaric oxygen therapy". Acad Emerg Med. 4 (3): 184–92. PMID 9063544.  Unknown parameter |month= ignored (help)
  3. Maynor ML, Abt JL, Osborne PD (19892). "Brown Recluse Spider Bites: Beneficial Effects of Hyperbaric Oxygen". J. Hyperbaric Med. 7 (2): 89–102. ISSN 0884-1225. Retrieved 2008-07-25.  Check date values in: |date= (help)
  4. Isbister G, Gray M (2003). "White-tail spider bite: a prospective study of 130 definite bites by Lampona species.". Med J Aust. 179 (4): 199–202. PMID 12914510. 
  5. Vetter R, Isbister G (2004). "Do hobo spider bites cause dermonecrotic injuries?". Ann Emerg Med. 44 (6): 605–7. PMID 15573036. doi:10.1016/j.annemergmed.2004.03.016. 
  6. Vetter R, Isbister G, Bush S, Boutin L (2006). "Verified bites by yellow sac spiders (genus Cheiracanthium) in the United States and Australia: where is the necrosis?". Am J Trop Med Hyg. 74 (6): 1043–8. PMID 16760517. 

See also


bg:Некроза

cs:Nekróza da:Nekrose de:Nekrose et:Nekroosio:Nekroso it:Necrosi he:נקרוזה lt:Nekrozė hu:Nekrózis nl:Necrosesk:Nekróza sv:Nekrosuk:Некроз


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