Necrosis

Information about Necrosis

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:

Coagulative necrosis is typically seen in 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.
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).
Fatty necrosis results from the action of lipases on fatty tissues (e.g. acute pancreatitis, breast tissue necrosis).
Fibrinoid necrosis is caused by immune-mediated vascular damage. It is marked by deposition of fibrin-like proteinaceous material in arterial walls, which appears smudgy and eosinophilic on light microscopy.

| volume = 126 | issue = 3263 | pages = 73 | year = 1957 | id = PMID 13442644}} 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.

Spiders 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 spiders in Australia and New Zealand^[1]
Hobo spider in northwestern USA^[2]
Sac spider in United States and Australia^[3]

Footnotes

1. ^ 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.
2. ^ Vetter R, Isbister G (2004). "Do hobo spider bites cause dermonecrotic injuries?". Ann Emerg Med 44 (6): 605-7. PMID 15573036.
3. ^ 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.

• • [ e] Pathology
Principles of pathology	Disease - Necrosis - Infection - Ischemia - Inflammation - Wound healing - Neoplasia
Anatomical pathology	Surgical pathology - Cytopathology - Autopsy - Molecular pathology - Forensic pathology - Dental pathology Gross examination - Histopathology - Immunohistochemistry - Electron microscopy - Immunofluorescence - Fluorescent in situ hybridization
Clinical pathology	Clinical chemistry - Hematopathology - Transfusion medicine - Medical microbiology - Diagnostic immunology Enzyme assay - Mass spectrometry - Chromatography - Flow cytometry - Blood bank - Microbiological culture - Serology

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Death is the permanent end of the life of a biological organism. Death may refer to the end of life as either an event or condition.^[1] Many factors can cause or contribute to an organism's death, including predation, disease, habitat destruction, senescence,
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Biological tissue is a collection of interconnected cells that perform a similar function within an organism.

The study of tissue is known as histology, or, in connection with disease, histopathology.
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Apoptosis (pronounced ă-pŏp-tŏ’sĭs, apo tō' sis) is a form of programmed cell death in multicellular organisms. It is one of the main types of programmed cell death (PCD), and involves an orchestrated series of biochemical events leading to a
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Programmed cell-death (PCD) is the suicide of a cell in a multicellular organism. In contrast to necrosis, which is a form of cell-death that results from acute tissue injury and provokes an inflammatory response, PCD
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A phagocyte is a cell that ingests and destroys foreign matter such as microorganisms or debris by a process known as phagocytosis.

Types of Phagocytes

There are three main categories of phagocytes: ^[1]

macrophages (and monocytes)

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immune system is a collection of mechanisms within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy
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In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes, activated by second messengers resulting in
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Phagocytosis is the cellular process of engulfing solid particles by the cell membrane to form an internal phagosome, or "food vacuole." The phagosome is usually delivered to the lysosome, an organelle involved in the breakdown of cellular components, which fuses with the
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Injury is damage or harm caused to the structure or function of the body caused by an outside or force, which may be physical or chemical. Injury may also refer to injured feelings or reputation rather than injuries to the body.
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An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply (usually at the expense of the host).
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In medicine, an infarction is the process resulting in a macroscopic area of necrotic tissue in some organ caused by loss of adequate blood supply. Supplying arteries may be blocked from within by some obstruction (e.g.
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poisons are substances that can cause damage, illness, or death to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism.
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L. reclusa

Binomial name
Loxosceles reclusa
Gertsch & Mulaik, 1940

The brown recluse spider, Loxosceles reclusa
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Inflammation (Latin, inflammatio, to set on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants.
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Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.^[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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Lysosomes are organelles that contain digestive enzymes (acid hydrolases). They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. The membrane surrounding a lysosome prevents the digestive enzymes inside from destroying the cell.
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A biopsy (in Greek: bios = life and opsy = look/appearance) is a medical test involving the removal of cells or tissues for examination. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically (for example, using
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In the fields of histology, pathology, and cell biology, fixation is a chemical process by which biological tissues are preserved from decay. Fixation terminates any ongoing biochemical reactions, and may also increase the mechanical strength or stability of the treated tissues.
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Coagulation is a complex process by which blood forms solid clots. It is an important part of hemostasis (the cessation of blood loss from a damaged vessel) whereby a damaged blood vessel wall is covered by a platelet- and fibrin-containing clot to stop bleeding and begin repair of
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For other uses of the term "hypoxia", see hypoxia.

Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply.
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Myocardial infarction
Classification & external resources

Diagram of a myocardial infarction (2) of the tip of the anterior wall of the heart (an apical infarct
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The spleen is an organ located in the abdomen of the human body, where it functions in the destruction of old red blood cells and holding a small reservoir of blood. It is regarded as one of the centers of activity of the reticuloendothelial system (part of the immune system).
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Microscopy is any technique for producing visible images of structures or details too small to otherwise be seen by the human eye, using a microscope or other magnification tool. It is often used more specifically as a technique of using a microscope.
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A type of necrosis which is characteristic of focal bacterial or fungal infections. In liquefactive necrosis, the affected cell is completely digested due to powerful hydrolytic enzymes. It may be due to the increased activities of white blood cells which are attracted by the infections.
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Pus is a whitish-yellow or yellow substance produced during inflammatory responses of the body that can be found in regions of pyogenic bacterial infections. An accumulation of pus in an enclosed tissue space is known as an abscess.
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