A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response. More information: In technical terms, the inflammatory response directs immune system components to the site of injury or infection and is manifest by increased blood supply and vascular permeability which, in technical terms, allows chemotactic peptides, neutrophils, and mononuclear cells to leave the intravascular compartment. Microorganisms are engulfed by phagocytic cells (e.g., neutrophils and macrophages) in an attempt to contain the infection in a small-tissue space. The response includes attraction of phagocytes in a chemotactic gradient of microbial products, movement of the phagocyte to the inflammatory site and contact with the organism, phagocytosis (ingestion) of the organism, development of an oxidative burst directed toward the organism, fusion of the phagosome and lysosome with degranulation of lysosomal contents, and death and degradation of the organism. When quantitative or qualitative defects in neutrophil function result in infection, the infection usually is prolonged and recurrent and responds slowly to antimicrobial agents. Staphylococci, gram-negative organisms, and fungi are the usual pathogens responsible for these infections. History: Since antiquity (and to every medical student), the defining clinical features of inflammation have been known in Latin as rubor (redness), calor (warmth), tumor (swelling) and dolor (pain). These hallmarks of inflammation were first described by Celsus — Aulus (Aurelius) Cornelius, a Roman physician and medical writer, who lived from about 30 B.C. to 45 A.D.
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A fundamental pathologic process consisting of a dynamic complex of cytologic and chemical reactions that occur in the affected blood vessel s and adjacent tissues in response to an injury or abnormal stimulation caused by a physical, chemical, or biologic agent, including: 1) the local reactions and resulting morphologic changes, 2) the destruction or removal of the injurious material, 3) the responses that lead to repair and healing. The so-called “cardinal signs” of i. are: rubor, redness; calor, heat (or warmth); tumor, swelling; and dolor, pain; a fifth sign, functio laesa, inhibited or lost function, is sometimes added. All of the signs may be observed in certain instances, but no one of them is necessarily always present. [L. inflammo, pp. -atus, fr. in, in, + flamma, flame]
- active i. SYN: acute i..
- acute i. any i. that has a fairly rapid onset, quickly becomes severe, and is usually manifested for only a few days, but which may persist for even a few weeks; characterized histologically by edema, hyperemia, and inflitrates of polymorphonuclear leukocytes. SYN: active i..
- adhesive i. i. in which the amount of fibrin in the exudate is sufficient to result in a slight or moderate degree of adherence of adjacent tissues, as in healing by first intention.
- allergic i. allergic reaction.
- alterative i. a local reaction to injury, occasionally observed in the walls of blood vessel s and in parenchymal cells of various organs in reacting to certain chemicals, viruses, and other intracellular agents; the response is characterized by degenerative changes in the cytoplasm and nucleus, frequently resulting in necrosis, but exudation (if any) is ordinarily observed only in the wall of the affected vessel, or in the interstices immediately adjacent to the affected vessel or parenchymal cells. SYN: degenerative i..
- atrophic i. a form of chronic i. or repeated episodes of acute i. in which the continued or recurrent proliferation of fibroblasts results in the formation of fibrous tissue that eventually contracts and leads to compression and atrophy of parenchymal tissue. SYN: fibroid i..
- catarrhal i. obsolete term for an inflammatory process that is most frequent in the respiratory tract, but may occur in any mucous membrane, and is characterized by hyperemia of the mucosal vessels, edema of the interstitial tissue, enlargement of the secretory epithelial cells (which proliferate and form conspicuous globules of mucus), and an irregular layer of viscous, mucinous material on the surface; as exudation progresses, variable numbers of neutrophils migrate into the affected tissue and are included in the exudate, along with fragments of degenerated and necrotic epithelial cells; such an i. may frequently become mucopurulent.
- chronic i. an i. that may begin with a relatively rapid onset or in a slow, insidious, and even unnoticed manner, and which tends to persist for several weeks, months, or years and has a vague and indefinite termination; occurs when the injuring agent (or products resulting from its presence) persists in the lesion, and the host's tissues respond in a manner (or to a degree) that is not sufficient to overcome completely the continuing effects of the injuring agent; characterized histopathologically by infiltrates of lymphocytes, plasma cells, and histiocytes; fibrosis; and granuloma formation.
- chronic active i. the coexistence of chronic i. and superimposed acute i..
- degenerative i. SYN: alterative i..
- exudative i. i. in which the conspicuous or distinguishing feature is an exudate, which may be chiefly serous, serofibrinous, fibrinous, or mucous ( e.g., relatively few cells are present), or may be characterized by relatively large numbers of neutrophils, eosinophils, lymphocytes, monocytes, or plasma cells, frequently with one or two types being predominant; it occurs not only as a separate and distinct pathologic process, but also frequently as a part of certain granulomatous inflammations.
- fibrinopurulent i. a purulent i. in which the exudate contains an unusually large amount of fibrin; also, a fibrinous or serofibrinous i. in which the accumulation of large numbers of polymorphonuclear leukocytes results in liquefactive necrosis of tissue and the formation of pus with a relatively large quantity of fibrin.
- fibrinous i. an exudative i. in which there is a disproportionately large amount of fibrin.
- fibroid i. SYN: atrophic i..
- granulomatous i. a form of proliferative i. SEE ALSO: granuloma.
- immune i. allergic reaction.
- interstitial i. i. in which the inflammatory reaction occurs chiefly in the supportive fibrous connective tissue or stroma of an organ.
- necrotic i., necrotizing i. usually an acute inflammatory reaction in which the predominant histologic change is fairly rapid necrosis that occurs diffusely or extensively in relatively large foci throughout the affected tissue, frequently with only little or no evidence of cells in the exudate.
- productive i. a vague term ordinarily used with reference to proliferative i., with or without an exudate; also sometimes used to indicate any i. in which grossly visible exudate is formed.
- proliferative i. an inflammatory reaction in which the distinguishing feature is an actual increase in the number of tissue cells, especially the reticuloendothelial macrophages, in contrast to cells exuded from blood vessel s; in addition, exudates of various types are likely to be observed in granulomas and other forms of proliferative i., but the latter may occur without an exudate being formed (as in certain infections caused by virus). SYN: hyperplastic i..
- pseudomembranous i. a form of exudative i. that involves mucous and serous membranes; relatively large quantities of fibrin in the exudate result in a rather tenacious membrane-like covering that is fairly adherent to the underlying acutely inflamed tissue; the pseudomembrane usually contains (in addition to the dense network of fibrin) varying quantities of plasma protein, degenerated and necrotic elements from the affected tissue, polymorphonuclear leukocytes, bacteria, etc.
- purulent i. an acute exudative i. in which the accumulation of polymorphonuclear leukocytes is sufficiently great that their enzymes cause liquefaction of the affected tissues, focally or diffusely; the purulent exudate is frequently termed pus, and consists of plasma and its constituents, end products of the enzymatic digestion of tissue, degenerated and necrotic cells and their debris, polymorphonuclear leukocytes and other white blood cells, the causal agent of the i., etc. SYN: suppurative i..
- sclerosing i. i. leading to extensive formation of fibrous and scar tissue.
- serofibrinous i. i. in which the exudate consists chiefly of serous fluid with an unusually large proportion of fibrin.
- serous i. an exudative i. in which the exudate is predominantly fluid ( e.g., exuded from the blood vessel s), with the protein, electrolytes, and other material contained therein; relatively few (if any) cells are observed.
- subacute i. an i. that is intermediate in duration between that of an acute i. and that of a chronic i., usually persisting longer than 3 or 4 weeks.
- suppurative i. SYN: purulent i..

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in·flam·ma·tion .in-flə-'mā-shən n a local response to cellular injury that is marked by capillary dilatation, leukocytic infiltration, redness, heat, pain, swelling, and often loss of function and that serves as a mechanism initiating the elimination of noxious agents and of damaged tissue

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the body's response to injury, which may be acute or chronic. Acute inflammation is the immediate defensive reaction of tissue to any injury, which may be caused by infection, chemicals, or physical agents. It involves pain, heat, redness, swelling, and loss of function of the affected part. Blood vessels near the site of injury are dilated, so that blood flow is locally increased. White blood cells enter the tissue and begin to engulf bacteria and other foreign particles. Similar cells from the tissues (see macrophage) remove and consume the dead cells, sometimes with the production of pus, enabling the process of healing to commence. In certain circumstances healing does not occur and chronic inflammation ensues.

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in·flam·ma·tion (in″flə-maґshən) [L. inflammare to set on fire] a localized protective response elicited by injury or destruction of tissues, which serves to destroy, dilute, or wall off (sequester) both the injurious agent and the injured tissue. It is characterized in the acute form by the classical signs of pain (dolor), heat (calor), redness (rubor), swelling (tumor), and loss of function (functio laesa). Histologically, it involves a complex series of events, including dilatation of arterioles, capillaries, and venules, with increased permeability and blood flow; exudation of fluids, including plasma proteins; and leukocytic migration into the inflammatory focus.

Medical dictionary. 2011.

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