- Pathologic death of one or more cells, or of a portion of tissue or organ, resulting from irreversible damage; earliest irreversible changes are mitochondrial, consisting of swelling and granular calcium deposits seen by electron microscopy; most frequent visible alterations are nuclear : pyknosis, shrunken and abnormally dark basophilic staining; karyolysis, swollen and abnormally pale basophilic staining; or karyorrhexis, rupture and fragmentation of the nucleus. After such changes, the outlines of individual cells are indistinct, and affected cells may become merged, sometimes forming a focus of coarsely granular, amorphous, or hyaline material. [G. nekrosis, death, fr. nekroo, to make dead]- acute massive liver n. a lesion in which there is extensive and rapid death of parenchymal cells of the liver, sometimes with fatty degeneration of the size of the organ; the n. may result from fulminant viral infection or chemical poisoning; associated with jaundice. SYN: acute parenchymatous hepatitis, acute yellow atrophy of the liver, Rokitansky disease (1).- acute retinal n. (ARN) a viral syndrome occurring in immunocompetent patients, characterized by peripheral retinal destruction that becomes circumferential and leads to retinal detachment.- bridging hepatic n. area of liver n. that bridges adjacent portal areas and central veins; subsequent postnecrotic collapse and fibrosis is likely to result in cirrhosis.- caseous n., caseation n. n. characteristic of certain inflammations ( e.g., tuberculosis, histoplasmosis), which represents n. with loss of separate structures of the various cellular and histologic elements; affected tissue manifests the friable, crumbly consistency and dull, opaque quality observed in cheese. SYN: caseous degeneration.- coagulation n. a type of n. in which the affected cells or tissue are converted into a dry, dull, fairly homogeneous eosinophilic mass without nuclear staining, as a result of the coagulation of protein as occurs in an infarct; microscopically, the necrotic process involves chiefly the cells, and remnants of histologic elements ( e.g., elastin, collagen, muscle fibers) may be recognizable, as well as “ghosts” of cells and portions of cell membranes; may be caused by heat, ischemia, and other agents that destroy tissue, including enzymes that would continue to alter the devitalized cellular substance.- cystic medial n. loss of elastic and muscle fibers in the aortic media, with accumulation of mucopolysaccharide, sometimes in cystlike spaces between the fibers; a disease of unknown cause, which may be inherited and which predisposes to dissecting aneurysms. SYN: Erdheim disease, medionecrosis aortae idiopathica cystica, medionecrosis of the aorta, mucoid medial degeneration.- epiphysial aseptic n. aseptic n. of bony epiphyses in children or adults probably due to ischemia; it may affect the upper end of the femur (Legg-Calvé-Perthes disease), the tibial tubercle (Osgood-Schlatter disease), the tarsal navicular bone or the patella (Köhler disease), the second metatarsal head (Freiberg disease), vertebral bodies (Scheuermann disease), or the capitellum of the humerus (Panner disease).- fat n. the death of adipose tissue, characterized by the formation of small (1–4 mm), dull, chalky, gray or white foci; these represent small quantities of calcium soaps formed in the affected tissue when fat is hydrolyzed into glycerol and fatty acid s. SYN: steatonecrosis.- fibrinoid n. n. in which the necrotic tissue has some staining reactions resembling fibrin and becomes deeply eosinophilic, homogenous, and refractile.- focal n. occurrence of numerous, relatively small or tiny, fairly well-circumscribed, usually spheroidal portions of tissue that manifest coagulative, caseous, or gummatous n. and are characteristically associated with agents that are hematogenously disseminated; frequently observed only in histologic sections, but the foci may be as large as 1–3 mm and macroscopically visible; arbitrarily, foci larger than that are usually not termed focal n..- ischemic n. n. caused by hypoxia resulting from local deprivation of blood supply, as by infarction.- laminar cortical n. the breaking down of a definite cell layer in the cerebral cortex, encountered typically after temporary cardiac arrest or perinatal hypoxia.- liquefactive n. a type of n. characterized by a fairly well-circumscribed, microscopically or macroscopically visible lesion that consists of the dull, opaque or turbid, gray-white to yellow-gray, soft or boggy, partly or completely fluid remains of tissue that became necrotic and was digested by enzymes, especially proteolytic enzymes liberated from disintegrating leukocytes; it is classically observed in abscesses, and frequently in infarcts of the brain.- progressive outer retinal n. (PORN) a viral syndrome occurring in AIDS patients, caused by herpesvirus and characterized by destruction of peripheral retina.- renal papillary n. n. of renal papillae, occurring in acute pyelonephritis, especially in diabetics, or in analgesic nephropathy; renal failure may result. SYN: necrotizing papillitis.- simple n. a stage of coagulation n.; the occurrence of a coarsely granular or hyaline change in the cytoplasm, and the lack of a recognizable nucleus, with the general configuration of the dead cells being relatively unchanged.- subcutaneous fat n. of newborn indurated plaques and nodules appearing usually a few days or a few weeks after birth and usually resolving within a few months, characterized microscopically by birefringent needle-shaped crystals within necrotic fat cells; the condition remains localized, unlike sclerema neonatorum, although hypercalcemia may develop.- total n. 1. complete n. of the cytologic and histologic elements in a portion of tissue, as in caseous n.; 2. death of an entire organ or part.- zonal n. n. predominantly affecting or limited to an anatomical zone, especially parts of the hepatic lobules defined according to proximity to either the portal tracts or central (hepatic) veins.
* * *ne·cro·sis nə-'krō-səs, ne- n, pl ne·cro·ses -.sēz death of living tissue specif death of a portion of tissue differentially affected by local injury (as loss of blood supply, corrosion, burning, or the local lesion of a disease) compare NECROBIOSIS
* * *n.the death of some or all of the cells in an organ or tissue, caused by disease, physical or chemical injury, or interference with the blood supply (see gangrene). Caseous necrosis occurs in pulmonary tuberculosis, the lung tissue becoming soft, dry, and cheeselike.
* * *ne·cro·sis (nə-kroґsis) pl. necroґses [Gr. nekrōsis deadness] the sum of the morphological changes indicative of cell death and caused by the progressive degradative action of enzymes; it may affect groups of cells or part of a structure or an organ. necrotic adj
Medical dictionary. 2011.