necrosis


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necrosis

1. the death of one or more cells in the body, usually within a localized area, as from an interruption of the blood supply to that part
2. death of plant tissue due to disease, frost, etc.

Necrosis

 

the death within the living organism of individual organs or their component tissues or cells.

A necrosis is classified according to the pathological condition that causes it. Thus, frostbite and burns can cause traumatic necrosis; neurotropic necrosis arises with syringomyelia and the nervous form of leprosy; infarcts and gangrene are associated with circulatory, or ischemic, necrosis; caseous necroses occurring in tuberculosis and syphilis are forms of septic necrosis; and fibrinoid necrosis associated with allergic diseases is a type of allergic necrosis.

Necrosis is accompanied by characteristic changes in the cell and in the intercellular substances. The nucleus shrinks and coagulates, a process known as pycnosis, and the cytoplasm breaks up into clumps. The cell eventually lyses, that is, it degenerates and dissolves. The lysis is due to the activation of the lysosomal hydrolytic enzymes, such as ribonuclease, deoxyribonuclease, and acid phosphatase. The activation of the lysosomes occurs as a result of an increase in the permeability of the cell membranes, changes in the osmotic equilibrium, and acidosis—an abnormal increase in the intracellular hydrogen-ion concentration. Fibrinoid changes appear in the connective tissue, and nerve fibers become fragmented and disintegrate into clumps.

The clinical and morphological manifestations and further consequences of necrosis depend on the localization and distribution of the necrosis and on the mechanisms and conditions of origin. The following types of advanced necrotic conditions can develop: dry necrosis, such as Zenker’s degeneration of infected muscles; colliquative, or liquefactive, necrosis, which occurs for example, when a focus of softening arises in the brain in response to cerebral hemorrhage; gangrene; and bed sores. Necrotic tissue tears away; then, either connective tissue grows through it or the necrotic tissue undergoes autolytic or purulent liquefaction. Finally, the necrotic tissue becomes encapsulated and petrified.

The two most serious consequences of necrosis are a loss of function owing to the death of the structural elements of the necrotic tissues or organs and poisoning caused by the actual presence of a necrotic focus and by the inflammation that arises in response to this presence.

V. V. SEROV

necrosis

[nə′krō·səs]
(medicine)
Death of a cell or group of cells as a result of injury, disease, or other pathologic state.
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New reconstructive surgery for penile paraffinoma to prevent necrosis of ventral penile skin.
Abdominal fat necrosis falls into 4 recognized categories: nutritional, enzymatic necrosis associated with pancreatitis, traumatic necrosis, and idiopathic massive fat necrosis of cattle.
Although fat necrosis may exhibit a varied appearance on breast MRI, the most common presentation is that of a lipid cyst, which appears as a round or oval mass with a hypointense Tl signal on fat-saturated images.
Indolent granulomatous necrosis in patients with previous tubal diathermy.
The first case was reported in 1983 as an isolated necrosis of the epiglottis in a 21 year old female with lymphoid leukaemia (2).
Bunchstem necrosis can appear very early in fruit development (around bloom) or after veraison.
Modulation of tumor necrosis factor-alpha and oxidative stress through protein kinese C and P42/44 mitogen-activated protein kinase in lead increases lipopolysaccharide-induced liver damage in rats.
Within a few days, multiple small, well-circumscribed areas of skin necrosis around the fingerprick sites quickly progressed to full necrosis of the distal phalange, despite treatment with iloprost infusions, the investigators said (Lancet 2004;364:980).
Necrosis of the digits was the initial manifestation in five patients and eventually developed in a total of 15.
Avascular necrosis set in, and Carter underwent a second hip surgery Nov.
Hyperbaric oxygen: a new adjunct in the management of radiation necrosis.
CHICAGO -- Smoking may be a risk factor for development of avascular necrosis in HIV-infected patients, Dr.