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.
References in periodicals archive ?
In the 33 cases where coagulative necrosis was found the lesions were of varied size, in different evolutive stages and disseminated through the white and gray matter.
Similarly the histological abnormalities observed in kidneys of fish, treated with combination of copper sulphate and lead nitrate showed extravasation of blood from blood vessels; coagulative necrosis of first and second proximal segments, irregular blood congestion, and tubular necrosis (Fig.
The system is designed for outpatient treatments that achieve prostate reduction through coagulative necrosis of the heated tissue and subsequent resorption of this tissue over several weeks.
Granulomas may occasionally exhibit focal coagulative necrosis .
The histologic features that are considered helpful in identifying malignant myoepitheliomas include cellular atypia, coagulative necrosis, frequent mitotic figures, and tumor infiltration into adjacent tissue.
There were areas of coagulative necrosis (Figure 2B), sometimes with mineralization foci; loss of adhesion of the cells characterized the tubulo-papillary main aspect of the neoplasm.
Foci of coagulative necrosis were present, resulting in a vaguely granulomatous appearance (Figure 1, B).
There was only a very rare mitotic figure and no coagulative necrosis present.
5) Also identified were several zones of coagulative necrosis.
Low-power magnification of an EMC reveals lobular, pushing borders and coagulative necrosis in the center of the lobules.
Hematoxylin-eosin-stained and Movat-stained sections demonstrated a rounded infarct composed of coagulative necrosis that was well demarcated from the surrounding intact lung parenchyma by a zone of epithelioid histiocytes and fibrous connective tissue.
Greater morbidity and mortality appear to be associated with tumors larger than 6 cm, intraabdominal tumors, a lack of postoperative adjuvant therapy, and the presence of coagulative necrosis, a high mitotic count (>5/HPF), and moderate nuclear pleomorphism.