Necrosis - mortification limited parts of a living organism, a separate body or its parts, tissues or cells.
Causes necrosis different: 1) termination of the arterial blood supply due to blockage of the artery by a blood clot, embolus, narrowing and zapustevanie artery, for example when arteriosclerosis; 2) the action of heat (burns) or cold (frostbite); 3) the action of strong poisons (such as mercuric chloride on the kidneys, intestines mucous membrane), acids, alkalis; 4) the action of bacterial toxins;
5), the sustained pressure on tissues (for example, the formation of bedsores in the sacrum and coccyx in debilitated malnourished patients, bedsores trachea and larynx from the pressure tracheotomies tube).
There are necrosis dry, or coagulation, and necrosis wet, or colliquation. When dry, the dead tissue necrosis dry, wet they are in the process of dissolving. A kind of dry necrosis is cheesy (cheesy) necrosis, in which dead weight have views of the dried cottage cheese or dry putty.
Development of necrosis precede changes in metabolism and structure of the smallest parts of the cytoplasm of cells that can be detected by histochemistry and electron microscopy. These changes (see Degeneration of cells and tissues) to a certain limit reversible, but with great strength or duration of the disease-causing effects become irreversible and become necrotic.
Microscopic examination of the characteristic signs of necrosis are changes in the kernel - dissolving it (karyolysis) or the collapse of glybki (kariorexis).
A variant of necrosis is gangrene (see).
Around the site necrosis develops reactive demarcation inflammation, demarcates the dead tissue from a living. Inflammation promotes the resorption of dead tissue with subsequent replacement of dead section scar (see Regeneration).
Thanks demarcation inflammation of the dead tissue may be rejected from the living (sequestration) or encapsulated (ogranichivatsya fibrous capsule).
In dead weight are often delayed lime (see Calcification).