NECROSIS (necrosis; Greek nekros dead; synonym local death) — necrosis, the dying off of a part of fabric or body of a live organism which is followed by the irreversible termination of their life activity.
The N is not only patol, process, it occurs in the course fiziol. regenerations, napr, in epidermis, a mucous membrane went. - kish. path, etc. The irreversible dystrophic changes preceding H., call a necrobiosis, and the necrobiosis proceeding during a long span — patobiozy. The complex of changes of a kernel and cytoplasm of a cell characterizing a condition of a parabiosis is called paranecrosis (see).
Reasons, leading to N., conditionally divide on exogenous and endogenous. The mechanical injury, influence of extreme temperatures, electric current, ionizing radiation, acids, alkalis, salts of heavy metals, microorganisms, etc. are the exogenous reasons. From among the endogenous reasons of N. allocate disturbances of vascular, neurohumoral, allergic and metabolic character.
Distinguish the direct N. caused by direct action of a disturbing factor and the indirect N. arising indirectly through vascular, nervous and endocrine systems.
At the heart of the changes developing in N.'s center fading anabolic and strengthening of catabolic processes lies. At the same time dissociation of breath and phosphorylation, redistribution of ions, a denaturation and coagulation of proteins, disappearance of a glycogen (fig. 1), an inactivation of enzymes and their exit from a cell is observed. Under the influence of hydrolases (see. Autolysis ), and in some cases under the influence of enzymes of microorganisms there is a disintegration of cellular and noncellular structures and the subsequent removal of decomposition products.
The N can arise as cellular pathology and as fabric reaction. In a cell this process can be connected with pathology of a mitosis (mitotic death) or occurs during the period between divisions (interfazny death) as a result funktsional-but-morfol. disturbances of its various systems (see. Cell ). As fabric reaction, includes N. not only death of cells; it is characterized also otgranicheniy (demarcation) and mitigation of consequences of necrosis.
Nekrotizirovanny fabric loses characteristic structure, its cells break up (fig. 2), and their remains are exposed to phagocytosis (see); collagenic and elastic fibers bulk up, are homogenized, collapse. Sites H. become impregnated with blood, there is their infiltration leukocytes and macrophages. In kernels of cells by means of microscopic examination reveal pycnosis (see) with wrinkling and consolidation, condensation of chromatin and a hyperchromia; a karyolysis with characteristic dissolution of chromatin and disappearance of a kernel; a karyorrhexis with education glybok chromatin (fig. 3) and fragmentation of a kernel. Pycnosis, a karyolysis and a karyorrhexis can be shown as independent forms of change of a kernel, and also as consecutive stages of process of N. V to cytoplasm of cells at N. observe coagulation, homogenization, vacuolation and dissolution, disintegration with formation of a detritis. Degree and the nature of changes in a kernel and cytoplasm at N. can not match.
In development of N. distinguish three stages: a prenecrosis (a condition of body, fabric, a cell before emergence of irreversible changes), death (the irreversible termination of life activity) and destructive changes (disintegration, removal, an otgranicheniye of the remains).
Classifications N are constructed taking into account a stage of process, features of its emergence (primary, secondary), prevalence (focal, total), a wedge, pictures, etc. Depending on the reason which caused N. and conditions of its development, and also from funktsional-but-morfol. features of bodies and fabrics, in to-rykh N. develops, allocate its following kliniko-anatomic forms: coagulative (dry), kollikvatsionny (wet), gangrene (see), heart attack (see).
Coagulative N. is characterized by processes of a denaturation of proteins with formation of almost insoluble connections that leads to consolidation of nekrotizirovanny fabric. More often it arises in the fabrics rich with protein and poor in liquid, napr, in kidneys and a spleen, at wax-like or so-called tsenkerovsky N. of muscles, caseous N. at tuberculosis, fibrinoid N. at allergic diseases, etc.
Kollikvatsionny N. is characterized by fusion of dead fabric quite often with formation of cysts; it develops in the fabrics rather poor in protein and rich with liquid, in to-rykh there are favorable conditions for hydrolytic processes. Typical kollikvatsionny N. in the form of the center of a softening meets in a head and spinal cord at atherosclerosis. In some cases it can be secondary as the result of fusion of mass of coagulative N.
V the fabrics adjoining to the environment can develop gangrene. At the same time as a result of transformation of blood pigments and formation of ferrous sulfide devitalized sites become gray-brown or black. A kind of gangrene are decubituses (see) — become lifeless, exposed to pressure, superficial body parts, napr, skin and soft tissues in the field of a sacrum or a big spit of a femur.
The heart attack represents N.'s center of body (fig. 4) resulting from sudden disturbance of local blood circulation.
In favorable conditions (the limited center of N., sufficient blood supply, cellular type of regeneration, etc.) the died fabric is replaced initial, i.e. there occurs its complete recovery. More often on site than necrotic masses as a result of their organization fibrous fabric expands and the hem is formed. In some cases there occurs fluidifying of mass of N. or adjournment of salts of calcium in them — petrification. At an incomplete rassasyvaniye of necrotic masses they are delimited by connecting fabric and there occurs their encapsulation. Nekrotizirovanny fabric can separate and be in an organism in the form of the sequester or be torn away as a result of mutilation.
The remote effects of N. are more often presented by depression of function of the struck fabric or body. The beam N. resulting from impact of ionizing radiation can lead to development of a tumor further.
Value H. for an organism is defined funkts, a role of the dying-off part, localization, the sizes of the center of N., etc. As a result of N. hypofunction of the struck body, etc. can be observed; death of an organism is possible.
Bibliography: Avtsyn A. P. and Shakhlamov V. A. Ultrastructural bases of pathology of a cell, page 35, etc., M., 1979; Davydovsky I. V. General pathology of the person, M., 1969; Koltover A. N., etc. Pathological anatomy of disturbances of cerebral circulation, page 17, M., 1975; Lopukhin Yu. M., Kogan E. M. and Karaganov Ya. JI. Ultrastructural bases of viability of a liver, kidneys, hearts, Atlas, page 18, M., 1977; P about-likara. and B of e with with and M. Elements of pathology of a cell, the lane with fr., M., 1970; Sarkisov D. S. and In t yu r and B. V N. Submicroscopy of destructive and regenerator intracellular processes, M., 1967; Serov V. V. and Spiders V. S. Ultrastructural pathology, page 157, M., 1975; Strukov A. I. and Serov V. V. Pathological anatomy, page 51, etc., M., 1979.
E. F. Lushnikov.