Degeneration (a870)

DEGENERATION (from Latin degeneratio - regeneration, degeneracy), a term having dual meanings in pathology: in a broader sense, it denotes such a pathological deviation from the normal type of organization (in humans, animals, plants) that occurs under the influence of hereditary predisposition and, deepening from generation to generation, gradually leads to the extinction of a given species; such degeneration is also denoted by the word degeneracy (see). Specifically, in cellular pathology, degeneration is understood as a change in cells (resp. their individual parts, e.g., nuclei) or intercellular substance, arising mainly due to external harmful influences during the individual life of an organism. Corresponding to the diversity of these harmful influences (infectious and toxic effects, various physical and chemical agents, injuries), changes of this kind can be extremely different in both nature and extent, with what is common to all of them being: from a morphological side - the appearance in cells (resp. intercellular substance) of substances quantitatively or qualitatively foreign to this location, and sometimes even the complete transformation of this tissue part into such a substance, while from a physiological side - weakening (and sometimes complete destruction) of the normal vital properties and functional abilities of the corresponding elements. The physical and chemical structure of the tissue also undergoes more or less significant deviation from the normal type. Since all such processes, upon reaching a certain intensity, can lead to the death of the affected tissue part, they are often designated as "necrobiotic," i.e., life processes leading to death (the corresponding word of Russian root - regeneration). According to modern views, the basis of degenerations lies in various metabolic disorders, arising either locally or throughout the entire organism. The essence of the changes occurring in tissues during this is known so far only in the most general terms, and it should be noted that very often the matter is not even about degeneration in the proper sense of the word, i.e., not about the destruction of protoplasm or its transformation into some other substance, but only about the appearance in it of certain particles absorbed by the cell from the outside (from the plasma washing it), but not assimilated (so-called pathological infiltration). More precisely, here there may be: 1) excessive accumulation in cells of any normal component part, 2) disruption of the solubility conditions of a particular substance, leading to its precipitation, 3) change in the dispersity of various colloids (transition of sol to gel), 4) appearance of substances, although occurring in the body, but foreign to this location, and their appearance may be due either to the loss by the tissue of the ability to assimilate this substance or to the chemical breakdown of the tissue, and finally 5) appearance in the tissue of substances completely foreign to the normal organism, which may either form as a result of improper metabolism or be brought into the body from the outside. Microscopic research in all these cases establishes the presence in the tissue of certain products, foreign in composition or quantity to the normal structure of this location, while determining the chemical nature of these products (proteins, carbohydrates, fats, salts) makes it possible in most cases to determine what type of metabolic disorder is present. The classification and nomenclature of degenerations, in their main features, are entirely determined by the forms of metabolic disorders that underlie them. Thus, one speaks of protein, fat, carbohydrate degeneration and of deposits appearing under the influence of disorders in salt metabolism; to degenerations are also attributed violations of pigmentation. - The term degeneration acquires a somewhat special (although in essence not different from the described) meaning in nervous pathology. In relation to nerve fibers, this name is usually associated with the concept of gradual breakdown of the nerve fiber, occurring as a result of the death of the corresponding nerve cell or due to disruption of the connection of the fiber with the latter (see Wallerian degeneration), more rarely - due to direct toxic effects on the nerve (see Neuritis). In nerve cells, degeneration can sometimes express itself only in a change in thetigroid substance or neurofibrillar apparatus without the appearance in the cell of visible fat particles, glycogen and other inclusions foreign to it, m. skvortsov.