Incrustation

INCRUSTATION (from Latin incrustare—to cover with a crust or layer of something), impregnation (from Latin impregnare—to fill, to stuff with something). Both words are used in the same sense to denote the adsorption by some material in the organism of one substance or another from surrounding juices or contacting fluid. Although the word "incrustation" should be understood as adsorption in the strict sense, i.e., the concentration of a substance on the surface of a material (formation of a crust), and the word "impregnation" as absorption, i.e., the saturation of a material with a substance—in pathology, both words are used without regard for this difference, given the impossibility in individual cases of establishing the aforementioned distinction. The material that undergoes incrustation is most often some dead substrate, either in the form of large foci of tissue necrosis, accumulations of inflammatory exudate, or thrombi, or in the form of individual dead cells or tissue fibers; less often, incrustation concerns tissue elements that have not undergone necrosis and have not had their vital activity disturbed at all; finally, parasites and foreign bodies that have entered the organism can undergo incrustation. The substance that incrusts or impregnates the listed materials is most often one salt or another, which precipitates from a solution and, as it were, saturates the material. This includes: incrustation of dead mass with lime salts in infarcts, thrombi, and tuberculous foci; incrustation of individual dead cells, for example, of the brain, myocardium, elastic membrane of arteries, and collagen fibers in scars and tumors; incrustation of dead parasites; and incrustation of accumulations of inflammatory exudate, dead tumor masses, and foreign bodies (a catheter fragment) in the urinary tract with salts precipitating from urine. Furthermore, in foci of hemorrhages, one observes the incrustation of collagen and elastic fibers with iron (usually phosphate), which is a product of hemoglobin decomposition. Sometimes, a simultaneous incrustation of material with two substances occurs, for example, the incrustation of dead cells of the nervous system with lime and iron; sometimes one can see a sequence in such impregnation with two substances; for example, the internal elastic membrane of an artery in corresponding cases is often first impregnated with iron and then with lime salts. The mechanism of incrustation processes is the same as that of adsorption in general; in particular, in incrustation with lime salts, the onset of alkalosis of the medium plays a large role. The significance of incrustation for the organism is not always the same: sometimes one can speak of its positive significance, for example, when incrustation with lime salts immobilizes dead material or blocks a tuberculous focus; in other cases, however, incrustation has a negative significance, since it deprives one tissue or another, for example, a vessel wall, of its elasticity and softness, making it brittle. Sometimes, individual tissue fibers that have undergone incrustation acquire the significance of foreign bodies; giant cells and the proliferation of connective tissue appear around them. A prototype of incrustation that occurs during the normal development of tissues is the impregnation of osteoid tissue and the ground substance of hyaline cartilage with lime at the border of ossification during bone development. The term "impregnation" is also used in histological technique in relation to the staining of tissue elements [for example: impregnation (see) with silver, GOLD].

A. Abrikosov.