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calcification, the deposit of calcium salts in tissues and organs that do not normally contain them in undissolved form.
In old persons, lime is deposited in the cartilage of the ribs and larynx. A normal phenomenon is the grains of lime found in the pineal gland and the vascular plexus of the brain (brain sand). Under pathological conditions, calcium salts are deposited both inside and outside the cells. Sometimes these salts take the form of grains or granules, and sometimes they form larger clumps. The process is called petrifaction, and the calcified area is called the petrifact. Calcium salts fall out of solution and are deposited in tissues because of the unstable state of protein colloids, changes in the pH toward greater alkalinity, and increases in calcium concentration in the blood. Several forms of calcinosis are distinguished, according to the mechanism of development.
Dystrophic calcification is a localized process in tissue areas with sharply lowered metabolism, as a result of which oxidative processes are decreased, the tissue becomes more alkaline, and lime falls out of solution. Dystrophic calcification occurs in dystrophic processes (dystrophy) and tissue necrosis.
Calcareous metastases are a manifestation of a general disruption of calcium metabolism in which the calcium concentration in the blood is elevated. Osteomyelitis, myeloma, and other diseases induce processes that destroy bone tissue and release lime from it.
The causes of calcium accumulation in the blood include diseases of the large intestine and kidneys and hypovitaminosis D. In contrast to dystrophic calcification, the sedimentation of lime in healthy, unchanged tissues and organs occurs only in those tissues that normally have an alkaline medium (lungs, stomach, kidneys, and arteries).
Interstitial calcinosis (calcium gout) is distinguished by the fact that there is no depletion of calcium in the bones and no excess concentration of calcium in the blood. The depositing of lime occurs in the skin and subcutaneous tissues or may spread to the muscles and other tissues. The cause of interstitial calcinosis has not yet been clearly shown. It is detected chiefly during X-ray examination. Treatment is both symptomatic and directed toward removing the primary causes of the condition.