Calcium metabolism disturbances
Most part of calcium is located in the bones (bones are calcium depot) where it is binded to the organic substance of the bone tissue. It is stable in the compact bone substance and labial in the spongy substance of epiphyses and metaphyses. Calcium metabolism is regulated by nervous and humoral systems. The most important for this are Parathormone of parathyroid gland and Calcitonine of thyroid gland. Parathormone stimulates washing out calcium from the bone. Calcitonine vice verse contributes to the transition of calcium from the blood to the bone.
In parathyroid hypofunction and thyroid hyper-function, blood calcium amount decreases, in parathy-
roid hyperfunction and thyroid hypofunction, calcium is washed out from the bones. This may be of two types: lacunar and sinusal. Lacunar one takes place with the help of osteoclasts when large cavities in the bone tissue are formed. In sinusal resorption, the bones are dissolved without the participation of the cells, in this case so-called «liquid bone» when small-cell structures are formed. Such complications as spontaneous (unexpected) bone fractures can be observed.
Disturbances of calcium metabolism are called calcinosis, calcium degeneration, or calcification.
According to the location calcinosis may be intracellular, extracellular and of both locations.
According to propagation calcinosis are divided into systemic and local.
According to the mechanism of its development, calcinosis may be metastatic, degenerative, metabolic.
Staining with H&E demonstrates calcium salts as deeply basophilic, irregular and granular clumps. For identification of calcium salts we usually use special reaction called silver impregnation method or Kossa's method. Calcium deposits are stained black.
Metastatic calcinosis (calcium metastases) is of systemic character. Its main cause is hypercalcemia, which may be of endocrine origin in hyperproduction of Parathormone or hypoproduction of Calcitonine. It may be associated with the reduction of calcium excretion from the organism. That is why calcium
metastases develop in multiple fractures of the bones, multiple myeloma, osteomalacia (when the bone becomes soft), lesions of the large intestine (the place of Ca excretion), vitamin D abundance. Calcium salts precipitate in different organs, more frequently in the lungs, gastric mucosa, kidneys, myocardium, arterial walls. Sedimentation in the lungs and stomach is due to acid products, in myocardium and arteries because they are washed with poor with carbon dioxide arterial blood.
In degenerative calcification, or petrifaction, calcium salts are deposited in the tissues with marked degeneration changes or in necrotic zones: caseous foci in tuberculosis (necrosis looks like cottage cheese-curds), in syphilitic gummas, infarction places, tumors, foci of chronic inflammation as well in the scars, cartilages, dead parasites (echinococci), dead fetus (lythopedion).
Metabolic calcification (calcium gout) develops in instability of buffer systems (pH and protein colloid) when calcium is not retained in the blood and tissue fluid even at its low concentration as well as in calcergia, i.e. increased sensitivity of the tissues to calcium. Metabolic calcinosis may be systemic and local. In interstitial systemic calcinosis, calcium is accumulated in the skin, subcutaneous fat, along the sinews, fasciae, aponeuroses, in the muscles, nerves, vessels, in local calcinosis in the skin of the fingers and toes in the form of plates.
The outcome is unfavorable, calcium does not resolve.
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