PARATHYROID GLAND PHYSIOLOGY. 99% calcium of our body is in the crystalline form in the skeleton and teeth Of the remaining 1% 0.9% intracellular less than 0.1% in the ECF. The extracellular fluid calcium concentration is about 9.4 mg/dl.
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less than 0.1% in the ECF
Even minor variations in concentration of free ECF calcium have profound and immediate impact on the sensitivity of excitable tissues
The entry of calcium into secretory cells which results from increased permeability to calcium in response to appropriate stimulation triggers the release of secretory product by exocytosis
In pancreatic beta cells calcium entry from the ECF in response to membrane depolarization leads to Insulin secretion
(rickets, pregnancy, lactation)
(excess calcium and vitamin D in diet, diseases causing bone resorption)
(4) postmenopausal lack of estrogen secretion because estrogens decrease the number and activity of osteoclasts
(5) old age in which growth hormone and other growth factors diminish greatly plus the fact that many of the protein anabolic functions also deteriorate with age
(6) Cushing's syndrome estrogens decrease the number and activity of osteoclasts, massive quantities of glucocorticoids secreted in this disease cause decreased deposition of protein throughout the body and increased catabolism of protein and have depressive effect on osteoblasticactivity