Serum calcium

Calcium is the most abundant cation in the body. The atomic formula is Ca and the atomic weight is 40.08. Normal adults contain 25 to 30 mol of calcium, more than 99% of which are present in bones and teeth. Bone is the largest calcium storage in the body. Extracellular fluid contains only about 27 mmol of calcium. Although the content is small, it maintains normal neuromuscular stress. Glandular secretion and the activity of some enzyme systems play an important role especially in the process of hemagglutination. The intracellular fluid contains almost no calcium. Most of the calcium in the blood exists in the plasma, and the plasma calcium has two parts, non-diffusive calcium and diffusible calcium. Non-diffusive calcium is bound to protein (approximately 1 g of protein binds 0.87 mg of calcium), which accounts for about 40% to 50% of total calcium in the plasma. The diffusive calcium is mainly ionic calcium (Ca2 +), and a small part of calcium salts (such as Calcium citrate, calcium salts of other organic acids, calcium bicarbonate, etc.). The relationship between non-diffusive calcium and diffusive calcium is affected by the concentration of H + and HCO3-, which maintains a balance under physiological conditions, which can be expressed by the following formula.