Calcium is the element with the symbol Ca and atomic number 20. It has atomic mass of 40.078 amu.
This mineral is the most abundant electrolyte in the human body, and in healthy adults, accounts for about 2% or 1,300 g, of body weight.
The skeleton is an important reservoir of calcium, serving both a maintain plasma calcium concentrations and to make optimal use of ingested calcium.
Approximately 99% of total body calcium is stored in skeleton and teeth, with many functions and serves also as a structural element in bone.
The rest of the calcium in the body has other important uses, such ‘neurotransmitter release’, muscle contraction and ‘exocystosis’ (a durable process by which a cell directs the contents of secretory vesicles out of the cell membrane).
In the plasma there is also a protein bound calcium fraction, which is present at concentration of 3.2 mg/100 ml (0.8 mmol/l).
About 50% calcium in plasma is ionized and 10% is complexed with citrate phosphate, bicarbonate and lactase.
From birth to approximately 20 years of age, when skeleton reaches its full size and density, calcium content increases by some 40 fold.
Numerous end organs participate in the regulation of calcium. The gastrointestinal tract and kidney, along with bone, are major regulators of calcium balance.
Calcium receptors in the liver may monitor the calcium concentration in plasma, sending signals to the brain and affecting other peripheral sites in the body.
Distribution of calcium in human body
