calcium

Definition calcium

calcium: calcium n. a metallic element essential for the normal development and functioning of the body. Calcium is an important constituent of bones and teeth: the matrix of *bone, consisting principally of calcium phosphate, accounts for about 99% of the body's calcium. It is present in the blood at a concentration of about 10 mg/100 ml, being maintained at this level by hormones (see thyrocalcitonin, parathyroid hormone). It is essential for many matabolic processes, including nerve function, muscle constraction, and blood clotting.

The normal dietary requirement of calcium is about 1g perday: dairy products (milk and cheese) are the principal souces. Its uptake by the body is facilitated by *vitamin D; a deficiency of this vitamin may therefore result in such conditions as *rickets, *osteoporosis, and *osteomalacia. a deficiency of calciumin the blood may lead to *tetany. Excess calcium may be deposited in the bofy ad *calculi (stones), especiallly in the gall bladder and kidney. Symbol: Ca.