Factors influencing plasma level of Calcium-

1) Parathroid hormone- It increase calcium absorption from ileum in the presence of vitamin D.
2) Vitamin D- It enhances absorption of calcium from the intestine and thus maintains the normal plasma calcium concentration
3) Plasma proteins- As mentioned above nearly half of the blood calcium is bound to plasma protein will be accompanied by the decrease in the total calcium level.
4) Plasma phosphate- Calcium and phosphate ions in plasma have a reciprocal relationship.
5) Calcitonin- An increase in the ionized calcium level in the plasma is the stimulus for the production of calcitonin which then causes a deposition of calcium in bones.

Biochemical role of calcium-

Calcium is the principle mineral and is an essential constituent of the cell and has following function in the body-
1) Calcium along with phosphorous is essential for the formation of the developments of bones and teeths.
2) Ionized calcium is required in blood coagulation process
3) It regulates the excitability of nerve fibers and nerve centers.
4) It is essential for nerve impulse and muscular contraction and regulates the permeability of membrances.
5) It is required for maintaing the integrity of intracellular material.
6) It is required for activation of several enzymes such as succinate dehydrogenase, ATPase and certain proteolytic enzymes.

Principal Element-

These includes calcium, magnesium, sodium, potassium, phosphorous, sulphur and chlorine.
Out of these, Na, K and Cl2 are involved mainly in the maintainance of acid base balance and osmotic control of water metabolism; Ca, P, Mg are the constituents of bones and teeth; phosphorous is a constituent of body cells of soft tissue, such as muscles, liver etc. sulphur in cysteine and methionine, thiamine, biotin and CoA.

Vitamin D-

Deficiency of vitamin D results into “ Rickets” which is characterized by lack of calcification of hypertrophic cartilage zone and thus the bones are affected. Vitamin D plays an important role in the absorption of calcium and phosphorus from intestinal tract. In ricketier persons the phosphate blood serum level is high which is brought down to a normal value by this vitamin. Vitamin D is used in rickets and for the management of hypocalcemia. In fully grown bones in adults there is a tyupe of deective mineralization of ostoid tissue termed as Osteomalacia