Tetany-

Titany is disease that occurs due to decreased ionized fraction of serum calcium which may be due to-
a) An increase in the PH of blood
b) Poor absorption of calcium from the intestine
c) Decreased dietary intake of calcium
d) Increased renal excretion of calcium as in nephritis
e) Increased retention of phosphorous as in renal tubular disease

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.

Factors which influence blood calcium level-

The entire blood calcium is confined to plasma since erythrocyte membrane is impermeable to calcium ions. The plasma calcium whose total content is 9-11mg/100 ml, in three different forms.
a) Ionized-which is diffusible through membrane and capillary wall
b) Non ionized protein bound-which is combined with plasma proteins and not pass through the capillary wall
c) Non-ionized-complexed-which forms complex with citrates,bicarbonates and phosphate ions, but still is capable of passing through the capillary wall.