2. Calcium-2

3. Plasma protein level
Each gram of plasma/serum protein binds 0.84 mg of calcium. Thus a decrease in serum protein level (i.e. hypoproteinemia) will result in a decreased level of bound calcium and will also result in a lowered total serum calcium.

4. Plasma protein level
As the ionized serum calcium remains normal, therefore such a person will not suffer tetany because it is only the ionized calcium which is physiologically active.

5. Renal excretion.
Normally only a small part of calcium lost from the body is excreted in urine.
If excessive amount of calcium are administered, more Na+is being excreted in urine,
Renal loss of calcium is also increased if more Na+ is being excreted e.g. by diuretics.

6. Calcitonin
Produced by the para follicular cells (clear or C cells) of the thyroid gland.
It lowers the plasma Ca++ level, (it antagonizes the action of PTH )
It decreases bone re-sorption and increases the deposition of Ca++ in bones.
It increases urinary loss of Ca ++ by inhibiting the Ca re-absorption in the proximal convoluted tubules.

7. Distribution Most important macro-element of human body
Forms about 1% of adult Body Weight
Important structural element of bones / skeleton and teeth
> 99% calcium occurs in bones as
Calcium Phosphate and calcium carbonate
< 1% in soft tissues

8. Distribution 0.03% of Total Body calcium in blood
Normal Serum/plasma contains 9 – 11 mg/dl
RBCs contain very little Ca++
Ca++ in bone constantly exchanged with that of interstitial fluid
Regulated by PTH, Vit - D3 and calcitonin

9. In plasma Ca++ occurs in two forms
Non diffusible
3.4 – 4.4 mg/dl
Combined with plasma proteins (Albumin)
Not dialyzable
Low in hypoproteinemia

10. In plasma Ca++ occurs in two forms
Diffusible
Ionized
5.45 – 6.23 mg/dl
Physiologically active
 Hyperthyroidism
 Hypothyroidism
If level drops to 4.3 mg/dl Tetany occurs

11. In plasma Ca++ occurs in two forms
Complex
< 0.6 mg/dl
Complex with plasma anions like citrates and phosphates

12. Functions 1. Calcium salts take part in bone and tooth development .
Deficient supply of calcium leads to rickets in children and osteomalacia in adults.
Sufficient calcium intake must be ensured in early life to buildup the skeletal reserves.

13. Functions
If this is not done, then there occurs an increased incidence of osteoporosis in old age because at that time deficiency of sex hormones especially in females results in calcium mobilization from bones leading to osteoporosis

14. 2. Function The clotting of blood needs calcium ions.
Calcium is known as factor iv in blood coagulation cascade.
Prothrombin contains gamma carboxyl glutamate residue which are chelated by calcium during the thrombin formation.

15. 3-Function
By regulating the membrane permeability Ca++ control the excitability of nerves.
If plasma Ca++ level falls markedly, tetany results in which spasms of various muscle groups occur.
Death may occur from convulsions or from laryngospasm.
Excess of plasma Ca++ depresses nervous activity.

16. 4-Function
Calcium ions act as a cofactor or activator of certain enzymes.
A protein namely calmodulin is present within cells which can bind calcium.

17. calmodulin-calcium complex
Becomes attached to certain enzymes which are activated.
Such enzymes include adenylate cyclase. Ca++ ATPase phosphorylase kinase, myosin light chain kinase, phosphodiesterase and phospholipase A 2.
This mechanism also is required for the release of acetylcholine at the neuromuscular junctions.

18. 5-Functions
Calcium ions take part in the contraction of muscle including heart muscle and are involved in the excitation- contraction coupling mechanism.
With an increased plasma calcium, heart stops in systole (calcium rigor)

19. Functions
In addition, a high plasma calcium decreases conduction of cardiac impulses and thus can produce heart block.
Calcium ions potentiate the effects of cardiac glycosides and therefore should not be given to patients who are using these drugs.

20. Functions
Calcium ions are responsible for initiating contraction in vascular and other smooth muscles. Calcium ions enter through specific channels just as is the case with cardiac muscle. Drugs which block these channel (Ca++ channel blockers) have profound effect on the contractility of cardiac and smooth muscles as well as on the conduction of impulses within the heart. These drugs find use in treatment angina pectoris, cardiac arrhythmias and hypertension.

21. Functions
Calcium is essential for maintaining the integrity of capillary wall. in its deficiency, capillary walls become fragile and there is increased permeability of capillaries .In a similar manner it has a role maintaining the integrity of mucosal membranes and cell adhesion.

22. 6-Function
Calcium ions are involved in exocytosis and thus have an important role in stimuls-secretion coupling in most exocrine and endocrine glands e.g the release of catecholamines from the adrenal medulla, and histamine from mast cell is dependent upon Ca++ .

23. 7-Functions
Some hormones exert their influence through Ca++ . For example, the effect of adrenaline on the liver cells to increase glycogenolysis is partly due to an increased Ca++ within these cells which is independent of cAMP.

24. Toxicity of calcium
Excessive intake of calcium can be dangerous because calcium gets deposited in various body tissues resulting in their malfunctioning .This effect of hypercalcemia is seen more frequently if serum Pi level is normal or raised.

25. Calcium excretion
Daily 1240 mg calcium enters the gut, 1000 mg from food and 240 mg from the blood; of this 480 mg is absorbed showing a net absorption of 240 mg.
Feces eliminate 760 mg calcium day which represents the unabsorbed dietary calcium along with calcium coming from the blood.

26. Calcium excretion
Of the 6000 mg calcium filtered by the glomeruli most of it is reabsorbed and the kidneys excrete only 240 mg calcium /day which represents the real excretion of calcium from the body..

27. Calcium excretion
Normally only a negligible amount is lost from the skin but excessive sweating result in an appreciable loss of body calcium.

28. Calcium excretion
Pregnancy and lactation result in a significant loss of mother’s calcium

30. Calcium balance
It is the difference between the quantity of calcium ingested and lost from the body over a certain period of time. If the quantity of calcium lost from the body is less than that ingested, the balance in called positive. If more calcium is lost than ingested, it is called a negative calcium balance.

31. Conditions associated with a positive calcium balance.
Growth
Hyperpituitarism involving growth hormone
Pregnancy
4. Calcium intake after a long period of calcium deprivation

32. Conditions associated with a negative calcium balance.
1. Rickets and osteomalacia
2. Hyperparathyroidism
3. Sprue less absorption
4. Hyperthyroidism
5. Starvation
6. Decreased calcium intake
7. Deficiency of sex hormones in both sexes (e.g. old age)