PLASMA.

Plasma is primarily water in which proteins, salts, nutrients and wastes are dissolved. It has been estimated that in a normal person plasma constitutes about 55% by volume of the blood. Constituents. Water constitutes about 90% of plasma, 10% are dissolved substances.

Most of the dissolved substances are maintained at a constant or nearly constant level, but others occur in varying concentrations. The substances dissolved or present in plasma vary in their concentrations, with the condition of the organism and with the portion of the system under examination.

Categories of solutes.

The solutes can be divided into six categories:

1. Inorganic salts (ions)

2- Plasma proteins

3- Organic nutrients

4. Nitrogenous waste products

5- Special products being transported

6-gases which are dissolved.

1. Inorganic ions or mineral ions. %age. Together the inorganic ions and salts make up 0.9 per cent of the plasma, of humans, by weight; NaCl. More than two thirds of this amount is sodium chloride the ordinary table salt. Even if the total concentration of dissolved substances remains the same, shifts in the concentration of particular ion can create serious disturbances. pH of blood. The normal pH of human blood is 7.4; and it is maintained between narrow limits, because the change in pH would affect the chemical reactions of the body.

2. Plasma proteins. %age. These constitute 7-9 percent by weight of the plasma. Synthesis. Most of these proteins are synthesized in the liver. Antibodies. Some of the globulins, called immunoglobulins or antibodies, are produced in response to antigens, by lymphocytes; and then are passed to plasma, and lymph. Immunoglobulins play important role in body‟s defenses against disease Clotting proteins. The proteins like prothrombin acts as a catalyst in blood clotting process. Fibrinogen takes part in the blood clotting process.

3. Organic nutrients. Nutrients in the blood include glucose, fats, phospholipids, amino acids and lactic acids. Source. Some of them enter the blood from the intestine (absorption). Lactic acid is produced in muscles as a result of glycolysis, and is transported by blood to liver. Cholesterol is an important constituent; it is metabolized to some extent, but also serves as precursor of steroid hormones.

4. Nitrogenous waste Plasma also contains nitrogenous waste products formed as a result of cellular metabolism. These products are carried from the liver where they are produced, to the organs from where they are removed i.e. kidneys. Urea and small amounts of uric acid are present in plasma.

5. Hormones. All the hormones in the body are carried by blood – so they are present in the plasma.

6. Gases. The gases such as CO2 , O2 are present in the plasma of the blood.