Blood is a viscous fluid of bright red color, heavier than water and slightly alkaline. It consists of two components. The liquid part is called plasma, and the large number of cells is called blood corpuscles suspended in the plasma.

(a) Plasma : It is a straw-colored fluid consisting of the following chemicalonents:

(1) 90% of water.

(2) 7% of plasma proteins like serum albumin, serum globulin and fibrinogen.

(3) 3% of remaining substances, such as

(i) Nutrients like glucose, amino acids and fatty acids.

(ii) Inorganic salts like bicarbonates of sodium, potassium, calcium and magnesium.

(iii) Organic compounds like enzymes, hormones, antibodies, antitoxins and heparin, etc.

( iv) Gases like oxygen, carbon dioxide and nitrogen.

(v) Waste materials like urea, uric acid, etc.

The composition of plasma is altered in tissues and controlled by organs like the liver and the kidneys.