Blood is a thick fluid containing corpuscles: cells of two types-red and white. The red corpuscles in the blood are so numerous that they give red colour to the blood. Their function is to carry oxygen from lungs to tissues. The white corpuscles, which are much fewer in number, are colourless and irregular in shape. They act like the guard of the body. All sorts of germs entering the blood are killed by them.
Thus body having large percentage of these corpuscles becomes proportionately healthier. The main functions of blood are: (i) to supply oxygen to various organs of the body; (ii) to remove waste products of the body: (iii) to supply food to various organs of the body: and (iv) to manufacture digestive juice.
Coagulation of Blood: When blood is withdrawn from the body and allowed to be still for some time, it becomes semisolid, i.e., it coagulates- After a while, the clot begins to shrink and becomes a pale yellow fluid” called serum.
The coagulation of blood is due to change of soluble substance called fibrinogen.
Clotting of blood at the wound site has its advantages for it plugs the in the blood vessels and prevents further bleeding.