While explaining the effect of cold water on blood in restoring its impaired circulation, a brief idea of the circulation system of blood was given earlier. Here, we now give the major function of the blood. The blood carries food to the cells in its circulation.
In other words, blood is the transporter of food from the heart to the cells/tissues of the body. Let us study how blood performs this function, by firstly knowing about its constituents. The constituents of blood are:
1. RED BLOOD CELLS (RBC): Their main constituent is the pigment, called HAEMOGLOBIN, which is a protein with iron in its molecules. Haemoglobin transports oxygen and carbon-dioxide.
2. WHITE BLOOD CELLS (WBC): These provide immunity to the body. The WBC consume bacteria viruses and debris that get entered into the body and thus form special proteins, called the ANTIBODIES that protect against infection.
3. BLOOD PLATELETS (or THROMBOCYTES): They are small spherical bodies of blood. Their important role is in the formation of solid plug, that is, a CLOT at the site of injury to a blood vessel, so as to prevent further loss of blood.
4. PLASMA: This is the liquid part of blood into which float different types of blood cells, i.e., RBC, WBC and platelets. It consists of several salts, glucose, amino acids, proteins, hormones and also digested as well as excretory product of food. ‘SERUM’ is also blood plasma from which is removed the blood-clotting protein.
In the foregoing articles we have described the constituents and qualities of blood. We now give an account of the main functions of blood in the body.