The importance of blood is proved by its manifold functions:

1. Prevention of desiccation: Blood supplies an adequate quantity of water to cells and prevents the tissue from dehydration. However dry the skin may be blood always keeps the interior of the body supplied with water.

2. Distribution of food: Blood distributes back digested and absorbed food from the alimentary canal to all parts of the body.

3. Transportation of respiratory gases: Blood carries oxygen from the lungs to the different tissues in the body and carbon dioxide from the body tissues back to the lungs.

4. Transmission of hormones: Blood conveys hormones, the secretion of ductless glands, from the glands to the tissues and organs whose metabolism and functions they control.

5. Removal of waste products: Blood washes out waste materials like urea and uric acid from the cells and carry them to the organs of excretion.

6. Equalization of temperature: Blood maintains the body temperature within the body by carrying heat from active tissues to extremities (skin, lungs) where it can be dissapated.

7. Defense against parasitic invasion: With the help of white blood corpuscles, blood destroys germ cells and protects our body from diseases.

8. Chemical deliberation: Blood brings about many chemical transformations, the chief being the formation of antibodies which often confines a further attack of a particular disease.

9. Clotting and healing the wounds: Bloods stops excessive wastage of nutrients from cuts and wounds by forming a clot. The leucocytes often help in healing the wounds. It is believed that a few of them are converted into connective tissue elements of the repaired region.

Because components of blood change in response to changes in the body (diseases, infection, malfunction), blood chemistry is useful for clinical diagnosis.