Capillaries are very thin walled, small vessels which form a network in the tissues for the absorption of nutrients and exchange of respiratory gases between the tissue and blood. They form a bridge between an artery and a vein.

The heart is the major pumping organ of the human circulatory system, that pumps blood to all body organs. The arteries carry oxygenated blood away from the heart and the veins carry deoxygenated blood to the heart.