There are 3 components of transport system in human beings- blood, blood vessels and the heart.

• The heart pumps oxygenated blood (haemoglobin+4molecules of inhaled oxygen) to all cells of body; the blood then picks up CO₂ released from cell during cellular respiration and becomes deoxygenated again which is sent to lungs for purification/oxygenation.

• Blood is made of cell fragments and plasma. It contains red blood cells, white blood cells, and platelets. It helps in transport of oxygen to cells, exhaling carbon dioxide by picking it from cells and in transport of nutrients and nitrogenous wastes too.

• Blood vessels (veins, arteries or capillaries) are responsible for carrying blood through the tissues and organs.