The term ‘transport system’ in human, refers to the circulatory system. After digestion, the digested food like amino acids, glucose, etc., are absorbed in the small intestine. These substances are needed in all living cells in the body such as the brain cells, leg muscle cells, liver cells and kidney cells. The substances are carried from the intestine to other parts of the body by the blood system. In a similar way, the oxygen taken in by the lungs is needed by all the cells and is carried round the body in the blood.