The system that transports nutrients and collects waste materials for disposal in the human body is called the circulatory system. The circulatory system consists of the central organ i.e., the heart, blood vessels and circulating fluid called blood. However, blood never comes in contact with the tissues or the spaces between them, so there exists a parallel system or the lymph system that collects waste material from the interstitial fluid of the tissues and is also capable of defending the cells from pathogens.