Blood as a Transport System

Abstract

Blood travels to all parts of the body, and the flow rate in most parts of the circulation is rapid. It therefore provides an efficient transport system for many essential nutrients, waste substances and effector molecules (e.g. hormones). By providing a link between separate tissues, blood enables the biochemical activities of one organ to influence the activities of another. Nutrients absorbed from the gastrointestinal tract are transported by the blood to the tissues, metabolites are moved between organs and waste substances are transported for excretion; hormones produced by one organ are carried in the blood plasma to their target tissues. In this way the transport functions of blood play an essential role in the overall homeostatic mechanisms of the body by co-ordinating the biochemical activities of its different parts. In addition, several blood components bind and transport foreign substances (e.g. drugs, antibiotics) introduced into the body and can markedly influence their pharmacological or toxicological effects.