Within each organ: Networks of capillaries function to bring blood close to cells. All cells are surrounded by a highly branching,interweaving network of capillary vessels This network provides every cell in the body with short-range access to the blood supply.Thus it is possible for metabolites move from blood to interstitial fluid,and from interstitial fluid to cells,by diffusion.. In order to support cellular metabolism within organs,cells need to exchange gases,fuel,and waste products.O2 and fuel have to be delivered,and CO2 and other waste products need to be removed from cells.This is accomplished by Cast of capillary network diffusion between cells and the interstitial fluid that surrounds them