Tissue fluid, also known as tissue interstitial fluid, is a liquid medium that maintains many kinds of physiological equilibrium, and delivers nutrition and (metabolite molecular what? Molecular is an adjective) between cells and capillary vessels.Thus far, we have referred to capillary blood as finger blood, the blood tested by a portable glucose meter. Venous blood is that which is taken in regular blood sampling in hospitals. The samples of capillary and venous blood are known as whole blood, and the components of tissue fluid are primarily the same as plasma in whole blood.