ABSTRACT
Many previous studies of blood/tissue/lymphatic transport have used isolated organs or whole animals under general anesthesia. Under these conditions, the transport of fluid and metabolites is articially low in comparison to animals that are actively moving. The transport of fluid and metabolites from the blood to the tissue is critically important for maintaining the viability and function of cells within tissues. In the tissue, the fluid transported out of the capillaries is passively carried in the interstitial space via a percolation process around interstitial matrix proteins. The low rate of transcapillary ltration and lymph formation in many tissues is explained by standing plasma protein gradients within the intercellular cle of continuous capillaries and around fenestrations. Periodic tissue motions are signicantly more effective to enhance the lymph ow than elevation of the venous pressure, which is also associated with enhanced fluid filtration.
