Comparison of viscoelastic properties of walls and functional characteristics of valves in lymphatic and venous vessels.

The principal function of the lymphatic and venous system is to maintain a favorable environment for cells of the body. As a consequence mainly of hydrostatic forces, shifts of fluid usually occur between the vascular system and the extracellular space. To compensate for these shifts the veins are capable of active and passive changes in capacity that serve to modulate the filling pressure of the heart by adjusting the central blood volume. In addition to the venous function, the lymphatic function also contributes to compensate for the fluid shifts by drainage from the interstitial space. Namely, the general function of the lymphatic system is to return fluid and protein which escapes from the blood capillaries to the lymph circulation. To elucidate the mode of venous and lymph transport, therefore, it is of essential importance to obtain basic knowledge of the mechanical characteristics of the walls of the vessels and the functional characteristics of the lymphatic and venous valves dividing two adjacent compartments. In this communication, in order to answer the question, "Are Lymphatics Different From Blood Vessels?", I would like to review a comparison of viscoelastic properties of walls and functional characteristics of valves in lymph and venous vessels by use of our original data obtained with isolated canine veins and thoracic ducts and with isolated bovine mesenteric lymphatics (1-9).