| Abstract: | The main physiological function of the capillary blood vessels consists in sustaining the exchange processes between blood and tissues. The transport of water and substances dissolved in it occurs by filtration through the capillary walls. The filtered liquid flows through the tissues (cells and other structures) in the zone of influence of the capillary (“tissue cylinder”) and later almost all of it returns into the capillary; only a small part of the liquid drains into the lymphatic capillaries. Insufficiency of such drainage leads to edema, i.e., filling of water into the tissues. The walls of the capillaries are almost opaque for large albuminous molecules. Therefore the motion of the liquid through the walls is determined not only by the pressure drop, but also by osmosis effects. In the tissue the motion of the liquid is similar to filtration through a porous medium and in some cases it is accompanied by reverse attachment of water, its absorption by tissues, and other phase reversal-type phenomena. The theoretical investigation of transcapillary transport of liquid is of interest for solving a number of physiological problems, in particular, for understanding the mechanisms of regulating exchanges in the tissues. Below, a quasi-one-dimensional model is proposed which describes the hydrodynamics of transcapillary filtration. The basic equations are formulated in Sec. 1 and the subsequent sections contain a discussion of the model including its comparison with the results of other authors (Sec. 3). |
