Microcirculation. The third force

Microcirculation, "the third force" in the cardiovascular circuit, has been ignored for many years, while spectacular advances have taken place in cardiovascular surgery. Still, if microcirculation fails, tissue nutrition is impaired and cardiovascular repair becomes futile. Functional Pathology.— Microcirculation is the function of the terminal vascular bed, the vessels having a diameter of 100μ or less. It is by no means a homogeneous apparatus, since it consists of a number of segments which do not react simultaneously or even in the same direction (Fig 1). Teleologically speaking,*the stabilization of capillary pressure is one of its main objects; adequate tissue nutrition is thus maintained. This is accomplished by autcregulation, by which one implies that there isan intrinsic tendency of an organ to maintain constant blood flow, despite changes in arterial perfusion pressure.1It is a mechanism for maintaining nutrient flow when arterial pressure is reduced locally or systematically,