[The physiology of microcirculation]

Since the work of Harvey and Malpighi, there have been more questions than answers in the physiology of the microcirculation. The microvessels and the interstitial connective tissue form a true functional and structural unit in which the capillary is only a passive feature. It is subject to the constraint of the connective tissue that surrounds it, is only a reflection of the hydraulic conditions above and below it and is a luxury metabolic pathway compared with the importance of the derivative or shortcircuit arteriovenous pathway in which the metarteriole is of major importance. Continual renewal, apparent vasomotor character, and extreme permeability sum up the physiology of the microcirculation. The cybernetics is dominated by the arteriolo-venular functioning and by chain rections. Stasis, the opening of arterio-venous anastomoses, and sludge are the main pathological features. Investigation of capillary function remains difficult under clinical conditions, since different methods give a global picture, that of the vascular-tissue unit.