[Reaction of the wall of veins of the extremities to a disturbance of venous outflow].

By means of light and electron microscopy the dynamics of certain morphological changes occurring in veins of the rabbit and rat pelvic extremities have been studied at various time intervals of venous congestion produces by ligation of the posterior vena cava. At early postoperative stages, certain lesions of the venous endothelium appear, which are manifested as an increased permiability of the endothelial cells, thickening of the borders (silver impregnated) between endotheliocytes, interaction with blood cells, exfoliation from the basal membrane and an increased pinocytic activity. Later on, focal thickenings of the internal intima appear, at first, at the expense of blood leukocyte migration into the subendothelial layer, then atypical smooth muscle cells and fibroblasts appear there. In 1-2 months intimosclerosis develops. An increased proliferation of all cellular types in the venous wall takes place. In a number of the animals a stable hypoxia of the venous wall is revealed which evidently results in certain endothelial lesions. That plays the main role in appearance of other changes in the venous wall structure which terminate in phlebosclerosis.