[Histochemical aspects of the aging of connective tissue]

The senile involution of the peri-vascular connective tissue is followed by structural and functional modifications of the small vessels, especially pre-capillary arterioles and venules of the efferent system. Each modification, including the physico-chemical modification of the basal membrane of the connective tissue ("peri-microvascular sheath of proteoglycans" according to Merlen) causes a reaction response of the capillary endothelium with thickening of the basal membrane, as seen in skin biopsies of the leg after elastic bandage contention of long duration. The smallest arteries, the "padded" arterioli and the microvenules of the valves, the arteriovenous anastomoses, the smallest veins and the interstitial lymphatic channels form with the basal substance of the connective tissue to which they are incorporated, a true "functional" unit (Curri and Tischendorf, 1954).