Venous return from the lower limb: muscle pumps, normal and disordered function

The veins are the ‘capacitance vessels’ of the circulation and contain about two-thirds of the total circulating blood volume. Local changes in blood volume are controlled by changes in venous tone mediated by the sympathetic system. The most important function of the superficial veins of the lower limb, as elsewhere in the body, is thermoregulation.Venoconstriction is effected by adrenergic sympathetic nerve endings, and sympathetic stimulation by emotion or pain, or during exercise, also results in superficial vasoconstriction. The deep veins have less powerful muscle coats and mainly act as passive blood conduits.