The primary purpose of venous circulation is to return blood to the heart to be reoxygenated and recirculated. When a person is standing and sitting, the venous half of the circulatory system must work against gravity. In combination with the anatomic feature of the valves, the muscles and tendons surrounding the deep veins act as a pump to force blood out of the leg and past the valves. The venous valves and pumps in the legs offset the effects of gravity and prevent the buildup of hydrostatic pressure (pressure due to weight of fluid) by converting the static puddling of blood into a dynamic venous flow system. Since the circulatory system is a closed circuit, venous return must equal the flow of blood coming into the legs via the arteries. The flow varies with activity, temperature, and position and must be very responsive, since the magnitude of this change can be large. While distribution of blood flow is largely controlled through selective arterial constrictions (narrowing or dilating of arteries to inhibit or promote blood flow to a given part of the body), the venous circulation often functions as a large reservoir where blood can be “stored” while still in the circulation. This generally takes place in the larger veins by a change in the diameter (shape) of the veins and helps to control wild swings in blood pressure that could otherwise occur with a change in position, environment, or emotions.

Venous return is the rate of blood flow toward the heart. Venous return from the legs (peripheral venous return) is achieved by the pumping of the calf muscles with the help of efficient venous valves that prevent backflow of venous blood.