RT Book, Section A1 Phillips, Raymond E. SR Print(0) ID 1175311610 T1 Valves T2 Venous Insufficiency YR 2021 FD 2021 PB McGraw Hill PP New York, NY SN 9781260461268 LK dermatology.mhmedical.com/content.aspx?aid=1175311610 RD 2024/03/28 AB Attached to the inner walls of the leg veins is a series of delicate valves that have an essential function in the peripheral pump. Paper-thin flaps (or cusps) are paired to form a valve that ensures a one-directional effect on the flow of blood. The free end of each valve flap contacts its mate in the center of the vein. The valves join the vein at the lower part of a bulbous widening. With the flap edges together, the valve is closed.