WASHINGTON, DC - JANUARY 20: U.S. President Donald Trump delivers his inaugural address on the West Front of the U.S. Capitol on January 20, 2017 in Washington, DC. In today's inauguration ceremony Donald J. Trump becomes the 45th president of the United States.
One-Way Valves in the Veins. One-way valves consist of two flaps (cusps or leaflets) with edges that meet. These valves help veins return blood to the heart. As blood moves toward the heart, it pushes the cusps open like a pair of one-way swinging doors (shown on the left).
There are valves in veins to prevent backflow. The blood pressure in veins is relatively low and, particularly in the legs and arms, can tend to pool if allowed to backflow. I â¦ n contrast, there is relatively high blood pressure in the arteries, which prevents the need for valves to control backflow.rteries do not need them as the blood in them is being pumped out from the heart under pressure. The pressure it â¦ self prevents backflow. It is interesting to note that veins in the head and upper chest don't have valves either, because blood in them flows under gravity.