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).
Likes history and psychology. Most veins do not have valves. The reason being that the pressure on the system is sufficient to propel blood back to the heart. It is the veins further away from the heart in the lower limbs that have valves. This is to ensure that blood only flows in one direction ie back to the heart.