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).
Valves in Veins (Venous Valves) - One way valves in the veins prevent backflow (due to low blood pressure) - Skeletal muscles surrounding the veins squeeze them which pushed the blood up towards the heart. - Standing still for a long time causes fainting.