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).
The pulmonary veins enter the left atrium. When the left atrium relaxes, the oxygenated blood drains into the left ventricle through the left AV valve. This valve is also called the bicuspid valve because it has only two flaps in its structure. Now the heart really squeezes.