The upper and lower vena cava flow venous blood, the lower vena cava mainly collects the blood returning from the abdominal cavity, the liver, and the veins of the lower extremities, and the upper vena cava mainly collects the blood returning from the veins of the head, neck, and both upper extremities, and all of this returns to the right heart through these two main channels and enters into the pulmonary artery and the lungs. Through the alveoli of the lung tissue and air for gas exchange, the formation of arterial blood, and through the pulmonary veins into the left heart, the formation of arterial blood, will again supply the body’s organs, so that the body’s blood circulation to maintain the normal tissue of nutrient metabolism. Therefore, it is necessary to return venous blood to the right atrium through the upper and lower vena cava, which are two very important blood vessels, draining mainly venous blood after the body through the tissue metabolism.