All of the blue-colored blood vessels on a blood flow diagram show passages carrying deoxygenated blood from the heart to the lungs, while all of the red-colored passages show oxygenated blood being circulated throughout the body. The heart's right chambers pump deoxygenated blood, while the left chambers pump oxygenated blood.
The two largest blue blood vessels located nearest the heart are the superior and inferior vena cava. These blood vessels carry deoxygenated blood throughout the body to the heart. Once in the heart, blood flows from the right atrium, through the tricuspid valve, into the right ventricle and through the pulmonary valve. After leaving the heart, blood flows through the pulmonary arteries and into the lungs.
In the lungs, red blood cells absorb oxygen inhaled by the person before traveling back to the heart through the pulmonary veins. Oxygenated blood enters the heart at the left atrium, goes through the mitral valve into the left ventricle and finally passes through the aortic valve. After passing through the aortic valve, blood enters the aorta. From the aorta, blood flows into the body's arteries, including the large left and right carotid arteries. Once blood travels throughout the body, it works its way back to the superior and inferior vena cava, and the entire process repeats itself.