According to About.com, the right ventricle, one of the heart's four chambers, pumps de-oxygenated blood into the main pulmonary artery. From there, the blood is directed into the lungs where it gathers oxygen before going through the pulmonary veins to another chamber, the left atrium.
About.com explains that the left ventricle then pumps blood into the rest of the body through the aorta, an important artery. While performing other functions, the blood also delivers oxygen to body tissues. After blood has circulated, it returns to the heart's right atrium through two veins, "venae cavae." The atria are the upper parts of the heart, while the ventricles are the lower chambers.