 This video will cover the following objective, compare the pulmonary circuit and the systemic circuit. The pulmonary circuit is a system of blood vessels carrying blood to and from the lungs, whereas the systemic circuit is a system of blood vessels carrying blood to and from the rest of the tissues in the body. The pulmonary circuit starts with blood flowing out of the right ventricle into the pulmonary trunk. The pulmonary trunk branches into the pulmonary arteries. The left pulmonary artery carries blood to the left lung. The right pulmonary artery carries blood to the right lung. The pulmonary arteries then carry this deoxygenated blood into the capillaries of the pulmonary circuit. The capillaries are the small blood vessels where gas exchange occurs. Oxygen diffuses into the blood at the pulmonary circuit in the pulmonary capillaries. Then the blood from the pulmonary capillaries that is now oxygen rich drains through pulmonary veins back to the heart at the left atrium. And so the pulmonary circuit essentially begins with the right ventricle and ends with the left atrium. Then the systemic circuit begins with blood flowing out of the left ventricle into the aorta. The aorta then branches into numerous arteries that distribute blood to tissues all through the body. Blood flows into systemic capillaries where nutrients are delivered to tissues. For example, oxygen is one of the major nutrients that is moving out of the blood at the systemic capillaries. And so the concentration of oxygen is much lower in the blood that's draining from the systemic capillaries through veins back to the heart. The inferior vena cava carries blood from the lower parts of the body and the superior vena cava carries blood from the upper body. But both the superior and the inferior vena cava drain into the right atrium. The systemic circuit also includes the coronary circuit which are the blood vessels carrying blood to and from the heart muscle. And so the coronary arteries carry blood from the aorta to capillaries in the myocardium and then cardiac veins drain the blood from the capillaries of the myocardium and the great cardiac vein, middle cardiac vein and lesser cardiac vein all joined together into the coronary sinus and the coronary sinus then drains this deoxygenated blood into the right atrium. And so the systemic circuit essentially begins with the left ventricle and ends with the right atrium.