What are the components of a circulatory system in the human body?

The heart pumps blood around the body. Blood is carried by blood vessels: arteries and veins. Arteries carry blood away from the heart, and then divide into smaller arterioles. Arterioles carry blood into capillaries, which provide tissues and organs. Oxygen is removed from the blood as tissues require. The deoxygenated blood is carried into venules and veins and then back to the heart. This is the systemic circulation of the body. The heart consists of four chambers: left atrium, left ventricle, right ventricle and right atrium. Deoxygenated blood returns to the right atrium via the vena cavae. Blood goes into the right ventricle and is pumped to the lungs via the pulmonary arteries. Blood picks up oxygen at the lungs. The oxygenated blood returns to the left atrium via the pulmonary veins and then travels to the left ventricle. Blood is ejected to the rest of the body from the left ventricle via the aorta.