Blood coming from all parts of the body is received by the (1)______ of the heart by way of the blood vessel called (2)_____. Contraction of the right atrium send blood to the (3)_________. At this point, the (4)_______ valves are open. Contraction of the right ventricle forces blood to the (5)______ for oxygenation by way of the (6)________. At this point, the (7)_______ valves are open, while the (8)_______ valves are closed to prevent the back flow of blood in the right atrium.

From the lungs, oxygenated blood goes back to the (8)______ of the heart via the blood vessels called (9)_______. Contraction of the left atrium forces blood to the (10)_______. At this point, the (11)________ are open. Contraction of the left ventricle pumps blood to (12)_______ by way of the (13)________, the largest artery. At this point, the (14)_______valves are open while the (15)_______ are closed to prevent the backflow of blood in the left atrium.​