Blood enters the heart at the right atrium. The right atrium contracts, forcing blood through the tricupsid valve into the right ventricles. Then the right ventricles contracts, pushing the blood through the pulmonary semi-lunar valve into the pulmonary artery. The pulmonary artery transports blood from the lungs, receiving oxygen. Then, pulmonary veins take the oxygenated blood to the left atrium. Blood is then forced through the bicuspid valve into the left ventricles. The left ventricles is the major pump that sends the blood out to the body. The left ventricles contracts sending the blood through the aortic semi- lunar valves and into the aortic. The aortic and its branches carry the blood to all the tissues (including fingertips) of the body. Veins take the deoxygenated blood from these parts of the body back to the heart- to the superior and interior vena cave and into the right atrium.
