The flow of blood through heart takes place step by step:
(1) Oxygen-rich blood from the lungs comes to the left chamber of the heart, the left atrium, via the pulmonary veins.
(2) When the left auricle contracts, the left ventricle expands and the blood is transferred to it.
(3) On contraction of the left ventricle, the blood is pumped out to the body, through Aorta.
(4) The Aorta branches into vessels which transport blood to the heart and all body parts.
(5) De-oxygenated blood comes from the body to the upper chamber of the heart, the right atrium through large veins called vena cava.
(6) When right atrium is full blood, it contracts and the tricuspid valves open under pressure and the blood are forced into the right ventricle.
(7) When the right ventricle contracts, the blood is pumped into the pulmonary trunk.
(8) The pulmonary trunk divides into the right and left pulmonary artery, each of which carries the blood to the lungs for oxygenation.