Blood flow through the heart begins with the right heart which receives blood from the body and sends it to the lungs. And the left heart which receives if from the lungs and pumps it into the body.
In the right heart, systemic blood enters the the right atrium. It passes through the tricuspid valve into the right ventricle. Blood is pumped by the right ventricle through the pulmonary valve and into the pulmonary artery which supply the lungs with deoxygenated blood.
Blood returns from the pulmonary system to the left atrium to begin flow through the left heart. From the left atrium, blood passes through the mitral valve into the left ventricle. Blood is pumped by the left ventricle through the aortic valve and into the aorta. Coronary arteries branch first off the aorta to supply the heart with freshly oxygenated blood.
Blood returning from the wall of the heart enters the coronary sinus that empties into the right atrium along with blood from the systemic circulation in the superior and inferorior vena cavae, beginning the cycle once again.
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