How the human heart works

Our Heart is about the size of a fist divided into four chambers namely two ventricles and two atria, as discussed above. There are one ventricle and one atrium on the left side and the other atrium and ventricle towards the right side. The ventricles are the chambers that pump blood and atria are the chambers that receive blood. The  deoxygenated blood received to right atrium from:
* The superior vena cava is released into the veins of the upper arms and organs.
* The inferior vena cava that leaves blood from the veins of legs and lower organs.
* The coronary sinus, that leaves deoxygenated blood from the heart.
The right ventricle pumps the blood to the lungs for re-oxygenation when it gets filled  up by the pulmonary arteries. The right semilunar valves close and prevents the blood from the pulmonary veins after blood passes through the pulmonary arteries. Then the oxygenated blood is received by the left atrium from the lungs via pulmonary veins.