The heart is the main organ of the circulatory system. The job of the circulatory system is to transport oxygen and nutrients throughout the body. The heart has 4 chambers. Two of the chambers receive blood and two of the chambers pump blood out of the heart. The heart is also broken up into right and left halves. The right half of the heart receives deoxygenated blood and pumps it to the lungs to get oxygen. The left half of the heart receives oxygenated blood from the lungs and then pumps blood to the body. Nutrients and oxygen are delivered to cells so that growth, reproduction, movement, etc., can continue.
Heart is a pumping organ situated in the thorax. It's covered with the pericardium. The heart consist of 4 chambers. They are: the right ventricle, the right artium, the left ventricle and the left atrium. The heart has the function of pumping blood all throughout the body and it's muscles (cardiac muscles) never get tired. The thickest wall of the heart is the left ventricle's wall. This is because it has the important function of pumping oxygenated blood all over the body via the aorta. So, it's the heart which pumps blood and it's one of the most important.
Function of heart is to circulate blood to all parts of body. It is actually a pair of pumps. A somewhat bigger and stronger pump receives oxygen rich blood from the lungs and circulates it to the whole body. The second pump, which is smaller pump receives the the blood pumped by the first one after it has circulated in the body. This blood received in the smaller pump returns to heart after it has supplied oxygen to the various parts of the body and in exchange absorbed carbon dioxide. This blood is pumped by the heart to lungs, where the blood gives out its carbon dioxide and absorbs oxygen. When the blood cleaned and regenerated by the lung in this way returns to the inlet side of the lager pump, the cycle of blood circulation is completed.