The heart is situated in the center of the chest. It is approximately the size of a closed fist of an individual's hand. It is positioned in the middle of the chest cavity. It is more aligned to the left, tucked in between the two lungs.

The heart, a hollow muscular organ, is a pump house of the body. As the name suggests, its underlying function is to pump blood into the lungs for oxygenation and then carry this blood to the whole body. In simple words, the heart collects oxygen-depleted blood from the body pumping into the lungs, where it picks up the oxygen and drops off the carbon dioxide. The heart then collects the oxygen-enriched blood and sends it to the various parts of the body. 

The arteries and veins are the carriers of the blood. The arteries carry the pure blood (oxygenated blood) from the heart to various parts of the body, whereas the veins bring the impure blood (unoxygenated blood) from the various parts of the body, back to the heart. 
 

The heart consists of four chambers, two on both sides i.e. left and right side. Each side consists of an atrium, which are the small receiving chambers, and ventricles, which are big pumping chambers. So the heart consists of right atrium and right ventricle, which receive blood from the whole body and again pump it into the lungs. While the left atrium and left ventricle, receive oxygenated blood from the lungs and pump it into the aorta, which are the main arterial highway of our body.