The heart is a strong organ in many creatures, which siphons blood through the veins of the circulatory system. The siphoned blood conveys oxygen and supplements to the body, while conveying metabolic waste, for example, carbon dioxide to the lungs. In people, the heart is roughly the size of a shut clench hand and is situated between the lungs, in the center compartment of the chest. In people, different vertebrates, and feathered creatures, the heart is partitioned into four chambers: upper left and right atria and lower left and right ventricles. Commonly the correct chamber and ventricle are alluded together as the correct heart and their left partners as the left heart. Fish, conversely, have two chambers, a chamber and a ventricle, while reptiles have three chambers. In a solid heart blood streams one route through the heart because of heart valves, which forestall reverse. The heart is encased in a defensive sac, the pericardium, which additionally contains a modest quantity of liquid. The mass of the heart is comprised of three layers: epicardium, myocardium, and endocardium.