The role of the heart is to circulate blood through two pathways: the pulmonary circuit and the systemic circuit.
In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart (the image helps to understand better the parts of it) via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.
It is located underneath the sternum or chest bone, and sits a little to the left. The heart is located between the lungs and lies in front of the backbone.
the size of it is pretty close of a fist.
Now i'm going to talk about a few illnes that can alter the good function of this organ: Coronary artery disease (narrowing of the arteries), Heart attack, Abnormal heart rhythms or arrhythmias, Heart failure, Heart valve disease, Congenital heart disease, Heart muscle disease, Pericardial disease, Aorta disease, Marfan syndrome and Vascular disease.