Omg good question but it is a long process
the human heart is an organ that pumps blood through circulatory system ,supplying oxygen and nutrients to the tissues and removing carbon dioxide and other wastes
the heart pumps blood through two pathways pulmonary circuit and  the system circuit...
The main function of the heart is to pump the blood and circulate it to every single cell of the body employing arteries, veins and capillaries. Its important to mention here that the heart does not do any sort of purification work of the blood, neither it removes carbon dioxide from the blood. Purification work is of lungs. Heart only supplies the blood and hence the oxygen combined with hemoglobin reaches to each and every part of the body.