The deoxygenated blood enters the heart through right atrium, then go to the right ventricle. It passes through pulmonary artery and goes to the lungs where in the exchange of gasses takes place specifically at the alveoli it removes the carbon dioxide in the blood and replaces with oxygen. Then the oxygenated blood then pass through pulmonary vein and eters the heart through left atrium, the to the left ventricle and to the aorta to all parts of the body