A red blood cell which carries carbon dioxide and is deoxygenated starts from the right atrium will pass to the right ventricle and then pumps through the pulmonary artery to the lungs. In the lungs, it will leave carbon dioxide and combines with oxygen. It will return to the left atrium through the pulmonary veins then to the left ventricle. The left ventricle will pump it through the aorta to the arteries and then to the arterioles of the foreleg. It will then enters the blood capillaries of the foreleg to get connected with its cells and gives it oxygen and nutrients and take away carbon dioxide. It will then back to the heart through vneules, veins and then the vena cava to enter the right atrium.