-two circuits joined together ( lungs / res of body)
right ventricle pumps deoxygenated blood to the lungs to get oxygen. blood then returns to heart (first one)
left ventricle pumps oxygenated blood around all the other organs of the body. the blood give up it oxygen at the body cells and deoxygenated blood returns to the heart to be pumped out to the lungs again (second one)