The pulmonary circulation comprises the right ventricle, pulmonary artery, pulmonary arterioles, pulmonary capillaries, pulmonary venules, and the pulmonary vein. the right ventricle pumps blood towards the lungs, capillaries are the point in which gas exchange occurs. exchange occurs between the interstitial fluids of the alveoli and the blood plasma enters the left side of the heart via the left venules entering through the left pulmonary vein into the left atrium, atrial contraction occurs, the blood then enters the left ventricle to then be ejected from the heart via the aorta to be transported around the body.