The pulmonary artery arises from the infundibulum of the right ventricle of the heart, passes posteriorly and slightly upwards, and below the aortic arch divides into left and right pulmonary arteries. The right pulmonary artery passes posteriorly and near the hilum divides into upper, middle and lower branches, supplying the upper, middle and lower pulmonary lobes. The left pulmonary artery passes posterosuperiorly, enters the hilum of the left lung and divides into upper and lower branches, which supply the superior and inferior lobes. Further, these branches divide into pulmonary capillaries that form a network around the alveoli. The pulmonary veins are two on each side and they carry oxygenated blood from the lungs to the heart. The pulmonary veins arise from the pulmonary capillaries that join together and form a single trunk. They originate from each lung at the hilum and drain into the left atrium of the heart. On their course, the pulmonary veins also receive the bronchial veins.