The pulmonary arteries carry deoxygenated blood from the right ventricle into the alveolar capillaries of the lungs to unload carbon dioxide and take up oxygen. These are the only arteries that carry deoxygenated blood and are considered arteries because they carry blood away from the heart. The short, wide vessel branches into the left and right pulmonary arteries that deliver deoxygenated blood to the respective lungs. Blood first passes through the pulmonary valve as it is ejected into the pulmonary arteries.