Pulmonary artery: Pulmonary artery is the large blood vessel arising from the right ventricle (lower muscular chamber of the heart). It takes deoxygenated blood from the heart to the lungs for oxygenation. It is guarded by the pulmonary valve which prevents backflow of blood into the right ventricle when it relaxes after contraction. Pulmonary artery divides into right and left branches to either lung.