The pulmonary trunk is a large artery which carries venous blood from the heart right ventricle into the lungs. It is the only artery in the body which conveys deoxygenated blood. It measures between 5 to 6 cm in length and around 2.5 cm in width. It divides into two smaller artery; the right and the left pulmonary artery.
The pulmonary trunk originates from the pulmonary orifice of right ventricle as a continuation of the infundibulum. Its first portion ascends from right to left in front, and to the left of the ascending aorta. Then it curves around the ascending aorta. When it is under the arch of aorta, it divides into the left pulmonary artery and the right pulmonary artery. Each of these arteries travels into the hilum of the corresponding lung.
The pulmonary trunk right artery is a little longer and wider than the left and passes transversely from left to right behind the ascending aorta and superior vena cava, and in front of the right bronchus; then in the root of the right lung, it forks into three branches, each entering the hilum of the corresponding lobe of the right lung. The left artery, on the other hand, also runs transversely, but from right to left in front of ascending aorta and left bronchus; in the root of the left lung, it divides into two branches, which enter the hilum of the corresponding lobe of the left lung.
A fibromuscular band, called ligamentum arteriosum, stretches from the angle of division of the pulmonary trunk to the anterior surface of the concavity of the arch of the aorta. This band is a fibrous remnant of the ductus arteriosus, which, during the intrauterine period, drains most of the blood from the pulmonary trunk into the aorta. After birth, it gets atrophied and closed up to become the ligamentum arteriosum.
Below, image of human heart showing the pulmonary trunk.
Pulmonary trunk in anatomical context of rib cage.
