It is approximately 50 mm long and 30 mm wide (most authors use 29 mm width as the cut-off of normal 1).
It arises as a direct superior continuation of the right ventricular outflow tract, separated by the pulmonary valve. As it ascends it slants posteriorly and to the left of the ascending aorta. With the ascending aorta, the pulmonary trunk is invested in a common sheath of serous visceral pericardium, anterior to the transverse pericardial sinus.
At the level of the transthoracic plane, the trunk emerges from the fibrous pericardium and divides into the longer right and shorter left pulmonary arteries in the concavity of the aortic arch, anterior to left main bronchus and to the left of the carina.