The pulmonary trunk, also known as the main pulmonary artery (mPA) or truncus pulmonalis is the sole arterial output from the right ventricle and delivers deoxygenated blood to the lungs.
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Gross anatomy
The pulmonary trunk is approximately 50 mm long and 30 mm wide. Some authors use 29 mm in males and 27 mm in females as the upper limit of normal 1,5 however absolute size varies between individuals.
The main pulmonary artery arises as a direct superior continuation of the right ventricular outflow tract from which it is separated by the pulmonary valve. As it ascends, it slants posteriorly and to the left of the ascending aorta. Together 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 to divide into the two main pulmonary arteries: the longer right pulmonary artery and the shorter left pulmonary artery. The division occurs in the concavity of the aortic arch, anterior to the left main bronchus and to the left of the carina.
The left coronary artery passes between the pulmonary trunk (on the left) and the auricle of the left atrium.
Clinical importance
main pulmonary trunk diameters are used in the evaluation of pulmonary dilatation and pulmonary hypertension, however the aortopulmonary ratio >1 is a more accurate determinant of dilatation and pulmonary hypertension in the appropriate clinical context and if there are no confounding factors 8
the common sheath of the ascending aorta and the pulmonary trunk forms a space into which a ruptured ascending aortic aneurysm can bleed and compress the relatively low-pressure pulmonary arteries, causing obstructive right heart failure 9