Pulmonary trunk

Commencing at the pulmonary orifice, which is at a slightly higher level than the aortic orifice, the wide pulmonary trunk arches backwards to the left of the ascending aorta, the two vessels making the gentle spiral enclosed in the common sleeve of serous pericardium in front of the transverse sinus. The trunk passes backwards and emerges from the fibrous pericardium to divide in the concavity of the aortic arch and in front of the left main bronchus into the right and left pulmonary arteries, which enter the lung roots with their corresponding bronchi. The trunk is about 5 cm (2 in) long and most of it lies within the pericardial cavity. Note that the proper name for this vessel is the pulmonary trunk, not the pulmonary artery which is not the name for any vessel; the pulmonary trunk divides into the right pulmonary artery and the left pulmonary artery.