The site of origin of nonconfluent pulmonary arteries from a common arterial trunk or from the ascending aorta: its morphological significance.

There are three possible embryological derivatives for nonconfluent pulmonary arteries which arise from a common arterial trunk or from the ascending aorta. We considered the feasibility of identifying these derivatives on the basis of the site of origin. We examined 15 specimens, in which both pulmonary arteries arose by separate orifices from a common arterial trunk (persistent truncus arteriosus), and 3 specimens, in which one pulmonary artery arose from the ascending aorta, the other being connected to the morphologically right ventricle (hemitruncus). Measurements were made for both the upper and lower margins of the orifices of the pulmonary arteries and then expressed as a percentage of the length of the ascending common trunk or aorta. The position of origin ranged from 39 to 100% for the upper margin and from 17 to 90% for the lower margin, without significant difference between left and right arteries. Since the range varied so widely, we contend that it is not possible to make a morphological identification of the pulmonary artery under consideration simply on the basis of the location of the site of origin.