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The pulmonary trunk is the first and largest vessel within the pulmonary arterial tree. It passes deoxygenated blood from the heart to the lungs. It originates from the right ventricle and passes superiorly and posteriorly for about 4-5 cm. During this course, it is ensheathed by the pericardial sac and initially is anterior to the ascending aorta.
At the level of the inferior margin of the carina, approximately T5, the pulmonary trunk divides into right and left pulmonary arteries. At this point its relations are:
inferior: left atrium
þ superior: aortic arch