Pulmonary trunk

Origin and course

The pulmonary trunk has a length of only about 5 cm. It is the direct continuation of the right ventricular outflow tract and starts at the conus arteriosus of the right ventricle. Initially located anterior to the ascending aorta, the vessel runs posteriorly and crosses the ascending aorta to the left.

After its short course, the pulmonary trunk splits into the left and right pulmonary arteries at the level between the T5 and T6 vertebrae. The left pulmonary artery is commonly a direct continuation of the pulmonary trunk's course, while the right pulmonary artery arises almost at a right angle.

Relations

The pulmonary trunk is covered by pericardium and lies in a common sheath with the ascending aorta. Its lumen contains the pulmonary valve which permits the blood to flow from the right ventricle to the pulmonary trunk. The cusps of the pulmonary valve form mild dilations in the pulmonary trunk wall called pulmonary sinuses.

The pulmonary trunk is connected to the descending aorta via the ligamentum arteriosum, a remnant of the obliterated ductus arteriosus (ductus Botalli). In the developing fetus, the ductus arteriosus transports blood directly from the pulmonary trunk into the aorta and bypasses the fetal lungs.

Branches and supply

The pulmonary trunk terminates in the two pulmonary arteries.

• The right pulmonary artery runs underneath the aortic arch and passes behind the superior vena cava to the right lung hilum.
• The left pulmonary artery is shorter than its right counterpart and arches over the left main bronchus before reaching the left lung.

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