The pulmonary trunk arises from the base of the right ventricle of the heart. After passing behind the ascending aorta, it splits up into the left and right pulmonary arteries to provide blood for oxygenation in the lungs.
This article will discuss the anatomy and function of the pulmonary trunk.
|Origin||Conus arteriosus of right ventricle|
|Branches||Left and right pulmonary arteries|
|Supply||Delivers deoxygenated blood to the lungs via pulmonary arteries|
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.
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 ascending 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.
Expand and test your knowledge with our learning materials to master the surrounding structures of the heart and the main structures of the cardiovascular system.
Patent ductus arteriosus (PDA)
Failure of ductus arteriosus closure after birth causes oxygenated blood to flow from the aorta back towards the pulmonary trunk and therefore into the pulmonary circulation. PDA is one of the most common congenital heart defects and shows higher prevalence in premature infants.
Symptoms depend on the scale of the remaining opening: Smaller openings have low functional capacities and usually remain without symptoms. More severe, hemodynamically relevant cases lead to a left-to-right shunt and put additional strain on the left ventricle. This can cause heart insufficiency and subsequently blood deficiency in the systemic circulation.
Peripheral body regions receive lower perfusion and the children can present with cold extremities, quick fatigue and an altered postnatal nutrition and growth leading to organ failure.
Treatment in preterm infants involves fluid restriction, "watchful waiting", pharmacologic management and surgical ligation.