The pulmonary trunk and its branches

The pulmonary trunk (truncus pulmonalis) is 30 mm in diameter and emerges from the right ventricle of the heart, from which it is separated by its valve. The beginning of the pulmonary trunk and, accordingly, its opening are projected onto the anterior chest wall above the attachment site of the cartilage of the third left rib to the sternum. The pulmonary trunk is located in front of the other large vessels of the base of the heart (aorta and superior vena cava). To the right and behind it is the ascending part of the aorta, and to the left is the left auricle of the heart. The pulmonary trunk, located in the pericardial cavity, is directed in front of the aorta to the left and behind and at the level of the fourth thoracic vertebra (cartilage of the second left rib) it divides into the right and left pulmonary arteries. This place is called the bifurcation of the pulmonary trunk (bifurcation trunci pulmonalis). Between the bifurcation of the pulmonary trunk and the aortic arch there is a short arterial ligament (ligamentum arteriosum), which is an overgrown arterial (Botallo's) duct (ductus arteriosus).

The right pulmonary artery (a.pulmonalis dextra) with a diameter of 21 mm follows to the right to the hilum of the right lung behind the ascending part of the aorta and the terminal part of the superior vena cava and in front of the right bronchus. In the area of the hilum of the right lung in front of and below the right main bronchus, the right pulmonary artery divides into three lobar branches. Each lobar branch in the corresponding lobe of the lung in turn divides into segmental branches. In the upper lobe of the right lung, there is an apical branch (r.apicalis), posterior descending and ascending branches (rr.posteriores descendens et ascendens), anterior descending and ascending branches (rr.anteriores descendens et ascendens), which follow into the apical, posterior and anterior segments of the right lung.

The branch of the middle lobe (rr.lobi medii) is divided into two branches - lateral and medial (r.lateralis et r.medialis).

These branches go to the lateral and medial segments of the middle lobe of the right lung. The branches of the lower lobe (rr.lobi inferioris) include the superior (apical) branch of the lower lobe [r.superior (apicalis) lobi inferioris], which goes to the apical (upper) segment of the lower lobe of the right lung, as well as the basal part (pars basalis). The latter is divided into 4 branches: medial, anterior, lateral and posterior (rr.basales medialis, anterior, lateralis et posterior). They carry blood to the basal segments of the lower lobe of the right lung of the same name.

The left pulmonary artery (a.pulmonalis sinistra) is shorter and thinner than the right one, passes from the bifurcation of the pulmonary trunk along the shortest path to the gates of the left lung in a transverse direction in front of the descending part of the aorta and the left bronchus. On its way, the artery crosses the left main bronchus, and at the gates of the lung it is located above it. According to the two lobes of the left lung, the pulmonary artery divides into two branches. One of them breaks up into segmental branches within the upper lobe, the second - the basal part - with its branches supplies blood to the segments of the lower lobe of the left lung.

The branches of the upper lobe (rr.lobi superioris) are directed to the segments of the upper lobe of the left lung, which give off the apical branch (r.apicalis), the anterior ascending and descending (rr.anteriores ascendens et descendens), posterior (r.posterior) and lingual (r.lingularis) branches. The superior branch of the lower lobe (r.superior lobi inferioris), as in the right lung, goes to the lower lobe of the left lung, to its upper segment. The second lobar branch - the basal part (pars basalis) is divided into four basal segmental branches: medial, lateral, anterior and posterior (rr.basales medialis, lateralis, anterior et posterior), which branch out in the corresponding basal segments of the lower lobe of the left lung.

In the lung tissue (under the pleura and in the area of the respiratory bronchioles), small branches of the pulmonary artery and bronchial branches extending from the thoracic part of the aorta form systems of interarterial anastomoses. These anastomoses are the only place in the vascular system in which blood can move along a short path from the systemic circulation directly to the pulmonary circulation.

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