The root of the lung is a general term for all the structures entering and exiting the lung, including the main bronchitis, pulmonary artery, pulmonary veins, bronchial artery, bronchitis vein, nerves, lymphatic vessels, and lymph nodes, connected by loose connective tissue and formed by thickened pleurae.

The root of the lung is about 10 mm long. On the left side, the root of the lung descends from the upper to the lower lung artery, left bronchitis, and inferior pulmonary vein; on the right side, it is followed by the upper lobe bronchitis, pulmonary artery, right main bronchitis, and inferior pulmonary vein. From front to back, both sides are successively the superior pulmonary vein, pulmonary artery, and main bronchitis.

Intrapericardial pulmonary vessels

When lung lesions are close to the lung root and cannot be sufficiently supplied with vascular trunks, or in lung cancer patients where the swollen lymph nodes surround the lungs, and the vessels cannot be seen, the dispersion of the pulmonary arteries and veins within the pericardium can increase the resection rate and the safety of surgery, preventing blind anatomical dissection that may cause hemorrhage. The dispersion of pulmonary vessels within the pericardium requires an understanding of the anatomy of the intrapericardial pulmonary vessels: the right pulmonary artery runs from left to right behind the ascending aorta, then crosses behind the superior vena cava and enters the pericardial cavity, with three-quarters of its circumference covering the serous membrane. The right pulmonary vein has three-quarters of its circumference covered by the serous membrane in the upper part of the pericardium, while the lower part of the right pulmonary vein is covered by only one-third of its circumference by the serous membrane, with approximately 3% of patients having the right superior and inferior pulmonary veins merging within the pericardium to enter the left atrium. The left pulmonary artery has one-half of its circumference covered by the serous membrane, and it is necessary to incise the serous membrane on both sides when dispersing the left pulmonary artery. The superior pulmonary vein has three-quarters of its circumference covered by the serous membrane, and the inferior pulmonary vein is easily dispersible within the pericardium, with 90% of its circumference covered by the serous membrane, and approximately 25% of patients have the superior and inferior pulmonary veins merging within the pericardium to enter the left atrium.

Main bronchus

It is a segment of the tube from the bronchial bifurcation to the lungs, dividing into left and right main bronchus. Its structure is similar to that of the bronchus, mainly composed of bronchial cartilage rings, smooth muscle, and connective tissue. See bronchus, left and right main bronchus entries.

Pulmonary artery

The pulmonary trunk is a short and thick aorta, originating from the arterial cone of the right ventricle and ascending obliquely to the left and posteriorly. It first lies in front of the root of the ascending aorta, then to its left, below the aortic arch, approximately at the level of the fifth lumbar vertebra, and divides into left and right pulmonary arteries. The left pulmonary artery is shorter and wildly extends to the left, passing in front of the left main bronchus to reach the left hilum, dividing into two branches entering the upper and lower lobes of the left lung. The right pulmonary artery is longer and wildly extends to the right, reaching the right hilum only after passing through the ascending pulmonary artery and behind the superior vena cava, dividing into three branches entering the upper, middle, and lower lobes of the right lung. The branches of the left and right pulmonary arteries repeatedly branch within the pulmonary substance, accompanying the bronchial branches, and finally reach the bronchial wall, forming a dense capillary network. The pulmonary artery transports venous blood rich in carbon dioxide. There is a fibrous cord in the middle slightly to the left of the bifurcation of the pulmonary trunk and the outer margin of the aortic arch, known as the arterial ligament (arterial ligaments). It is the site after the closure of the ductus arteriosus during the fetal stage. The ductus arteriosus closes shortly after birth. If it remains patent for a long time, it is called patent ductus arteriosus, a congenital heart disease.