Vasculature of the Lungs Learning Objectives At the end of this lecture, the student should be able to: 1. Describe the origin, course and termination of Bronchial vessels 2. Discuss the origin, course and termination of pulmonary vessels Lecture Outline Vessels Supplying Lung Blood supply of lungs comprising of two groups of vessels Bronchial Vessels Bronchial Arteries Bronchial Veins Pulmonary Vessels Pulmonary Arteries Pulmonary Veins Bronchial arteries and veins The bronchial arteries and veins constitute the 'nutritive' vascular system of the pulmonary tissues (bronchial walls and glands, walls of large vessels, and visceral pleura). They interconnect within the lung with branches of the pulmonary arteries and veins. Bronchial arteries • The bronchial arteries supply the supporting tissues of the lungs and visceral pleura. • Left bronchial arteries arise from the superior thoracic aorta. • The superior left bronchial artery arises at vertebral level T5 and the inferior left bronchial artery below the left bronchus • The origin of the right bronchial artery is variable; in order of frequency, it may arise • from a right posterior intercostal artery (usually the 3rd), • from a common trunk shared with the left superior bronchial artery, or • directly from the aorta. Bronchial veins • The bronchial veins drain only part of the blood supplied to the lungs by the bronchial arteries, primarily that distributed to or near the more proximal part of the roots of the lungs. • The remainder of the blood is drained by the pulmonary veins, specifically that returning from the visceral pleura, the more peripheral regions of the lung, and the distal components of the root of the lung. • The right bronchial vein drains into the azygos vein • The left bronchial vein drains into the accessory hemiazygos vein or the left superior intercostal vein • Bronchial veins also receive some blood from esophageal veins. Pulmonary Vessels • Each lung has a large pulmonary artery supplying blood to it and two pulmonary veins draining blood from it • The right and left pulmonary arteries arise from the pulmonary trunk at the level of the sternal angle and carry poorly oxygenated blood to the lungs for oxygenation. • Each pulmonary artery becomes part of the root of the corresponding lung and gives off its first branch to the superior lobe before entering the hilum. Pulmonary Arteries • Within the lung, each artery descends postero-lateral to the main bronchus and divides into lobar and segmental arteries. • Consequently, an arterial branch goes to each lobe and broncho-pulmonary segment of the lung, usually on the anterior aspect of the corresponding bronchus. • The arteries and bronchi are paired in the lung, branching simultaneously and running parallel courses. Pulmonary Veins • The pulmonary veins, two on each side, carry well-oxygenated blood from the lungs to the left atrium of the heart . • Beginning in the pulmonary capillaries, the veins unite into larger and larger vessels. • The pulmonary veins run independently of the arteries and bronchi, coursing between and receiving blood from adjacent segments as they run toward the hilum. • The veins from the visceral pleura drain into the pulmonary veins. • The veins from the parietal pleura join systemic veins in adjacent parts of the thoracic wall.