Blood Vessels of the Lung

• Extends upward from the conus arteriosus of the right ventricle of the heart and carries poorly oxygenated blood to the lungs for oxygenation
• Passes superiorly and posteriorly from the front of the ascending aorta to its left side for about 5 cm and bifurcates into the right and left pulmonary arteries within the concavity of the aortic arch at the level of the sternal angle.
• Has much lower blood pressure than that in the aorta and is contained within the fibrous pericardium.

• Carries deoxygenated blood to the left lung, is shorter and narrower than the right pulmonary artery, and arches over the left primary bronchus.
• Is connected to the arch of the aorta by the ligamentum arteriosum , the fibrous remains of the ductus arteriosus.

• Runs horizontally toward the hilus of the right lung under the arch of the aorta behind the ascending aorta and SVC and anterior to the right bronchus.

• Are intersegmental in drainage (do not accompany the bronchi or the segmental artery within the parenchyma of the lungs).
• Leave the lung as five pulmonary veins, one from each lobe of the lungs. However, the right upper and middle veins usually join so that only four veins enter the left atrium.
• Carry oxygenated blood from the respiratory part (alveoli) of the lung and deoxygenated blood from the visceral pleura and from a part of the bronchioles to the left atrium of the heart. (Gas exchange occurs between the walls of alveoli and pulmonary capillaries, and the newly oxygenated blood enters venules and then pulmonary veins.)

• Arise from the thoracic aorta; usually there is one artery for the right lung and two for the left lung.
• Supply oxygenated blood to the nonrespiratory conducting tissues of the lungs and the visceral pleura. Anastomoses occur between the capillaries of the bronchial and pulmonary systems.

• Receive blood from the bronchi and empty into the azygos vein on the right and into the accessory hemiazygos vein or the superior intercostal vein on the left.
• May receive twigs (small vessels) from the tracheobronchial lymph nodes.