The trachea divides into the right and left main bronchi at the level of the sternal angle (T4 level). The right bronchus is wider, shorter, and more vertical compared to the left. The right bronchus divides into three lobar bronchi, supplying the right upper, middle, and lower lung lobes respectively. The left bronchus divides into two lobar bronchi, supplying the left upper and lower lobes.

The lung has a unique dual blood supply. The pulmonary artery trunk originates from the right ventricle and gives the right and left pulmonary arteries. The right pulmonary artery passes posterior to the aorta and superior vena cava. The left pulmonary artery courses anterior to the left mainstem bronchus. The pulmonary arteries supply deoxygenated blood from the systemic circulation directly to alveoli where gas exchange occurs. These vessels are large in diameter, but supply blood in a low pressure system.

The bronchial arteries arise directly from the thoracic aorta. These vessels are smaller in diameter, and supply the trachea, bronchial tree, and visceral pleura.

The venous drainage of the lungs occurs from the pulmonary veins. They originate at the level of the alveoli. There are two pulmonary veins on the right and two on the left. These four veins join at or near their junction with the left atrium usually within the pericardium. These veins carry oxygenated blood back to the heart for distribution to the systemic circulation.

The lung is covered superiorly, anteriorly, and posteriorly by pleura. At its inferior border the investing layers come into contact forming the inferior pulmonary ligament that connects the lower lobe of the lung, from the inferior pulmonary vein to the mediastinum and the medial part of the diaphragm. It serves to retain the lower lung lobe in position.