Human lungs are divided into ve lobes, the right lung having three lobes-the right upper, right middle, and right lower lobes-and the le lung having two lobes-the le upper and le lower lobes. In men, the average weight of both lobes is about 850 g, and in women, 750 g. e proximal bronchial branches divide these lobes into 10 bronchopulmonary segments. ese segments are made up of lobules which represent the smallest anatomical compartment of the lung that is macroscopically visible. Lobules are 1 to 2 cm in diameter, polygonal, and bound by complete or incomplete connective tissue interlobular septa. ey are visible immediately beneath the pleura when outlined by septal lymphatics, especially when the latter contain anthracotic pigment or soot as occurs in smokers (Figure 4.1). Lobules are not well dened in the central regions of the lung because of age-related changes. Each lobule is made up of 3 to 30 acini and is served by centrally located terminal bronchiole-arterial bundles with pulmonary veins transporting blood away in the interlobular septae (Figure 4.2). e visualization of pulmonary lobules has importance in the correlation of radiological ndings, especially from high-resolution computed tomography (e.g., interlobular septae are widened and accentuated in pulmonary edema, becoming visible radiologically as Kerley B lines).