Anatomical backgrounds on gas exchange parameters in the lung

Figure 3 Secondary lobule and acinus. Secondary lobule of Miller is defined by the area supplied by a lobular bronchiole while the acinus of Loeschcke is defined by the area supplied by a terminal bronchiole. Acinus of Aschoff is the area supplied by a first-order respiratory bronchiole. Secondary lobule of Miller is surrounded by fibrous connective tissue forming interlobular septum. In acini of Loeschcke and Aschoff, there are three important interstitial tissues, including peripheral interstitium, alveolar interstitium forming alveolar septum, and axial interstitium spirally surrounding airways, which begins at the alveolar duct extending to the hilum. Axial interstitium and alveolar interstitium are joined via intra-parenchymal interstitium and all interstitial tissues are in a serial linkage. Modified from ref[2].