Comparative subgross anatomy of lungs. Pleuras, interlobular septa, and distal airways.

There are major species differences in the subgross anatomy of lungs that influence lung function and the reaction to injury. Variations in lobation and in the structure of pulmonary pleuras, interlobular septums, and distal airways are reviewed and tabulated. Thick pleura is usually accompanied by extensive interlobular connective tissue that forms complete interlobular septums in some species but only incomplete septums in others, resulting in functional differences. In some species, terminal bronchioles end by forming respiratory bronchioles, which in turn form alveolar ducts, whereas in other species terminal bronchioles end by directly forming alveolar ducts, resulting in species differences in acini. The methods used and the biological significance are discussed.