Functional Morphology of the Lungs of the Nile Crocodile, Crocodylus Niloticus: Non-Respiratory Parameters

The complex, multicameral lungs of the Nile crocodile are characterized by rows of tubular chambers, which in cranial and ventral lung regions are broad and sac-like. The inner surface of the chambers is enhanced by cubicles (ediculae), the capillary-bearing walls of which are often perforated. Extrabronchial communication among chambers is infrequent. The ediculae end in a network of myoelastic trabeculae, which face the central lumen of the chambers. The trabecular epithelium is similar to that of mammalian bronchi and contains isolated endocrine-like cells basally, whereas the edicular epithelium is similar to that of other reptiles and of mammals. The distribution of non-vascular smooth muscle, 64% in trabeculae and 36% in interedicular walls, is consistent with the hypothesis that these two antagonistically oriented muscle groups interact to effect lung patency. The volume-specific lung compliance is similar to that of much simpler, unicameral gekko lungs, implying that lung compliance is a function of parenchymal structure and not of primary structural type.