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 saclike. 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 volumespecific 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.