Farmer says the fact gator lungs still had unidirectional flow after being removed shows unidirectional airflow is caused by aerodynamic valves within the lungs, and not by some other factor, like air sacs or the liver, which acts like a piston to aid breathing.
Two very large apertures in the dorsal wall of the mesobronchium gave rise to two very large canals, the ectobronchi. Precapillary arteries a are located in the periphery while postcapillary veins lv line the lumen.
The discovery and its implications for our understanding of the development of life on Earth millions of years ago are detailed in the Jan. Archosaurs evolution tree Bird respiratory system The avian respiratory system is different from that of other vertebrates, since it consists of small rigid lungs plus nine flexible air sacs.
The arrowhead indicates one of the terminal interbronchial openings. Farmer goes one step further and argues that the system would have allowed archosaurs to outcompete synapsids — the ancestors of mammals — following the end-Permian mass extinction.
In this manner, the apicoperipheral convergence zone was extended throughout the periphery of the apical lung Fig.
Next, the airflow in the CVB during normal breathing was monitored in six alligators. This last test also allowed the characterization of the flow in the parabronchi, confirming that it is unidirectional.
Although superficially birds and crocodilians have little in common, their cardiopulmonary systems are similar, particularly the embryonic forms Locy and Larsell, ; Broman, ; Holmes, ; Seymour et al.