Meeting Abstract
We have known for a long time that the lungs of birds contain aerodynamic valves and one way airflow through most of their conducting airways, and more recently that crocodylians and some lizards also have unidirectional flow. These latter data raise questions about the full phyletic distribution of aerodynamic valves and the functional significance of these patterns of flow. Here we present data on patterns of airflow in the lungs of a turtle, the red-eared slider (Trachemys scripta). The pattern is distinct from the pattern observed in archosaurs and lizards. The lung consists of four, large lateral chambers associated with smaller medial chambers and a broad intrapulmonary bronchus that makes a zigzag pattern through the lung. Using an endoscope that was implanted into the lateral chambers, we visualized the movement of insufflated aerosolized lipids. In the lateral chambers, most of the flow occurred during inspiration, with flow sometimes completely stopping, and generally slowing during expiration. The particles moved in a clockwise direction in the left lung and a counterclockwise direction in the right lung, in dorsal view. CFD simulations of flow show that the gases are moving back and forth between medial and lateral chambers in a transverse figure eight. Fresh air first moves into the most cranial chambers and them makes its way caudad with subsequent inspirations. On exhalation, flow exits in a straighter path along the intrapulmonary bronchus. We found no evidence of intercameral perforations. Measurements of the pressure drop across the lateral chambers at a constant volume of flow but in opposite directions indicates there is greater resistance to flow during inspiration than expiration, and the ratio (diodicity) compared favorably to man-made micro-Tesla valves. The functional significance of this pattern of flow is currently unknown. Funded by NSF IOS CAREER-1055080.
