Journal of Comparative Physiology B

, Volume 157, Issue 3, pp 307–314 | Cite as

Gas exchange and air flow in the lung of the snake,Pituophis melanoleucus

  • Jerry N. Stinner


Gas samples from various regions of the lung were obtained throughout the breathing cycle inPituophis melanoleucus. Changes in CO2 concentration during the interbreath period differed markedly along the length of the lung. In general, the largest and most rapid increases in CO2 tension were measured at the cranial end of the vascular lung. Further caudad in the vascular lung, the increase was slower and did not reach mixed venous CO2 tension before exhalation. In animals exhibiting the lowest breathing frequencies and presumably larger tidal volumes, the region of gas exchange extended into the cranial portion of the air sac. There was little or no change in gas tensions within the remaining caudal regions of the air sac. Measurement of exhaled CO2 and O2 tensions at the nares confirmed the longitudinal gradient in gas exchange and also demonstrated the sequential emptying of the lung. Large regional differences in the ratio of blood flow to alveolar volume are probably responsible for the gradients in lung gases.

Interpretation of N2 clearance curves in terms of two freely communicating compartments demonstrated the presence of a ventilation inequality. Consistent with this was the lack of body wall contractions between breaths while animals were resting. However, just prior to and during activity body wall contractions not associated with breathing often occurred and resulted in pressure excursions in the lung of ca. five mm H2O. In addition, the heart beat results in a pressure change within the lung of ca. 0.2 mmH2O which may be significant in gas mixing.


Breathing Frequency Breathing Cycle Alveolar Volume Clearance Curve Large Tidal Volume 
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Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • Jerry N. Stinner
    • 1
  1. 1.Division of BiologyUniversity of CaliforniaRiversideUSA

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