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The Right‐to‐Left Shunt of Crocodilians Serves Digestion

C. G. Farmer, T. J. Uriona, D. B. Olsen, M. Steenblik and K. Sanders
Physiological and Biochemical Zoology: Ecological and Evolutionary Approaches
Vol. 81, No. 2 (March/April 2008), pp. 125-137
DOI: 10.1086/524150
Stable URL: http://www.jstor.org/stable/10.1086/524150
Page Count: 13
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The Right‐to‐Left Shunt of Crocodilians Serves Digestion
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Abstract

Abstract All amniotes except birds and mammals have the ability to shunt blood past the lungs, but the physiological function of this ability is poorly understood. We studied the role of the shunt in digestion in juvenile American alligators in the following ways. First, we characterized the shunt in fasting and postprandial animals and found that blood was shunted past the lungs during digestion. Second, we disabled the shunt by surgically sealing the left aortic orifice in one group of animals, and we performed a sham surgery in another. We then compared postprandial rates of gastric acid secretion at body temperatures of 19° and 27°C and rates of digestion of bone at 27°C. Twelve hours after eating, maximal rates of gastric acid secretion when measured at 19° and 27°C were significantly less in the disabled group than in sham‐operated animals. Twenty‐four hours postprandial, a significant decrease was found at 27°C but not at 19°C. For the first half of digestion, dissolution of cortical bone was significantly slower in the disabled animals. These data suggest the right‐to‐left shunt serves to retain carbon dioxide in the body so that it can be used by the gastrointestinal system. We hypothesize that the foramen of Panizza functions to enrich with oxygen blood that is destined for the gastrointestinal system to power proton pumps and other energy‐demanding processes of digestion and that the right‐to‐left shunt serves to provide carbon dioxide to gastrointestinal organs besides the stomach, such as the pancreas, spleen, upper small intestine, and liver.

Notes and References

This item contains 43 references.

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