Cardiac and cricopharyngeal sphincter thresholds in the cat

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Abstract
In order to elucidate the relative importance of extrinsic and intrinsic factors in the mechanism of cardiac sphincter closure, the effect of various surgical manipulations on opening threshold of this sphincter to increased intragastric pressure was evaluated. The experimental results show that the major mechanism in cats is one of intrinsic smooth muscle contraction. The phrenoesophageal membranes appear to play a minor role in producing a passive-type crural constriction while the gastroesophageal angle was found to be of no importance in sphincter closure. Thresholds of the upper esophageal sphincter to increased intraesophageal pressure were found to be approximately twice as great as those of the cardiac sphincter to increased intragastric pressure.