Antireflux mechanisms

Lower pressures are present in the kitten LES (lower esophageal sphincter) than in the adult cat. The LES pressure depends on stress developed by the LES circular muscle and t/r ratio of thickness to inner radius. Although the kitten develops higher stress than the adult, its thickness/radius ratio is low. This means that although the kitten's circular muscle can contract very well, there is just not enough of it to get the job done. Furthermore, the kitten LES circular muscle is less sensitive to muscarinic excitation. If cholinergic tonus is important in maintaining, or even just modulating LES pressure, this reduced sensitivity would result in reduced intraluminal pressure.