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Mittal RK. Motor Function of the Pharynx, Esophagus, and its Sphincters. San Rafael (CA): Morgan & Claypool Life Sciences; 2011.

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Motor Function of the Pharynx, Esophagus, and its Sphincters.

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Introduction

Function of the esophagus is relatively straightforward: to transport swallowed bolus into the stomach and, infrequently, to allow retrograde flow of stomach contents into the esophagus and mouth during belching, regurgitation, and vomiting. In order to meet these functional needs, the design of the esophagus is simple, it is a relatively straight muscular tube that is guarded at the two ends by an upper and a lower esophageal sphincter. Following a voluntary act of swallow the two sphincters relax and open, and a wave of sequential inhibition followed by sequential contraction, i.e., peristalsis, sweeps behind the bolus autonomously through the entire length of the esophagus. Closure of upper and lower esophageal sphincter occurs following passage of peristaltic contraction at each site, respectively. Motor events during retrograde transport, i.e., regurgitation and vomiting, are distinct from swallowing; relaxation of the lower esophageal sphincter occurs first, followed by “retrograde peristalsis in the longitudinal muscle and relaxation of the upper esophageal sphincter.” Unlike most of the gastrointestinal tract where motor events are completely autonomous, neuromuscular control mechanisms of the esophagus and its sphincters require seamless coordination between the volitional and autonomous components of the central nervous system and enteric nervous system located in the wall of the esophagus. Volitional component resides in the cerebral cortex and autonomous component in the brain stem. Muscles of the esophagus, skeletal in the upper part and transition into smooth muscles in the lower part, add complexity to the neural control mechanism. Disturbances of esophageal peristalsis and lower esophageal sphincter cause difficulty in swallowing (dysphagia) and esophageal pain. Detailed pathophysiology of esophageal motor disorders is beyond the scope of this book; however, observations that provide important insights into the physiological function will be discussed.

Copyright © 2011 by Morgan & Claypool Life Sciences.
Bookshelf ID: NBK54286

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