Two components combine to form the lower esophageal sphincters: an intrinsic component and an extrinsic component. The intrinsic portion consists of muscle fibers that respond to molecules called neurohormones that carry signals from the brain. The extrinsic component is a diaphragm muscle that controls the pressure in the lower sphincter. Anything that malfunctions or interrupts the closing of the lower esophageal sphincter can lead to gastroesophageal reflux and changes in the mucus lining of the esophagus.

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