Throat and Esophagus
The throat (pharynx) lies behind and below the mouth. When food and fluids leave the mouth, they pass through the throat. Swallowing of food and fluids begins voluntarily and continues automatically. A small muscular flap (epiglottis) closes to prevent food and fluids from going down the windpipe (trachea) toward the lungs, and the back portion of the roof of the mouth (soft palate) lifts to prevent food and fluids from going up the nose.
The esophagus--a thin-walled, muscular channel lined with mucous membranes--connects the throat with the stomach. Food and fluids are propelled through the esophagus not by gravity but by waves of rhythmic muscular contractions, called peristalsis. At either end of the esophagus are ring-shaped muscles (the upper and lower esophageal sphincters), which open and close. The esophageal sphincters normally prevent the contents of the stomach from flowing back into the esophagus or throat.
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