Swallowing.
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   In  the  oral cavity, digestion begins when salivary amylase initiates
   the breakdown of carbohydrates.
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   The  pharynx  is  a  junction that opens to both the esophagus and the
   trachea (windpipe).
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   In  the absence of food, the esophageal sphincter muscle is contracted
   and the epiglottis is up, allowing air to flow through the glottis and
   trachea to the lungs.
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   continue