The movement of the jaw enables the teeth to grind food into small fragments. The mandible, or jawbone, is the only bone in the head that moves, and the points where the temporal bones connect to the mandible make up the only two movable joints in the head. The official name for chewing is mastication. This is the first step in mechanical digestion.
The tongue manipulates the chewed food into a small mass called a bolus, then moves it to the oropharynx. The next steps are involuntary: the bolus passes through the pharynx, the epiglottis closes off the trachea and directs the bolus down the esophagus, and peristaltic waves move the bolus into the stomach.
A description of the oral cavity from the 1918 edition of Gray's Anatomy of the Human Body.
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