Have you ever noticed how your mouth can start "watering" at the sight of your favorite food? That's because digestion begins in the mouth. The teeth grind the food and mix it with saliva to form a kind of ball, called a bolus. During the mixing, an enzyme called "salivary amylase" starts breaking down carboyhydrates. Once the food is soft and relatively flexible, the tongue pushes it to the back of the mouth and swallows it down the esophagus.