Mechanics of swallowing. Cutaway diagrams showing the process of swallowing. At left the mouthful of food (the bolus, green) is being pushed to the back of the mouth by the tongue. At right, the contraction of muscles in the throat have pushed the tongue right up against the roof of the mouth, and folded the epiglottis over the entrance to the trachea. This prevents food from entering the lungs. The bolus is passing the epiglottis and is entering the oesophagus. In the oesophagus, smooth muscle contractions take the food down to the stomach (not seen).