Name a structure in the human digestive system, other than teeth, which is involved in mechanical digestion.

• A. Liver
• B. Tongue
• C. Stomach
• D. Small intestine

Answer: (B)

Mechanical digestion is the physical handling and breakdown of food, not enzymatic changes. The tongue is a muscular, highly mobile organ in the mouth that actively moves food around, presses it against the teeth to aid grinding, mixes it with saliva, and shapes it into a bolus for swallowing. This direct, hands-on manipulation is exactly what mechanical digestion entails, so the tongue is the best example of a structure involved in mechanical digestion aside from the teeth themselves. The liver isn’t involved in physical breakdown, and while the stomach and small intestine do mechanical mixing later in the digestive tract, the tongue’s role in the mouth shows the primary, immediate mechanical action on food.