Activity B: Mechanical and chemical digestion Get the Gizmo ready: Click Reset and Clear screen. Build a system with a Mouth, Salivary gland, Esophagus, Pancreas, and Rectum. Introduction: Before nutrients are absorbed, they must be broken down to their simplest components. Teeth and muscular contractions in the stomach break food down into smaller particles, a process called mechanical digestion. In the meantime, powerful chemicals break down food in a process called chemical digestion. Question: How are nutrients broken down in your digestive system