Final answer:
The stomach is involved in both mechanical and chemical digestion. It mechanically breaks down food through muscular contractions and churning, and chemically by secreting gastric acid and enzymes like pepsin.
Step-by-step explanation:
Functions of the Stomach in Digestion
The stomach has multiple roles in digestion, including mechanical digestion and chemical breakdown of food. During the mechanical digestive process, the stomach churns food to break it into smaller pieces. This action is facilitated by waves of muscle contractions known as peristalsis. The stomach's muscular walls are designed to perform this mixing action that helps to expose more of the food's surface area to the stomach's digestive juices.
Chemically, the stomach secretes gastric acid rich in hydrochloric acid, which lowers the pH of the stomach contents, enabling the digestion of proteins by pepsin -- an enzyme that is most effective in acidic conditions. Additionally, the stomach secretes mucus to protect its lining from the corrosive effects of gastric acid. It is in the stomach where the transformation of solid food into a semi-fluid mixture called chyme occurs, allowing for further digestion in the small intestine.