The stomach uses both mechanical and chemical processes to break down food.
Mechanical Digestion
- Muscular Contractions: The stomach's muscular walls churn and mix food. These contractions physically break down large food particles into smaller ones. This mixing action also helps combine food with digestive juices.
Chemical Digestion
- Gastric Juices: Glands in the stomach lining secrete gastric juices. These juices contain:
- Stomach Acid (Hydrochloric Acid): This acid helps break down food, particularly proteins, and kills bacteria.
- Enzymes: Specifically, pepsin is an enzyme that starts the breakdown of proteins into smaller peptides.
- Mixing: The stomach's churning action thoroughly mixes the gastric juices with the food, allowing for effective chemical digestion.
Table Summary of Stomach Digestion
| Process | Description | Function |
|---|---|---|
| Mechanical | Stomach muscles contract and churn. | Breaks down food into smaller particles and mixes it with digestive juices. |
| Chemical | Glands in the stomach lining secrete acid and enzymes. | Breaks down food chemically, particularly proteins. |
How the Stomach Works
- Food Entry: Food enters the stomach from the esophagus.
- Mixing: The stomach muscles start churning, mixing food with the acidic gastric juices.
- Protein Breakdown: The enzyme pepsin, activated by the acid, begins protein digestion.
- Chyme Formation: This mixing and digestion process turns food into a semi-liquid mixture called chyme.
- Release to Duodenum: The chyme is then slowly released into the small intestine (duodenum) for further digestion and nutrient absorption.
Role of other organs in digestion
While the stomach is primarily responsible for the initial stages of digestion, other organs like the pancreas play a crucial role in later phases. The pancreas secretes digestive juice with enzymes for carbohydrates, fats and proteins, but these enzymes act in the small intestine, not the stomach.
