The Stomach's Digestive Functions: Storage, Mechanical & Chemical Breakdown, and Controlled Emptying

Key Roles

1. Reservoir: Accommodates ingested volume via receptive relaxation.
2. Mechanical digestion: Vigorous peristaltic churning reduces particle size.
3. Chemical digestion: Parietal cells secrete HCl; chief cells secrete pepsinogen → pepsin (protein hydrolysis). Acid also sterilizes.
4. Mixing & propulsion: Chyme formation; pyloric metering into duodenum.
5. Limited absorption: Water, alcohol, certain drugs (e.g., aspirin).

Gastric emptying is tightly regulated by neural/hormonal feedback (CCK, secretin, gastrin).