Describe the phases of gastric secretion, the mechanism by which NSAIDs cause gastric ulcers, and the mechanisms that prevent gastric autodigestion.

Here is the solution to your question: c) The phases of gastric secretion are: • Cephalic phase • Gastric phase • Intestinal phase D) NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) inhibit the production of prostaglandins in the stomach. Prostaglandins are crucial for maintaining the stomach's protective barrier by stimulating the secretion of mucus and bicarbonate, and promoting blood flow to the gastric mucosa. When prostaglandin production is reduced, this protective barrier weakens, making the stomach lining more vulnerable to damage from hydrochloric acid and pepsin, leading to inflammation and the formation of ulcers. E) Autodigestion of the stomach refers to the process where the stomach's own digestive enzymes (like pepsin) and strong acid (hydrochloric acid) begin to digest the stomach wall itself. This is prevented by several protective mechanisms: • The stomach lining is covered by a thick layer of alkaline mucus that neutralizes acid and protects the epithelial cells. • Bicarbonate ions are trapped within this mucus layer, creating a pH gradient that shields the stomach cells from the acidic lumen. • The epithelial cells are joined by tight junctions, preventing gastric juice from seeping between them. • Rapid regeneration of gastric epithelial cells ensures that damaged cells are quickly replaced. • The inactive form of the enzyme, pepsinogen, is secreted and only activated to pepsin in the acidic lumen, preventing intracellular digestion.