Review Questions
1. Which of these cells secrete hormones?
2. Where does the majority of chemical digestion in the stomach occur?
3. During gastric emptying, chyme is released into the duodenum through the ________.
4. Parietal cells secrete ________.
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1. Explain how the stomach is protected from self-digestion and why this is necessary.
Solution: The mucosal barrier protects the stomach from self-digestion. It includes a thick coating of bicarbonate-rich mucus; the mucus is physically protective, and bicarbonate neutralizes gastric acid. Epithelial cells meet at tight junctions, which block gastric juice from penetrating the underlying tissue layers, and stem cells quickly replace sloughed off epithelial mucosal cells.
2. Describe unique anatomical features that enable the stomach to perform digestive functions.
Solution: The stomach has an additional inner oblique smooth muscle layer that helps the muscularis churn and mix food. The epithelium includes gastric glands that secrete gastric fluid. The gastric fluid consists mainly of mucous, HCl, and the enzyme pepsin released as pepsinogen.
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