Two functions of mucus produced by duodenal submucosal glands when chyme arrives from the stomach?

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When acidic chyme arrives in the duodenum, the body needs to protect the lining and create a suitable environment for digestion. The mucus secreted by the duodenal submucosal glands (Brunner’s glands) is alkaline and rich in bicarbonate. This alkaline mucus forms a protective buffer layer on the mucosa and neutralizes much of the stomach acid, raising the pH of the chyme as it reaches the small intestine. This dual action—shielding the epithelium and adjusting pH—prepares the intestinal surface for enzyme activity and protects against acid injury.

Lubrication is a secondary role of mucus, but transporting chyme or digesting it with enzymes isn’t a function of these glands. Enzymatic digestion is carried out by other secretions (like pancreatic enzymes and intestinal enzymes), and villus motility is regulated by neural and hormonal signals rather than mucus secretion.