Migrating motor complex (MMC) phase III ('housekeeper wave') occurs during fasting. Which hormone triggers MMC phase III and which neural structure coordinates its propagation?
- A Secretin (released by S cells of duodenum) triggers phase III; the submucosal plexus coordinates propagation
- B Motilin (released by Mo cells of duodenum and proximal jejunum) triggers phase III; the myenteric plexus coordinates craniocaudal propagation ✓
- C Cholecystokinin (released by I cells) triggers phase III; the central vagal parasympathetic pathway coordinates propagation
- D VIP (vasoactive intestinal peptide from neurons) triggers phase III; the sympathetic nervous system coordinates propagation
Explanation
Motilin, a 22-amino-acid peptide secreted by Mo (EG) cells of the duodenum and proximal jejunum, rises cyclically every ~90–120 minutes during fasting to trigger MMC phase III (regular high-amplitude contractions that sweep from the stomach to the ileocaecal valve). The myenteric (Auerbach's) plexus coordinates the sequential, peristaltic propagation. MMC clears residual food, bacteria, and secretions ('intestinal housekeeper'). Erythromycin acts as a motilin receptor agonist, explaining its prokinetic use in gastroparesis. Ingestion of a meal immediately abolishes MMC activity.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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