The Bolus in Digestion: From Mouth to Elimination

A bolus is the semi-solid food-saliva mass formed by chewing. Its journey:

1. Mouth: Mechanical breakdown + salivary amylase starts carb digestion.
2. Esophagus: Peristalsis propels bolus to stomach.
3. Stomach: Gastric juices (HCl, pepsin) churn bolus into liquid chyme; protein digestion begins.
4. Small Intestine: Pancreatic enzymes (amylase, lipase, proteases) + bile emulsify fats; most nutrient absorption occurs.
5. Large Intestine: Water absorption; bacterial fermentation of fiber; stool formation.
6. Defecation: Waste elimination.

Throughout, the bolus transforms physically and chemically for nutrient extraction.