Small Intestine

Where absorption happens

How does the small Intestine work?

About 6 meters long. Its lining folds into millions of villi, multiplying the surface area for absorbing nutrients.

Three parts

Duodenum (enzymes and bile arrive), jejunum (most absorption), ileum (B12 and bile salts reabsorbed).

Different paths

Sugars, amino acids and minerals enter blood and go to the liver first. Most fats enter lymph vessels.

Evidence & sources

• Most digestion and nutrient absorption happen in the small intestine. Evidence: established. Known: Basic digestive physiology. Unknown: — Source: NIH NIDDK, Your Digestive System & How It Works (Current revision).

Connected topics

• Digestive System
• Protein
• Carbohydrate
• Fat
• Iron
• Calcium
• Potassium
• Vitamin B12
• Blood

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General education only, not medical advice. Drafted Oct 2026 · pending qualified expert review.