The large intestine is the main site of nutrient absorption.

Question

BlackTom AI · Accepted Answer

Nutrient absorption primarily occurs in the small intestine, not the large intestine.

1) Relevant knowledge points and concepts:
- The gastrointestinal tract is specialized: the small intestine (duodenum, jejunum, ileum) is the principal absorptive organ for nutrients (carbohydrates, proteins, fats, vitamins, minerals).
- Structural adaptations in the small intestine—villi and microvilli (the brush border)—vastly increase surface area and contain transporters and enzymes for nutrient uptake.
- The large intestine (colon) specializes in absorbing water and electrolytes, fermenting indigestible fiber via gut microbiota into short-chain fatty acids (SCFAs), and synthesizing certain vitamins (vitamin K, some B vitamins) that can be partially absorbed. It lacks villi and has a different epithelial structure (crypts), so its capacity for macronutrient absorption is limited.

2) Step-by-step reasoning:
- Step 1: Identify where macronutrients are broken down: digestion of starches, proteins, and fats is completed in the small intestine with pancreatic enzymes and bile acting in the duodenum and jejunum.
- Step 2: Recognize absorption mechanisms: monosaccharides, amino acids, dipeptides, fatty acids, glycerol are taken up across enterocytes of the small intestine via specific transporters and enter the bloodstream or lymphatic lacteals.
- Step 3: Compare structure/function: small intestine’s villi/microvilli provide high surface area; colon lacks these, so cannot match its absorptive capacity for nutrients.
- Step 4: Note exceptions: the colon absorbs water, electrolytes, SCFAs from bacterial fermentation, and some vitamins—these are not the major nutrient absorptions such as carbs, proteins, fats.

3) Calculations: none needed.

4) Why the correct answer is correct:
Because the small intestine is anatomically and functionally specialized for absorbing the bulk of nutrients, the statement that “The large intestine is the main site of nutrient absorption” is false.

5) Why the other option is incorrect:
Choosing “True” would ignore the structural and functional evidence that the small intestine performs the majority of nutrient absorption; the colon’s role is mainly water/electrolyte recovery and processing of residual material.

Conclusion: The correct answer is False, matching the provided answer.

The large intestine is the main site of nutrient absorption.判断题

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