The small intestine is the main site of nutrient absorption.

Question

BlackTom AI · Accepted Answer

The small intestine is the primary site of nutrient absorption because its structure and regional specialization are optimized for that role.

1) Relevant knowledge points and concepts
- Anatomy: the small intestine consists of the duodenum, jejunum, and ileum and is several meters long.
- Surface specialization: mucosal folds, villi, and microvilli (brush border) enormously increase surface area for absorption.
- Function: enzymatic digestion and absorption of carbohydrates, proteins (as amino acids), lipids (as fatty acids and monoglycerides), vitamins, minerals, and most water-soluble nutrients.
- Regional roles: duodenum receives bile and pancreatic enzymes and absorbs iron and calcium; jejunum is the major site for most nutrient absorption; ileum absorbs bile salts and vitamin B12.

2) Step-by-step reasoning
- Food is broken down mechanically and chemically in the stomach, but macronutrient digestion continues and is completed in the small intestine with pancreatic enzymes and bile acting in the duodenum.
- The chyme contacts the mucosal surface of the small intestine, where villi and microvilli provide an extensive absorptive surface permitting rapid transfer of digested molecules into blood or lymph.
- Transport mechanisms (active transport, facilitated diffusion, simple diffusion) move glucose, amino acids, fatty acids, vitamins, and minerals across enterocytes into circulation.
- The large intestine’s main roles are water and electrolyte absorption and fermentation of remaining material by gut microbes; it does not absorb the majority of nutrients.

3) Calculations
- No numeric calculation is required here; the conclusion follows from anatomical and physiological evidence.

4) Why the correct answer is correct
- Given the anatomy (long tube with specialized absorptive epithelium) and physiology (site of enzymatic digestion completion and uptake of macronutrients, micronutrients, and many vitamins), the small intestine is clearly the main site of nutrient absorption.

5) Why the other option is incorrect
- “False” would imply nutrients are primarily absorbed elsewhere (e.g., stomach or large intestine), which is incorrect because the stomach mainly digests and the large intestine primarily absorbs water/electrolytes and some vitamins, not the bulk of nutrients.

6) Conclusion
- Therefore, the correct answer is True, which matches the provided answer.

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

类似问题

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Question at position 39 How do nutrients from food actually enter the body’s tissues?By mechanical digestion in the stomachBy filtration through the kidneysThrough absorption in the digestive tractThrough enzymatic breakdown in the esophagus

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