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The small intestine is the primary site where most nutrient molecules are absorbed in the human body. It is a long, coiled tube located between the stomach and the large intestine and is divided into three sections: the duodenum, jejunum, and ileum. After food is partially digested in the stomach, it moves into the small intestine, where enzymes and bile break it down into simple molecules such as amino acids, glucose, fatty acids, vitamins, and minerals.
The inner surface of the small intestine is lined with millions of villi and microvilli, which are tiny finger-like projections that increase the surface area for nutrient absorption. Each villus contains capillaries and lymph vessels that transport nutrients into the bloodstream or lymphatic system for distribution to the rest of the body.Key absorption functions of the small intestine:
Carbohydrates: Broken down into simple sugars like glucose and absorbed into the blood.
Proteins: Converted into amino acids and absorbed for tissue building and repair.
Fats: Broken into fatty acids and glycerol, absorbed via lymphatic vessels.
Vitamins and minerals: Essential micronutrients absorbed for overall body functioning.
Water and electrolytes: Also absorbed here, though some water is later absorbed in the large intestine.
Explanation of other options:
Stomach: Mainly performs digestion by acid and enzymes but very little nutrient absorption occurs except for alcohol and some drugs.
Liver: Processes and stores nutrients after absorption but does not directly absorb them from food.
Large intestine: Absorbs mainly water and electrolytes, not most nutrients.
None of these: Incorrect because the small intestine is the correct answer.
In conclusion, most nutrients from digested food are absorbed in the small intestine, making option A (Small intestine) the correct choice for this biology MCQ.
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