Which feature of a villus is NOT an adaptation for absorption?
Correct answer: D. A thick covering of muscle around each villus
- A. A dense network of blood capillaries
- B. A single layer of epithelial cells covering it
- C. Microvilli on the free surface of its cells
- D. A thick covering of muscle around each villus
Explanation
A villus is adapted by being thin walled, richly supplied with blood and lymph and covered in microvilli, all of which shorten the diffusion path or enlarge the surface. A thick muscular coat would do the opposite by lengthening the distance nutrients must travel. Muscle lies in the wall of the intestine as a whole, where it produces peristalsis, not around individual villi.
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About Human Digestive System
The human digestive system breaks food into absorbable molecules through mechanical processing, enzyme action and chemical conditions along the alimentary canal. Questions cover the mouth, stomach, small and large intestines, liver, pancreas and associated secretions, including the digestion and absorption of carbohydrates, proteins, lipids, vitamins, minerals and water.
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