Explain how the structure of a villus helps absorption of digested food in the small intestine.
🍽️ 7.2 Human Nutrition – Alimentary Canal
How the Structure of a Villus Helps Absorption
A villus is a tiny, finger‑like projection that lines the inside of the small intestine. Think of it as a micro‑market where food is sold to the body. The more surface area it has, the faster the body can “buy” the nutrients.
- Large surface area: ~2000 m² in the whole intestine.
- Microvilli on epithelial cells form the brush border, increasing area even more.
- Rich blood supply and lymphatic vessels (lacteals) pick up nutrients.
Analogy: The Villus as a Sponge 🧽
Imagine a sponge soaking up water. The villus, with its tiny pores (microvilli), soaks up sugars, amino acids, and fatty acids from the digested food.
Key Points for the Exam
- Explain the role of microvilli in increasing surface area.
- Describe how blood vessels and lacteals transport absorbed nutrients.
- Use the equation for surface area of a cylinder: $A = 2\pi r h + 2\pi r^2$ to show why many villi are beneficial.
- Give an example of a nutrient absorbed via the villus.
Exam Tip Box 📝
Tip: When answering, start with the structure (villus shape, microvilli, blood vessels), then explain the function (absorption), and finish with an example. Use diagrams if allowed.
| Feature | Function |
|---|---|
| Villus | Increases surface area for absorption. |
| Microvilli | Brush border; further increases area. |
| Blood vessels | Transport nutrients to bloodstream. |
| Lacteals | Absorb fatty acids into lymph. |
Revision
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