Educational worksheet illustrating the structure of a villus and its role in nutrient absorption in the small intestine.

Let's solve the problem step by step based on the image you've described. The task is about absorption in the small intestine, focusing on the structure and function of villi.

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1) Label the Villus

We are given a diagram of a villus with four labeled parts (1 to 4), and we need to identify them using these terms:
- Blood capillary
- Lacteal (lymph vessel)
- Intestine wall
- Microvilli

Here’s how to label each part:

#### Diagram Interpretation:
- The outer surface of the villus (the lining of the intestine) has tiny finger-like projections called microvilli.
- Inside the villus, there is a network of blood capillaries (red lines) that absorb glucose, amino acids, and glycerol.
- There is also a lacteal (yellow or blue line), which is a lymphatic vessel that absorbs fatty acids and glycerol.
- The intestine wall refers to the outer layer of the intestinal lining, which contains the villi.

Now, let’s match the numbers:

1. Microvilli – These are the tiny projections on the surface of the epithelial cells (the "brush border"). They increase surface area for absorption.
2. Intestine wall – This is the outer layer surrounding the lumen (the inner space where digested food is).
3. Lacteal (lymph vessel) – The central yellow/blue tube inside the villus that absorbs fats.
4. Blood capillary – The red network around the lacteal that absorbs sugars and amino acids.

✔ So, the labels are:

| Number | Label |
|--------|-------|
| 1 | Microvilli |
| 2 | Intestine wall |
| 3 | Lacteal (lymph vessel) |
| 4 | Blood capillary |

> ⚠️ Note: In some diagrams, the numbering may vary slightly depending on layout, but based on standard biology diagrams:
> - 1 → Microvilli (surface projections)
> - 2 → Intestine wall (outer layer)
> - 3 → Lacteal (central lymph vessel)
> - 4 → Blood capillary (surrounding the lacteal)

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2) Complete the Table: How Do Villi Speed Up Absorption?

We are to complete the table explaining how each feature of the villus helps absorption.

| Feature of villus | How the feature helps speed up absorption |
|-------------------|--------------------------------------------|
| Lining of intestine only one cell thick | Allows rapid diffusion of nutrients directly into the blood/lacteal because there is no barrier. |
| Good blood supply | Maintains concentration gradient; continuously removes absorbed substances, allowing more to diffuse in. |
| Presence of lacteal (lymph vessel) | Absorbs fatty acids and glycerol (products of fat digestion), which cannot enter blood capillaries easily. |
| Microvilli | Increase surface area dramatically, allowing more efficient absorption of nutrients. |

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✔ Final Answer Summary:

#### Part 1: Label the Villus
1. Microvilli
2. Intestine wall
3. Lacteal (lymph vessel)
4. Blood capillary

#### Part 2: Table Completion

| Feature of villus | How the feature helps speed up absorption |
|-------------------|--------------------------------------------|
| Lining of intestine only one cell thick | Enables fast diffusion as nutrients pass through just one cell layer. |
| Good blood supply | Helps maintain concentration gradient, promoting continuous absorption. |
| Presence of lacteal (lymph vessel) | Transports fatty acids and glycerol into the lymphatic system. |
| Microvilli | Greatly increase surface area for absorption. |

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🔍 Explanation:

- Villi are finger-like projections in the small intestine that increase the surface area for absorption.
- Microvilli are even smaller projections on the surface of the epithelial cells, forming the brush border.
- The blood capillaries absorb water-soluble nutrients like glucose and amino acids.
- The lacteal absorbs fat-soluble products (fatty acids and glycerol), which are transported via lymph before entering the bloodstream.
- The thin epithelium allows quick diffusion.
- The rich blood supply ensures that absorbed materials are quickly removed, maintaining a steep concentration gradient.

This structure makes the small intestine highly efficient at absorbing nutrients from digested food.

Let me know if you'd like a visual sketch explanation or further details!