English worksheets: Blood Vessels - a comparison - Free Printable

It looks like you've uploaded an image of a worksheet titled "Blood Vessels – a summary", which is designed to help students understand the structure and function of different types of blood vessels (arteries, capillaries, and veins). However, since I can't view images directly, I’ll guide you through how to complete this worksheet based on typical biology content.

Let’s go step by step and fill in the table and diagrams as they would be expected in a standard biology curriculum.

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🔹 Part 1: Table – Blood Vessels Summary

| Structure | Arteries | Capillaries | Veins |
|---------------|--------------|------------------|-----------|
| Think layer of muscle, smooth muscle | Thick | Thin or none | Thin |
| Exchange of wastes or gases | No | Yes | No |
| Wall thickness | Thick | Very thin | Thin |
| Lumen size | Small | Very small | Large |
| Direction of blood flow | From heart → body | Body ↔ heart | Body → heart |
| Presence of valves | None | None | Yes (in many) |
| Pressure | High | Low | Low |

> ✔ Explanation:
> - Arteries carry blood away from the heart under high pressure. They have thick muscular walls to withstand pressure.
> - Capillaries are tiny vessels where gas and nutrient exchange occurs. Their walls are one cell thick for efficient diffusion.
> - Veins return blood to the heart under low pressure. They have thinner walls and often contain valves to prevent backflow.

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🔹 Part 2: Diagrams – Cross-Section of Blood Vessels

You’re likely given three cross-sectional diagrams labeled:
1. A – Artery
2. B – Capillary
3. C – Vein

#### Identify the parts:
- Label the layers:
- Tunica intima – innermost layer (endothelium)
- Tunica media – middle layer (smooth muscle and elastic fibers)
- Tunica externa – outer layer (connective tissue)

#### Match each diagram:

| Diagram | Vessel Type | Key Features |
|--------|-------------|------------|
| A | Artery | Thick tunica media, no valves, narrow lumen |
| B | Capillary | Only tunica intima (one cell thick), very narrow lumen |
| C | Vein | Thinner wall than artery, larger lumen, may have valves |

> 💡 Tip: Arteries have thicker walls than veins, while veins have flatter muscles and sometimes valves.

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🔹 Part 3: Fill-in-the-blank Questions

Below the table, there might be statements like:

> "The vessel that carries blood from the heart to the body is called a(n) ______."

✔ Answer: Artery

> "The vessel where exchange of gases and nutrients occurs is the ______."

✔ Answer: Capillary

> "The vessel that returns blood to the heart has valves to prevent backflow — this is a(n) ______."

✔ Answer: Vein

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🔹 Final Tips for Completing the Worksheet

1. Compare structures:
- Arteries: thick walls, no valves, high pressure
- Capillaries: thin walls, site of exchange
- Veins: thin walls, valves, low pressure

2. Use keywords:
- Diffusion happens in capillaries.
- Muscle in arteries helps maintain pressure.
- Valves in veins prevent backflow.

3. Draw clearly:
- Label the layers in the diagrams.
- Show that capillaries are much thinner than arteries/veins.

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