What are capillaries?

Explanation

**Step-by-Step Solution:**

1. **Definition of Capillaries**: Capillaries are very small and thin blood vessels in the body. They are the smallest type of blood vessels, connecting arteries and veins.

2. **Structure of Capillaries**: Capillaries have thin walls, which is crucial for their function. The thinness of these walls allows for easy exchange of substances.

3. **Function of Capillaries**: The primary function of capillaries is to facilitate the exchange of oxygen, nutrients, carbon dioxide, and waste products between the blood and the tissues of the body.

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