As blood travels from arteries to veins,

Options

A. pressure builds.
B. pressure drops.
C. flow becomes turbulent.
D. diameter of the blood vessels gets progressively smaller.

Answer

**Step-by-Step Solution:**

1. **Understanding Blood Flow:** Blood circulates through the body in a closed system, moving from the heart to the arteries, then to the capillaries, and finally returning to the heart via the veins.

2. **Arteries to Capillaries:** Blood is pumped from the heart into the arteries. The arteries have thick walls and a narrow lumen, which helps maintain high blood pressure. As blood moves into smaller arteries and arterioles, it eventually reaches the capillaries.

3. **Capillary Exchange:** Capillaries are tiny blood vessels where the exchange of gases, nutrients, and waste occurs. The blood pressure in capillaries is lower than in arteries, allowing for this exchange.

4. **Transition to Veins:** After passing through the capillaries, blood enters the veins. The veins have a larger lumen compared to arteries, which contributes to a decrease in blood pressure as blood returns to the heart.

5. **Pressure Changes:** As blood moves from arteries to veins, the pressure decreases significantly. This is due to the increased cross-sectional area of the vascular system as blood transitions from the narrow arteries to the wider veins.

6. **Flow Characteristics:** The flow of blood becomes less turbulent as it moves from the high-pressure arteries to the lower-pressure veins. The blood flow is more streamlined in veins due to their larger diameter.

7. **Conclusion:** Therefore, as blood travels from arteries to veins, the pressure drops, the flow becomes less turbulent, and the diameter of the blood vessels increases.

**Final Answer:** As blood travels from arteries to veins, the pressure drops.

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