State the main function of veins in human circulatory system. Why do they not need thick walls ?
Generated by claude-sonnet-4-6 · 2026-06-11 09:51 · grounding rag
Model Answer
Function of veins: Veins collect deoxygenated blood from different organs and bring it back to the heart.
Why no thick walls: The blood in veins is no longer under high pressure (unlike arteries), so thick elastic walls are not needed. Instead, veins have valves to ensure blood flows only in one direction toward the heart.
Source: Chapter 5, Section 5.4.1 – The tubes – blood vessels
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Explanation
- Two points are expected: (1) function of veins and (2) reason for thin walls — each worth 1 mark.
- Key phrase examiners look for: "blood is no longer under pressure" + mention of valves (this distinguishes veins from arteries structurally).
- Don't confuse: arteries carry blood away from heart under high pressure → thick walls; veins carry blood back to heart under low pressure → thin walls + valves.