# Explain how the structure of an artery is adapted to withstand and regulate the high-pressure flow of blood away from the heart.

> IB DP Biology Standard Level (2023 syllabus) — B3.2 Transport · Explain · 4 marks

## Mark scheme (4 marks)

1. Arteries have a thick wall (relative to their lumen diameter) to withstand high blood pressure without bursting.
2. A thick layer of smooth muscle in the tunica media allows the artery to contract or relax, regulating blood flow and pressure.
3. Elastic fibres (elastin) in the wall allow the artery to stretch during systole and recoil during diastole, smoothing out pressure surges.
4. Collagen fibres in the wall provide tensile strength, preventing over-distension of the artery under peak systolic pressure.

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