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 · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Arteries have a thick wall relative to their lumen diameter, which prevents them from bursting under the high pressure generated by the heart.
The tunica media contains a thick layer of smooth muscle; this muscle can contract or relax, thereby regulating the diameter of the artery and the flow of blood.
Elastic fibres (elastin) in the wall allow the artery to stretch during systole and recoil during diastole, which smooths out the pressure surges produced by each heartbeat.
Collagen fibres in the wall provide additional tensile strength, preventing the artery from over‑distending when peak systolic pressure occurs.

Examiner tips

  • Use the exact terms – thick wall, smooth muscle, elastin, collagen.
  • Show the function of each component – protection, regulation, elasticity, strength.
  • Keep the answer concise – one sentence per point.
  • Use correct UK spelling (e.g., ‘systole’, ‘diastole’).

Common mistakes

  • Confusing veins for arteries – arteries are the high‑pressure vessels. Using ‘muscle’ without specifying smooth muscle. Omitting the role of elastin or collagen in the wall’s mechanical properties.

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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