Explain why the walls of arteries are thicker and more muscular than the walls of veins.

Pearson Edexcel International GCSE Biology (4BI1) — 2.11 Transport: humans · Explain · 4 marks · View as Markdown

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

Blood is transported around the body through a network of blood vessels. Arteries carry blood away from the heart, whilst veins carry blood back towards the heart.

Model answer (4 marks)

Arteries carry blood away from the heart and therefore the blood inside them is at a higher pressure than in veins. The walls of arteries are therefore thicker and contain more smooth muscle so that they can withstand and resist the high pressure and prevent bursting. In contrast, veins return blood to the heart and the pressure inside them is lower, so their walls can be thinner and still be strong enough to carry the blood back.

Examiner tips

  • Mention the higher pressure in arteries and the need for thicker, muscular walls to resist it
  • Explain that veins have lower pressure so thinner walls are adequate
  • Use the terms 'arteries', 'veins', 'pressure', 'muscular walls'
  • Keep the answer concise and directly linked to the marks

Common mistakes

  • Confusing the direction of blood flow with pressure differences
  • Using vague terms like 'stronger' without specifying pressure
  • Including irrelevant details such as valves or oxygen content

Mark scheme (4 marks)

  1. Blood in arteries is at higher pressure (than in veins)
  2. Thick muscular walls withstand / prevent bursting due to the high pressure
  3. Blood in veins is at lower pressure (than in arteries)
  4. Thinner walls are sufficient because veins do not need to withstand high pressure

Key terms in this question

arteries · veins

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