Explain how the structure of arteries, capillaries and veins is related to their functions in the circulatory system.

Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 8 Grey Matter · Explain · 5 marks · View as Markdown

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

The circulatory system transports substances around the body using three types of blood vessel: arteries, capillaries and veins.

Model answer (5 marks)

Arteries carry blood away from the heart under high pressure. Their walls are thick and contain smooth muscle and elastic fibres, which allow them to withstand and maintain this pressure.
Capillaries are the site of exchange of substances between the blood and the tissues. Their walls are only one cell thick, which reduces the diffusion distance and allows rapid exchange.
Veins carry blood back to the heart at low pressure. Their walls are thinner than arteries and contain valves that prevent backflow of blood.

Examiner tips

  • Use the exact terms: 'thick walls', 'smooth muscle', 'elastic fibres', 'one cell thick', 'valves'
  • Show the link between structure and function for each vessel type

Common mistakes

  • Confusing arteries with veins in terms of pressure and wall thickness
  • Omitting the role of valves in veins
  • Not mentioning the thinness of capillary walls

Mark scheme (5 marks)

  1. Arteries carry blood away from the heart under high pressure
  2. Arteries have thick walls containing smooth muscle and elastic fibres to withstand / maintain high pressure
  3. Capillaries are the site of exchange of substances between the blood and the tissues
  4. Capillaries have thin walls (one cell thick) to reduce diffusion distance, allowing rapid exchange
  5. Veins carry blood back to the heart at low pressure and contain valves to prevent backflow of blood

Key terms in this question

capillaries · veins

Related

More Grey Matter questions

▶ Try answering this question with AI marking (free) →