Explain why the left ventricle of the heart has a thicker wall than the right ventricle, and describe the role of the atrioventricular valves in ensuring blood flows in the correct direction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
The left ventricle pumps blood to the entire body (systemic circulation) and therefore must generate a higher blood pressure than the right ventricle, which only supplies the lungs. A thicker wall gives the left ventricle a more powerful contraction, allowing it to produce the required high pressure.
The atrioventricular valves lie between the atria and the ventricles. They close when the ventricles contract, preventing backflow of blood from the ventricles into the atria and ensuring unidirectional flow.
The atrioventricular valves lie between the atria and the ventricles. They close when the ventricles contract, preventing backflow of blood from the ventricles into the atria and ensuring unidirectional flow.
Examiner tips
- Use the term ‘systemic circulation’ for the left ventricle’s role.
- Explain that higher pressure requires a thicker wall for stronger contraction.
- Mention the valves’ position and their function of preventing backflow.
Common mistakes
- Confusing the right ventricle with the left in terms of pressure requirements.
- Failing to state the valves’ location between atria and ventricles.
- Overlooking the back‑flow prevention function of the AV valves.
Mark scheme (5 marks)
- The left ventricle pumps blood around the entire/whole body (systemic circulation)
- The left ventricle must generate a higher/greater blood pressure than the right ventricle
- A thicker wall means a more powerful contraction (to generate this high pressure)
- The atrioventricular valves are located between the atria and the ventricles
- The atrioventricular valves prevent backflow of blood from the ventricles into the atria
Key terms in this question
left ventricle · atrioventricular valves
Related
- All WJEC A-Level Biology (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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