Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.

Cambridge International IGCSE Biology (0610) — 9.1 Circulatory systems · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

The left ventricle pumps blood to the whole body, so it must generate a higher blood pressure. The right ventricle only pumps blood to the lungs, requiring less pressure. A thicker muscular wall in the left ventricle contracts more powerfully, producing the greater force needed for systemic circulation.

Examiner tips

Use the exact terms ‘left ventricle’, ‘right ventricle’, ‘higher blood pressure’, ‘thicker wall’, ‘more force’.
Show the cause–effect link: systemic vs pulmonary circulation → pressure difference → wall thickness.
Keep the answer concise – 4 marks can be earned with 4 short sentences.

Common mistakes

Confusing the direction of blood flow (e.g., saying the right ventricle pumps to the body).
Using vague terms like ‘stronger’ without linking to pressure or wall thickness.
Leaving out the reason the left ventricle needs higher pressure.

Mark scheme (4 marks)

The left ventricle pumps blood to the whole body / around the entire body
The right ventricle pumps blood only to the lungs
The left ventricle must generate a higher / greater blood pressure
A thicker muscular wall contracts more powerfully / produces more force to achieve this higher pressure

Key terms in this question

ventricle · left ventricle · right ventricle