Cardiac muscle consists of numerous fibres that make up the walls of the heart chambers. As the heart contracts, these fibres become shorter, so the muscle produces a force that applies pressure to the blood and makes it flow. Which statement explains why the walls of the ventricles of the heart are different in thickness?
- AThere is more muscle in the wall of the right ventricle than that of the left ventricle because more pressure is needed to push blood into the aorta than into the pulmonary artery.
- BThe number of muscle fibres in the left ventricle is greater than the number in the right ventricle so their contraction has more force, exerting more pressure on blood.
- CThe space available to fill with blood inside the left ventricle is smaller than that of the right ventricle so more pressure is needed to force blood out.
- DThe wall of the right ventricle is thicker than that of the left ventricle because it has to resist more pressure when the muscle of the right ventricle contracts.