Final answer:
The myocardium in the left ventricle is thicker than that of the right ventricle because the left ventricle needs to generate greater pressure to overcome higher resistance in the systemic circuit.
Step-by-step explanation:
The myocardium in the left ventricle is significantly thicker than that of the right ventricle. Both ventricles pump the same amount of blood, but the left ventricle must generate a much greater pressure to overcome greater resistance in the systemic circuit. This is illustrated in Figure 19.8, which shows the differences in muscular thickness between the ventricles. The left ventricle is thicker because it needs to pump blood into the longer systemic circuit with higher resistance.