Final answer:
The left ventricle has thicker walls to generate higher pressure for efficient blood circulation in the long systemic circuit. This ensures a) oxygen, b) nutrients, and other substances reach all parts of the body.
Step-by-step explanation:
The left ventricle has thicker walls because it needs to generate a greater amount of pressure to pump blood into the long systemic circuit. This is necessary to overcome the high resistance and ensure that blood reaches all parts of the body. On the other hand, the right ventricle does not need to generate as much pressure because the pulmonary circuit is shorter and provides less resistance.
Figure 19.8 illustrates the differences in muscular thickness between the left and right ventricles. The left ventricle is much thicker and better developed to handle the greater pressure required for systemic circulation. The thicker walls of the left ventricle allow for efficient propulsion of oxygen, nutrients, and other substances to all the organs and tissues in the body.