Final answer:
The left ventricle has the highest pressure during isovolumetric contraction because it must generate enough force to pump blood into the systemic circuit, which has higher resistance than the pulmonary circuit.
Step-by-step explanation:
During isovolumetric contraction, the chamber with the greatest pressure is the left ventricle. This is because the left ventricle is the major pumping chamber for the systemic circuit, and it has to overcome high resistance to pump blood into the long systemic circuit. The muscle of the left ventricle is much thicker and better developed than that of the right ventricle, which allows the left ventricle to generate a greater amount of pressure. Although both ventricles pump the same amount of blood, the pressure generated by the left ventricle needs to be significantly higher to push blood into the aorta compared to the lower pressure needed by the right ventricle to pump blood into the shorter pulmonary circuit.