PATHOLOGY

Detailed explanation-1: -Oxygen-deficient, carbon dioxide-rich blood returns to the right side of the heart through two large veins, the superior vena cava and the inferior vena cava. Then the blood is pumped through the pulmonary artery to the lungs, where it picks up oxygen and releases carbon dioxide.

Detailed explanation-2: -The organ system that maintains blood oxygen and carbon dioxide levels is the respiratory system. This system primarily revolves around the lungs, the major organs where gas exchange occurs.