Final answer:
The left ventricle is responsible for pumping oxygenated blood into the aorta, which then distributes it throughout the body's systemic circuit.
Step-by-step explanation:
The region of the heart that supplies oxygenated blood to the aorta is the left ventricle. After blood becomes oxygen-rich in the lungs, it is transported to the left atrium and then to the left ventricle through the bicuspid valve. The left ventricle then pumps the oxygenated blood into the aorta, thereby supplying the systemic circuit with the oxygen necessary for cellular functions.