Which circuit carries oxygen-rich blood to all body organs and then returns oxygen-poor blood to the right atrium?

• A. Systemic Circuit
• B. Pulmonary Circuit
• C. Coronary Arteries
• D. Cardiac Veins

Answer: (A)

Systemic circulation is the movement of oxygen-rich blood from the left side of the heart to all body tissues, where oxygen is delivered and waste gases are picked up, and then back to the right atrium as oxygen-poor blood. Blood leaves the left ventricle through the aorta and travels via systemic arteries to capillaries throughout the body. After delivering oxygen and nutrients, the blood returns through veins, ultimately draining into the superior and inferior vena cava (and the coronary veins into the coronary sinus), which empty into the right atrium. This loop supplies all organs with oxygenated blood and recovers deoxygenated blood to be sent to the lungs by the pulmonary circuit.

The pulmonary circuit, by comparison, handles blood moving between the heart and the lungs for gas exchange, while the coronary arteries and veins supply and drain the heart muscle itself but don’t serve the entire body’s circulation.