Where does the systemic circuit begin and end?

• A. Begins at left ventricle, ends at right atrium
• B. Begins at right atrium, ends at left ventricle
• C. Begins at left atrium, ends at right ventricle
• D. Begins at right ventricle, ends at left atrium

Answer: (A)

The systemic circuit is the pathway that carries oxygen-rich blood from the heart out to the body and back as oxygen-poor blood. It begins when the left ventricle ejects blood into the aorta, which then distributes throughout the body via arteries and capillaries, and returns to the heart through systemic veins into the right atrium (via the superior and inferior vena cavae and the coronary sinus). This setup contrasts with the pulmonary circuit, which starts at the right ventricle and ends at the left atrium as blood is sent to the lungs for gas exchange.