Systemic circulation refers to blood flow between which regions?

• A. The heart and the body tissues (excluding the lungs)
• B. The heart and the lungs
• C. The brain and spinal cord
• D. The arteries and veins

Answer: (A)

Systemic circulation describes the pathway of blood moving between the heart and the body’s tissues, excluding the lungs. After the left ventricle pumps into the aorta, oxygen-rich blood travels through systemic arteries to capillaries in body tissues, where it delivers oxygen and nutrients and picks up carbon dioxide and wastes, then returns to the heart through systemic veins into the right atrium. The lungs aren’t part of this loop; the blood–lung pathway is a separate circuit called pulmonary circulation. So the description that matches blood flow between the heart and the body tissues (excluding the lungs) fits systemic circulation best. The other options don’t define the circulating loop: pulmonary circulation involves the heart and lungs, while vessels alone don’t specify the tissue-exchange pathway.