What is the circulatory system?

• A. The system that filters toxins from the blood
• B. The system that produces hormones
• C. The system that exchanges gases in the lungs
• D. The system that controls the steady movement of blood through the body

Answer: (D)

The circulatory system is the network that keeps blood moving through the body in a continuous loop, with the heart acting as the pump and blood vessels forming the transit pathways. Its main job is to ensure a steady flow so every tissue receives oxygen and nutrients and wastes are carried away, maintaining perfusion and blood pressure. That’s why describing it as the system that controls the steady movement of blood through the body is the best fit. Other options point to other body systems: filtering toxins is done mainly by the liver and kidneys, gas exchange occurs in the lungs as part of the respiratory system, and hormone production is a function of the endocrine system.