Which organ system is responsible for transporting blood and nutrients?

• A. Digestive system
• B. Circulatory system
• C. Nervous system
• D. Respiratory system

Answer: (D)

Transport of blood and nutrients is the job of the circulatory system. The heart acts as a pump that pushes blood through a vast network of vessels—arteries, capillaries, and veins—so nutrients absorbed from the digestive tract can be carried to every cell, while waste products and gases are transported to where they’re processed or excreted. The digestive system does the work of breaking down food and extracting nutrients, but it’s the circulatory system that distributes those nutrients throughout the body. The respiratory system handles gas exchange (oxygen in, carbon dioxide out), and the nervous system coordinates responses and signals, but neither is primarily responsible for moving blood and nutrients around. So the circulatory system is the correct choice.