Which organ system transports nutrients, gases, and wastes throughout the body?

• A. The circulatory (cardiovascular) system
• B. The respiratory system
• C. The digestive system
• D. The lymphatic system

Answer: (B)

The circulatory system moves nutrients, gases, and wastes through the body. It consists of the heart, blood, and blood vessels, and it acts as the delivery network that keeps every cell stocked with what it needs. Nutrients absorbed from the digestive tract ride in the bloodstream to cells all over the body. Oxygen from the lungs is carried by red blood cells to tissues, while carbon dioxide and other wastes are collected from cells and returned to the lungs, liver, or kidneys for removal. The heart pumps blood through a branching system of vessels so this transport can reach every part of the body. While other systems play important roles—digestion provides nutrients, the respiratory system handles gas exchange, and the lymphatic system helps with immune function and fluid balance—the circulatory system is the main highway that moves nutrients, gases, and wastes to and from all cells.