Which system circulates blood, oxygen, hormones, toxins, and lymph through the body?

• A. Circulatory System
• B. Nervous System
• C. Digestive System
• D. Endocrine System

Answer: (A)

The circulatory system is responsible for moving blood and everything it carries—oxygen, hormones, wastes, and related substances—throughout the body. It includes the heart as the pump and a network of arteries, veins, and capillaries that deliver oxygen from the lungs to cells and carry carbon dioxide and other wastes away for elimination. Hormones produced by endocrine glands ride in the bloodstream to reach their target organs, while toxins and other materials are transported to organs like the liver and kidneys for processing and removal. Lymphatic fluid interacts with this system to maintain fluid balance and support immune function, but the driving transport of blood and its cargo is the circulatory system. The nervous, digestive, and endocrine systems don’t perform this broad transport role in the same way.