Which body system transports oxygen and nutrients and removes waste most efficiently?

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

Answer: (D)

Transport of oxygen, nutrients, and waste relies on a system that keeps blood flowing to every cell. The circulatory system, made up of the heart, blood vessels, and blood, does this by pumping blood that carries oxygen from the lungs and nutrients from the digestive tract to all tissues, and carries carbon dioxide and other wastes back to the lungs, liver, and kidneys for elimination. The other systems have important roles but don’t perform this broad transport function: the nervous system transmits signals and doesn’t move substances around the body; the lymphatic system helps with immune responses and fluid balance but isn’t the main highway for nutrient and oxygen delivery or waste removal; the respiratory system handles gas exchange, bringing in oxygen and expelling carbon dioxide, but it relies on the circulatory system to deliver that oxygen to cells throughout the body. Because it coordinates the movement of essential substances and the removal of wastes across all tissues, the circulatory system does this most efficiently.