Which system works with the circulatory system to deliver oxygen to tissues?

• A. Respiratory System
• B. Circulatory System
• C. Endocrine System
• D. Lymphatic System

Answer: (A)

Gas exchange and oxygen delivery involve the respiratory and circulatory systems working together. The respiratory system brings in oxygen and releases carbon dioxide; oxygen moves from the air into the blood in the lungs and binds to hemoglobin. The circulatory system then pumps this oxygen-rich blood to tissues throughout the body. Without the respiratory system providing the oxygen, the blood couldn’t deliver it to tissues—so the respiratory system is the partner system that makes oxygen delivery possible. The endocrine system and lymphatic system don’t directly handle oxygen supply to tissues.