Which system is responsible for removing carbon dioxide from the bloodstream?

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

Answer: (A)

Gas exchange in the lungs handles removal of carbon dioxide from the bloodstream. As cells produce CO2, it travels in the blood, largely as bicarbonate, to the lungs. There, CO2 diffuses from the blood into the alveoli and is expelled when you exhale. This ventilation-diffusion process is the body's primary way to eliminate CO2. The excretory system deals with wastes filtered by the kidneys and urine, the endocrine system governs hormones, and the lymphatic system supports immune function and fluid balance—none are primarily responsible for gas exchange.