The primary functions of the lymphatic system include?

• A. Filters air in the lungs
• B. Defends against infection and returns tissue fluids to the bloodstream
• C. Produces red blood cells
• D. Stores minerals

Answer: (B)

Understanding how the lymphatic system maintains fluid balance and protects the body helps explain why these are its primary roles. It collects excess fluid that leaks from capillaries into tissues (which becomes lymph) and returns it to the bloodstream, helping maintain blood volume and tissue fluid balance. It also houses immune cells in lymph nodes and other organs, providing surveillance and defense against infections. Lymph flow through this network is filtered by nodes where pathogens are detected and immune responses can be activated. These two functions—returning tissue fluid to the bloodstream and defending against infection—best describe the main jobs of the lymphatic system. The other options point to the respiratory system, the site of red blood cell production, and mineral storage in bones, which are not primary lymphatic roles.