What is the primary function of the lymphatic system?

• A. To return interstitial fluid to the bloodstream and participate in immune defense
• B. To transport nutrients
• C. To remove carbon dioxide
• D. To regulate hormones

Answer: (A)

The main idea here is how the lymphatic system keeps the body’s fluid balance and defenses in check. Lymphatic vessels collect excess interstitial fluid that leaks out of capillaries and return it to the bloodstream, helping maintain blood volume and prevent tissue swelling. Lymph nodes and other immune tissues filter this lymph, trapping pathogens and enabling immune cells to respond, which is a central part of how the body defends itself.

This differs from transporting nutrients, which is the job of the digestive and circulatory systems; removing carbon dioxide, which is handled by the respiratory system; and regulating hormones, which is the role of the endocrine system. The lymphatic system does assist with absorbing fats from the digestive tract through special vessels, but its primary functions are fluid balance and immune defense.