What is the primary function of the lymphatic system?

The primary function of the lymphatic system is to transport lymph, filter pathogens, and facilitate immune cell circulation. The lymphatic system plays a crucial role in maintaining fluid balance in the body by collecting excess interstitial fluid and returning it to the bloodstream. Additionally, it is integral to the immune system; lymph nodes, which are distributed throughout the lymphatic network, act as filters that trap pathogens, while lymph carries immune cells such as lymphocytes throughout the body. This circulation of immune cells is essential for the immune response, allowing the body to detect and respond to infections and other threats effectively.

The other options pertain to functions of different systems: hormones that regulate metabolism are primarily produced by the endocrine system; nutrient absorption from digested food is mainly the role of the digestive system; while the circulation of oxygen and nutrients is primarily the responsibility of the cardiovascular system. Each option highlights distinct physiological processes that do not align with the primary functions of the lymphatic system.