What is the primary function of the lymphatic system?

The primary function of the lymphatic system is protection from infectious diseases. This system plays a crucial role in the body's immune response. It consists of a network of lymphatic vessels, lymph nodes, and lymphoid tissues, which work together to transport lymph – a fluid that contains immune cells, proteins, and various other substances.

When pathogens such as bacteria and viruses enter the body, lymphatic vessels help filter out these harmful invaders at the lymph nodes, where specialized immune cells, like lymphocytes, become activated to mount an immune response. This function is essential for maintaining the body's defense mechanisms and ensuring that infections are controlled and eliminated.

The other options describe functions that do not pertain specifically to the lymphatic system. Respiration is primarily associated with the respiratory system, while transportation of nutrients refers to functions carried out by the circulatory system and metabolism of carbohydrates is a function related to metabolic processes in various tissues, particularly in the digestive system and liver. Thus, while the lymphatic system may interact with these functions indirectly, its main role remains centered on providing protection against pathogens and supporting immune function.