The function of the lymphatic system in the human body is to maintain fluid balance and support the immune system. It collects and returns excess interstitial fluid to the bloodstream, preventing edema. The lymphatic system also transports lymph, a fluid that contains white blood cells, playing a vital role in the body's defense against pathogens. Additionally, lymph nodes filter lymph fluid, trapping bacteria and other harmful substances, thereby contributing to the overall health and protection of the organism.