The main function of the lymphatic system is to transport lymph fluid throughout the body, which in turn helps with the functions of the immune system. The main parts of the lymphatic system are the lymph nodes, lymph vessels and lymph fluid, but the thymus, spleen, adenoids and tonsils are also considered part of the system.
The lymph system is also considered part of the circulatory system, as the lymph vessels also serve the function of transporting white blood cells back and forth between the lymph nodes and bones. White blood cells are one of the primary components of lymph fluid, along with chyle, a fluid produced by the intestines.
Along with transporting white blood cells, the lymph vessels also help to carry antigen-presenting cells to the lymph nodes. The nodes themselves produce cells that help to fight off infections while also filtering out the lymph fluid to get rid of bacteria and even cancerous cells.
When the lymph nodes detect bacteria in the fluid, they begin producing more white blood cells, which is why they often swell up when a person is ill. The nodes are present in many parts of the body, but the most prominent ones are in the groin, neck and armpits.