The lymphatic system helps fight infection and disease. It is composed of lymph vessels that carry lymph fluid containing white blood cells. Lymph fluid is similar to plasma but contains larger particles like bacteria and damaged cells. Lymph vessels connect to lymph nodes which filter the lymph and contain lymphocytes that fight infection. The largest lymph vessels are the thoracic duct and right lymphatic duct which drain lymph into the bloodstream. Disorders of the lymphatic system include lymphomas, lymphadenitis, and lymphedema.