The lymphatic system is responsible for returning excess fluid from body tissues to the circulatory system and for defending against foreign or harmful agents such as bacteria, viruses, or cancerous cells. The major components of the lymphatic system are lymph capillaries, lymph vessels, and lymph nodes. Lymph is a clear fluid found in tissues that originates from the circulatory system. Lymph capillaries are tiny vessels that carry excess lymph to larger lymph vessels; these in turn empty to the circulatory system.