The lymphatic system is complex network of thin vessels, capillaries, valves, ducts, nodes and organs that runs throughout the body, helping protect and maintain the internal fluids system of the entire body by producing, filtering and conveying lymph and by producing various blood cells.

The three main purposes of the lymphatic system are to drain fluid back into the bloodstream from the tissues, filter lymph and fight infections.

This system, which includes the spleen, the thymus, lymph nodes and lymph ducts, is a major component of the immune system.

The lymphatic system branches through all parts of the body carrying lymph, a milky fluid made of chyle (intestinal fluid produced after digestion, containing fats and proteins). Lymph contains red blood cells and many white blood cells, especially lymphocytes. Lymphocytes are the cells that attack bacteria in the blood.

Lymph is produced by small bean-shaped "lymph nodes...