How the Body Works : The Lymphatic System

The lymphatic system, a network of vessels which carries lymph from around the tissues to the blood, has valves which prevent backflow. Lymph is formed when high arterial pressure forces fluid out of the capillaries and into the tissue spaces. From there it is taken up into the lymphatic vessels. The lymph carries harmful substances from the tissues to the lymph nodes, for removal, before the lymph is returned to the blood at the veins in the neck. In the lymph nodes there are large numbers of white blood cells which produce antibodies and ingest any foreign material.