Lymph Nodes

Along the lymph vessels are small swellings called lymph nodes. All lymph passes through at least one node before it is returned to the blood. Lymph nodes are found throughout the body, but they are clustered in particular places, including the neck, the armpits and the groin.Lymph nodes play a key part in defending the body against disease. They contain large numbers of white blood cells:Macrophages engulf and destroy pathogens, dead cells and debris by phagocytosis. As lymph filters slowly through the node, bacteria and other foreign particles are trapped and removed before the lymph returns to the blood.Lymphocytes recognise specific foreign antigens carried in the lymph. When lymphocytes meet an antigen they recognise, they are activated and divide rapidly, starting a specific immune response. Some lymphocytes produce antibodies, which are carried around the body.Because lymph from an infected area passes through the nearest nodes, this is where the immune response is often triggered. During an infection, the rapidly dividing lymphocytes make the nodes enlarge, which is why people often notice swollen, tender 'glands' in the neck when they have a sore throat.The lymphatic system can also carry cancer cells away from a tumour. Cancer cells can become trapped in the nearby lymph nodes and start secondary tumours there, so doctors often examine or remove nearby lymph nodes to find out whether a cancer has spread.