The lymph system is a network of vessels and organs throughout the body. This system carries lymph fluid, nutrients, and waste material between the body tissues and the bloodstream.

The lymph system includes the lymph nodes, tonsils, thymus, spleen, and bone marrow. The lymph nodes filter lymph fluid as it flows through them. The nodes trap bacteria, viruses, and other foreign substances, which are then destroyed by special white blood cells called lymphocytes.

The lymph system is also an important part of the immune system, the body's defense against disease. When there is a problem in the body, the nearby lymph nodes may become swollen. For example, if a person has a throat infection, lymph nodes in the neck may swell and become tender.

Sometimes diseases, like cancer, can begin in the lymph system or spread to it.