See also lymphadenitis and lymphangitis . The lymphatic system is a complex network of thin vessels, valves, ducts, nodes, and organs. It helps to protect and maintain the fluid environment of the body by producing, filtering, and conveying lymph and by producing various blood cells. The lymph system is present throughout the body.
Lymph nodes play an important part in the body's defense against infection.
Swelling might occur even if the infection is trivial or not apparent. Swelling of lymph nodes generally results from localized or systemic infection, abscess formation, or malignancy . Other causes of enlarged lymph nodes are extremely rare. By far, the most common cause of lymph node enlargement is infection. As a rule, when swelling appears suddenly and is painful, it is usually caused by injury or an infection.