There are more than 600 lymph nodes throughout the body. They are a part of the lymphatic system, a network of vessels responsible for carrying a clear liquid called lymph into the skin cells and throughout the organs. Lymph nodes contain millions of infection-fighting cells called lymphocytes. When the body contracts an infection or disease, the lymphocytes act as filters, trapping the infection, virus, or bacteria, and swell as a result. Swollen lymph nodes are called lymphadenopathy.
Swollen lymph nodes are not a disease, but a symptom of an illness or an infection. Fungal infections, bacterial infections, or viral infections can cause the lymph nodes to swell, announcing the presence of a condition such as an upper respiratory infection, tonsillitis, or conjunctivitis. Which lymph nodes swell indicates the location of the infection; for instance, if there is a swollen lymph node in the jaw area, the infection likely affects the mouth or the teeth. In most cases, lymphadenopathy is not serious.
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