Re: Why do lymph nodes become swollen?

Jim,

Lymph nodes can become large enough to feel due to infections and cancers.

The lymph nodes are part of the immune system. The lymhatic vessels form a system much like the blood vessel system. They drain lymphatic fluid from around the cells from almost every part of the body. The lymphatic fluid collects into ever larger vessels and eventually drains into the large veins near where the veins drain into the right side of the heart. The lymph nodes act like strainers or seives and intercept noxious agents like bacteria, viruses and other foreign substances.

The lymph nodes are aggregates of lymphocytes. The lymphocytes are white blood cells that combat infections. Collections of lymph nodes that you can feel are located in the neck, arm pit and at the top of the thigh. Inside the body they are distributed along the larger vessels.

If an infection starts at some place in the body, the infective particles are carried by the lumphatic fluid to the lymph nodes. There, the lymphocytes may multiply to combat the infection. The lymph node may become large enough to feel. Cancers may also spread by way of the lymphatic system and lodge in the nodes making them big. There is also a cancer of the lymhpocytes themselves, called lymphoma, which can make the lymph nodes big.

Lymph nodes that become enlarged without an obvious infection nearby should be evaluated by a physician.