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The lymph system is a network of organs, lymph nodes, lymph ducts, and lymph vessels that produce and transport lymph from tissues to the bloodstream. The lymph system is a major component of the body's immune system.

Lymph is a clear-to-white fluid made of:

• Fluid from the intestines called chyle, which contains proteins and fats
• White blood cells, especially lymphocytes, the cells that attack bacteria in the blood

Lymph nodes are small, bean-shaped, soft nodules. They can not usually be seen or easily felt. They are located in clusters in various parts of the body, such as the neck, armpit, groin, and inside the center of the chest and abdomen.

Lymph nodes produce immune cells that help the body fight infection. They also filter the lymph fluid and remove foreign material such as bacteria and cancer cells. When bacteria are recognized in the lymph fluid, the lymph nodes produce more infection-fighting white blood cells, which causes the nodes to swell.

The lymphatic system includes the tonsils, adenoids, spleen, and thymus.

See also:

• Lymphangioma
• Lymphedema
• Lymphoid hyperplasia

Armitage JO. Approach to the patient with lymphadenopathy and splenomegaly. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 147.

Updated by: A.D.A.M. Editorial Team: David Zieve, MD, MHA, Greg Juhn, MTPW, David R. Eltz. Previously reviewed by David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine (10/18/2008)