The lymph system is a network of organs, lymph nodes, lymph ducts, and lymph vessels that make and move lymph from tissues to the bloodstream. The lymph system is a major part of the body's immune system.
Lymph is a clear-to-white fluid made of:
- White blood cells, especially lymphocytes, the cells that attack bacteria in the blood
- Fluid from the intestines called chyle, which contains proteins and fats
Lymph nodes are soft, small, round- or bean-shaped structures. They usually cannot be seen or easily felt. They are located in clusters in various parts of the body, such as the:
- Inside the center of the chest and abdomen
Lymph nodes make 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 make more infection-fighting white blood cells, which cause the nodes to swell. The swollen nodes are sometimes felt in the neck, under the arms, and groin.
The lymph system includes the:
Hall JE. The microcirculation and lymphatic system. In: Hall JE, ed. Guyton and Hall Textbook of Medical Physiology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 16.
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.