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 neck, armpit, groin, and 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 causes the nodes to swell. The swollen nodes are sometimes felt in the neck, under the arms, and groin.
The lymphatic system includes the tonsils, adenoids, spleen, and thymus.