The lymphatic system

Lymph fluid Back to top

This is the liquid that flows through the lymph vessels and the lymph nodes. It forms when excess liquid that surrounds all our body tissues drains into small lymph vessels.

Lymph vessels Back to top

These are tiny channels which usually lie just under the skin. They can be easily damaged if the skin is broken. Small lymph vessels join together to form larger lymph vessels, which pass through a number of lymph nodes. In the lymph nodes, bacteria and harmful substances are broken down. The fluid then travels through larger lymph ducts and drains into the bloodstream.

Lymph nodes Back to top

Lymph nodes are found throughout the body, but mainly in the neck, armpit, groin and tummy (abdomen). They’re made of tissue that contains special cells that help fight infection and disease such as cancer.

Lymph nodes vary in size; some are as small as a pinhead and others are about the size of a baked bean. The number of lymph nodes in the body varies from person to person. Different parts of the body also have different numbers of nodes; in the armpit, for example, there are about 15-30 small nodes.

Lymph fluid flows through the lymph nodes, which act as a filter by destroying or trapping anything harmful that the body doesn’t need. This includes bacteria, viruses, damaged cells or cancer cells.

Lymph nodes contain white blood cells (lymphocytes), which attack and break down bacteria or other harmful cells. Waste products and the destroyed bacteria are then carried in the lymph fluid into the bloodstream and are disposed of with other body waste.

Sometimes the lymph nodes trap bacteria or viruses that they can’t destroy immediately. The lymph node will then usually swell, and become tender and sore to touch. This is usually the sign of an infection which may need treatment with antibiotics.

Sometimes cancer cells spread into the lymph nodes from a cancer in another part of the body. It’s also possible for a cancer to start in the lymph nodes themselves (lymphomas). If this happens, the lymph nodes become swollen but are usually painless.

There are different causes for swollen lymph nodes, but if you do develop a painless, swollen lymph node it’s important to have it checked by your GP.