The lymphatic system is made up of a vast network of vessels, similar to blood vessels that branch out into all the tissues of the body.

It drains fluid (called lymph) that has leaked from the blood vessels into the tissues and empties it back into the bloodstream via the lymph nodes.

Lymph is a colourless watery fluid that carries lymphocytes, specialised white blood cells that fight infection. Lymphocytes help fight disease and infection by making antibodies and destroying bacteria and viruses.

Your lymph nodes are small bean-shaped organs that can be found throughout your body including your throat, armpits, chest, groin and abdomen. There are between 600 and 700 lymph nodes in your body and they are usually clustered in chains or groups and found in fatty tissue near veins and arteries.

Some of their functions include:

• Filtering lymph before returning it to the bloodstream and removing dead cells
• Detecting and destroying infectious agents, such as bacteria or viruses
• Detecting and destroying faulty cells, such as cancer cells
• Maturing B-lymphocytes (B-cells).

Because lymph nodes are filled with lymphocytes, they are associated with body defense. Lymphocytes can rapidly multiply and release antibodies in response to bacteria, viruses, and a range of other stimuli from dead or dying cells and abnormally behaving cells such as cancer cells. This is why your lymph nodes swell when you have an infection or other threat.

Other organs involved in the lymphatic system include the spleen and the thymus. The spleen filters and monitors your blood, stores lymphocytes, and destroys old or damaged red blood cells. The thymus also filters and monitors your blood and is where T-cells are matured.