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What the lymphatic system is
The lymphatic system is a system of thin tubes and lymph nodes that run throughout the body. These tubes are called lymph vessels or lymphatic vessels. The lymph system is an important part of our immune system. It plays a role in:
- fighting bacteria and other infections
- destroying old or abnormal cells, such as cancer cells
The lymphatic system
The diagram shows the lymph vessels, lymph nodes and the other organs that make up the lymphatic system.
How it works
The lymphatic system is similar to the blood circulation system. The lymph vessels branch through all parts of the body like the arteries and veins that carry blood. But the lymphatic system tubes are much finer and carry a colourless liquid called lymph.
The lymph contains a high number of a type of white blood cells called lymphocytes. These cells fight infection and destroy damaged or abnormal cells.
As the blood circulates around the body, fluid leaks out from the blood vessels into the body tissues. This fluid carries food to the cells and bathes the body tissues to form tissue fluid. The fluid then collects waste products, bacteria, and damaged cells. It also collects any cancer cells if these are present. This fluid then drains into the lymph vessels.
The lymph then flows through the lymph vessels into the lymph glands, which filter out any bacteria and damaged cells.
From the lymph glands, the lymph moves into larger lymphatic vessels that join up. These eventually reach a very large lymph vessel at the base of the neck called the thoracic duct. The thoracic duct then empties the lymph back into the blood circulation.
Lymph nodes (lymph glands)
The lymph glands are small bean shaped structures, also called lymph nodes.
There are lymph nodes in many parts of the body including:
- under your arms, in your armpits
- in each groin (at the top of your legs)
- in your neck
- in your tummy (abdomen), pelvis and chest
You may be able to feel some of them, such as the lymph nodes in your neck.
The lymph nodes filter the lymph fluid as it passes through them. White blood cells, such as B cells and T cells, attack any bacteria or viruses they find in the lymph.
When cancer cells break away from a tumour, they may become stuck in one or more of the nearest lymph nodes. So doctors check the lymph nodes first when they are working out how far a cancer has grown or spread.
When the lymph nodes are swollen, doctors call it lymphadenopathy. The most common cause is infection but lymph nodes can also become swollen because of cancer.
Other lymphatic system organs
The lymphatic system includes other organs, such as the spleen, thymus, tonsils and adenoids.
The spleen
The spleen is under your ribs, on the left side of your body. It has 2 main different types of tissue, red pulp and white pulp.
The red pulp filters worn out and damaged red blood cells from the blood and recycles them.
The white pulp contains many B lymphocytes and T lymphocytes. These are white blood cells that are very important for fighting infection. As blood passes through the spleen, these blood cells pick up on any sign of infection or illness and begin to fight it.
The thymus
The thymus is a small gland under your breast bone. It helps to produce white blood cells to fight infection. It is usually most active in teenagers and shrinks in adulthood.
The tonsils and adenoids
The tonsils are 2 glands in the back of your throat.
The adenoids are glands at the back of your nose, where it meets the back of your throat. The adenoids are also called the nasopharyngeal tonsils.
The tonsils and adenoids help to protect the entrance to the digestive system and the lungs from bacteria and viruses.
