The lymphatic system
The lymphatic system is one of the body’s natural defences against infection and disease.
The lymphatic system is made up of:
lymph nodes (sometimes called lymph glands)
lymphocytes (blood cells that fight infection)
Lymph vessels are fine tubes similar to small blood vessels. They join together to form a network that runs throughout the body. The lymph vessels act like a transport system for a fluid called lymph, which surrounds cells and tissues in the body. The lymph vessels drain lymph from the tissues into the blood as it circulates the body.
There are groups of small bean-shaped organs called lymph nodes all along the lymph vessels. Lymph nodes filter lymph as it passes through them, removing any debris. The main groups of lymph nodes are in the neck, armpit, chest, tummy area (abdomen) and groin (see diagram on the next page).
There are white blood cells called lymphocytes inside the lymph nodes. As lymph passes through the nodes, the lymphocytes fight any infection they find and stop it travelling around the body. When lymph nodes are fighting an infection, they get bigger and feel tender. For example, people often get tender, swollen glands (lymph nodes) in their neck when they have a throat infection.
Lymphocytes are mainly found in lymph nodes, but they also travel around in the blood and lymph. There are two main types of lymphocyte: B-cell lymphocytes and T-cell lymphocytes.
Lymphatic tissue is a special type of tissue that helps combat infection. It’s found in lymphatic organs such as the spleen, bone marrow, tonsils and thymus. There’s also lymphatic tissue in other parts of the body, including inside the lining of the stomach and bowel, around the eye, in the thyroid gland, and in the testicles.
The bone marrow, a spongy material inside the bones, is also part of the lymphatic system. All the body’s blood cells, including lymphocytes, are made inside the bone marrow.