The lymphatic system is part of the body’s immune system. It helps to protect us from infection and disease. The lymphatic system also drains fluid from the body’s tissues back into the blood.
A diagram showing the network of lymph nodes throughout the body:
The lymphatic system includes:
- lymph vessels
- lymph nodes (sometimes called lymph glands)
- lymphocytes (blood cells that fight infection)
- lymphatic organs
- other lymphatic tissue.
Lymph vessels are fine tubes that form a network inside the body. A clear fluid called lymph moves through the vessels and nodes and eventually returns to the bloodstream.
There are groups of lymph nodes around the network. As the lymph fluid passes through the nodes, they filter out disease and germs (bacteria and viruses). The lymph nodes contain infection-fighting white blood cells called lymphocytes. Lymph nodes often swell when they are fighting infection. If you have a throat infection, you may be able to feel swollen lymph nodes in your neck below your jaw.
Lymphatic organs include the thymus, which helps some types of lymphocytes to mature. They also include the spleen and the tonsils, both of which help fight or filter out disease and germs.
The bone marrow is the spongy material in the middle of bones. It makes:
- all the different types of white blood cell including lymphocytes
- red blood cells, which carry oxygen from your lungs to other cells in your body
- platelets, which help blood to clot and prevent bleeding and bruising.
There are also other areas of lymphatic tissue where lymphocytes and other infection-fighting cells collect. These areas are mostly found where disease or germs are more likely to enter the body – for example, in the lining of the bowel, lungs and nose.