Question 4: How do lymph nodes work?

Jane Wigg RGN, MSc, Lymphoedema Clinical Expert, Answers L-W-O Community Member Questions


Lymph nodes are small bean size structures, placed around the body whose job is to filter the fluid that enters them and fight infection by producing immune cells protecting our bodies from infection and viruses.  

There are hundreds of nodes around the body, generally situated in your armpits, groin, neck, behind the knee and many deeper in the body around pelvis and the gut region.

We have about 600-700 lymph nodes. The most nodes I’ve seen reported in an armpit is 52, although usually it would be expected to be about 14-25 in the arm pit and 7-14 in the groin. There are hundreds to the head and neck region also. We all have an individual amount and we don’t really know whether if you have more or less of the normal number, if it increases or reduces your risk of developing a Lymphoedema.

The structure of the node is that it is formed of a strong outside of dense cells covered in a membrane forming a firm capsular. This is so that as it fills and reaches capacity, the pressure will change inside and force the fluid along or into the blood vessel running inside it.

The nodes will have 3-5 lymphatic vessels termed ‘afferent’ vessels entering into it and only one ‘efferent’ vessel leaving it which will be larger in size.

Flow into the node is not permanent, remembering that the collector draining to it will only empty when full. As there is not a constant flow to the nodes, each afferent vessel will deliver its fluid at different times as they are filled, meaning that one efferent vessel can cope with the exit fluid capacity and that fluid is also removed by the venous capillary.

The blood capillary that runs through it, feeds oxygen and plasma to the node and will exchange other cells and nutrients. 

The node is the only area of the lymphatic system where lymph can re-enter the circulatory system. Lymph entering the node contains water, white blood cells, sugars and salts, lipids (fats) and proteins. Of the fluid that enters the node, about 40% will leave through the venous capillary in the node. Due to the structure of the vessel, the smaller water and salts will leave making the lymph more concentrated as it leaves the node through the efferent vessel.

The node is made up of an inner and outer cortex, which stores lymphocytes (white blood cells) and other cells such as macrophages and dendrite cells that fight infection and destroy bacteria. 

Once the node has done its job of producing immune cells and filtering lymph, the fluid will continue its journey and leave either through the blood vessel returning to the heart or the ‘efferent’ vessel continuing along the lymphatic system.

As the nodes act as filter stations, they can become enlarged with bacteria. Lymph nodes are generally not able to be felt. Just sometime like a pea or bean under the skin in the area. They may become, sore, tender and swollen if you have an infection or cellulitis, and as they act as a collection point for cancer cells they may also become larger. You should palpate your nodes to know what is normal for you, and if you get any changes, let your therapist of medic know as soon as possible.

Lets take a closer look..


See you next month.

Jane Wigg


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