The lymphatic system is part of the circulatory system, comprising a network of lymphatic vessels that carry a clear fluid called lymph (from Latin lympha meaning water)) directionally towards the heart. - Wikipedia
The lymphatic system is an integral part of the immune system and it plays an important part in the body’s defence against disease - The Human Body Book p 156
So, it’s part of the immune system, and part of the circulatory system, and works quite like the circulatory system (think heart, veins, arteries etc) but with a couple of key differences.
Number 1 - it is not a closed loop.
In my eyes, the greatest difference between our circulatory and lymphatic systems is that the former is a closed loop. This means that the blood, whether oxygenated or deoxygenated, never leaves the arteries, veins or capillaries. Lymph is a clear fluid that circulates around the body tissues, and drains into lymph vessels, which are much finer than the cardiovascular vessels.
A quick aside about ‘interstitial fluid’ - this is the fluid that bathes and surrounds our cells & “consists of a water solvent containing sugars, salts, fatty acids, amino acids, coenzymes, hormones, neurotransmitters, as well as waste products from the cells” - Wikipedia
Number 2 - there is no pump.
The circulatory system is governed by the heart, which pumps around 20 litres of blood around our body with each beat. Cast your minds back to biology lessons and you’ll remember that the heart pumps oxygenated blood to the body and deoxygenated blood to the lungs. Oh, and there are two types of vessels the blood travels through, arteries and veins - the big difference between the two is that veins return to the heart and therefore are under less pressure from the force of the heart pumping, so have ‘non-return valves’ to keep the blood moving (a little like canal locks).
When the system is working well, our interstitial liquid is drawn into the lymph vessels and up towards the heart, where the extra fluid returns to the circulatory system. When we move, our muscles can act as a pump to help move the fluid through the vessels (which have no valves) so although they act as a ‘pump’, we have no ‘lymph heart’ (random fact … unlike lungfish, all amphibians, reptiles and flightless birds which all have a lymph heart, apparently! I guess they don’t move enough for their muscles to exert enough pumping action.)
Number 3 - it’s job is primarily defensive
Unlike the circulatory system which is like the motorway network (on a good day) which is all about keeping the traffic moving, the job of the lymphatic system is more like customs (again on a good day!). The purpose of the lymphatic system is basically:
- To return ‘interstitial’ fluid and lymph to the bloodstream.
- To transport fatty acids from the intestines to the circulatory system.
- To filter and clean the lymph of any debris, abnormal cells or pathogens.
- To transport white blood cells to and from the lymph nodes into the bones.
In the undertaking of the latter, the lymphatic system acts to protect our bodies from invading forces.
So, what’s all the fuss?
Oedema is actually what used to be referred to as ‘dropsy’ or ‘hydropsy’! According to NHS Choices today - “Oedema is the medical term for fluid retention in the body” while “Lymphoedema is a chronic (long-term) condition that causes swelling in the body's tissues. It can affect any part of the body, but usually develops in the arms or legs.”
When there is an accumulation of lymph fluid in the tissues, resulting from the poor or inadequate draining of the lymphatic system, it will typically be accompanied by some local swelling, and perhaps even some pain or heaviness. Fundamentally, it can be uncomfortable.
It is normal to have mild swelling at the end of the day, particularly if you’ve been sitting or standing for long periods of time. The issue surrounding oedema is typically seeking the cause of the swelling, i.e. what is the oedema symptomatic of? It could be the perfectly normal part of our body’s ebb and flow, but it can indicate an underlying health issue which may be impacting on your immune system - for more information, the NHS Choice page is a good start, and if you have any concerns at all then I would suggest to discuss these with your GP or other medical professional.
The most common form of oedema is in the feet and ankles (the kind pregnant ladies regularly experience towards the end of pregnancy as the weight of the baby presses and inhibits the inguinal lymph nodes), or perhaps in the a hand or arm post surgery related to breast cancer treatment including lymph node removal. Peripheral oedema such as these symptoms are the most common, and affect the limbs. Whilst there are other types, this is the form of oedema I am referring to for the rest of this article.
Oedema typically clears up on it’s own and is not usually anything to worry about. There are things you can do to help (which I will outline in my DIY Lymph Drainage article), but if you find that its a persistent issue for you, or you feel concerned at all, get it checked out by your pharmacist or GP. However there are a couple of additional symptoms which, if you came to me for a massage and I spotted, I’d suggest you seek advice for rather than receiving massage - symptoms which I refer to as ‘red flags’:
If you press a finger into the swelling, and it doesn’t leave a mark / indentation when it is removed, then this is non-pitting oedema, however if a mark or indentation is left and takes a while to go, then this could be an early sign of lymphoedema or cellulitis, and medical advice should be sought before proceeding with any exercises or therapies.
Thin, shiny looking skin around the area is pretty normal because the layers are being stretched over a larger surface area than normal, but any signs of inflammation, redness, heat or weeping through the surface of the skin should be treated with respect and medical advice sought.