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Body contours, swollen lymph nodes and dehydration, 3 facts about the lymph system you may not know.

Updated: May 17, 2023

Fact 1: Constant lymph pumping creates the superficial contours of your body, allowing tendons and veins to stand out, and creating the hollows behind your ankles.

The lymphatic system is arranged into superficial and deep systems which are divided by the deep fascia, a very tough elastic stocking enclosing your muscle body and all your vital organs.

Lymph nodes and vessels under the the deep fascia are in the deep system.


Under this inner elastic bodysuit, the muscles and organs are in a high pressure environment which supports lymph flow and venous return. Especially when your muscles are working and creating a lot of pressure variation underneath.

The superficial system is everything above the deep fascia and under the skin.

The skin is not such a 'tight stocking' as the deep fascia and doesn't create a high pressure environment in the superficial system. This means that many more lymph vessels are needed to remove and transport the tissue fluid.

80% of all lymph vessels in your body are in the subcutaneous compartment where the initial lymph plexus branches densely just a few mm below the skin.


This covering of fine lymph vessels plays an important role in your body's defences by quickly removing anything harmful that crosses the skin barrier, and transporting them toward the major lymph node basins. The transporting collector vessels travel just above the deep fascia where they also benefit from skeletal muscular activity,

Although lymphatic pumping is a slow, low pressure activity, it is continuous and never stops.

Clipart Image from Microsoft PowerPoint

Constant lymphatic pumping creates a suction force in the subcutaneous tissue, literally vacuum cleaning the under-surface of your skin to suck out pathogens, proteins and free water circulating through the tissues. This results in a slightly sub-atmospheric pressure in the loose connective tissue (LCT). The slightly higher pressure of the atmosphere is able to compresses the softer LCT tissue slightly, but hard structures like tendons, and high pressure vessels like veins are not compressed. These structures stand out and hollows form behand the ankles at the base of the neck.

The loss of these fine contours are among the first noticeable changes that occur during lymphatic failure.


Fact 2: Lymphatic endothelial cells can detect the contents of the lymph, influence smooth muscle in the lymphangions, and contribute to lymph node swelling.

The endothelial cells lining all lymph vessels are constantly monitoring the contents of the lymph and communicating with the smooth muscle in the vessel wall. This contributes to the normal coordination of lymph pumping and is very important to maintaining lymph flow.

During infections, endothelial cells in the efferent vessels can signal the angions to contract if a high pathogen load is detected.

Excess pathogens in the efferent lymph are an indication that the infection has not yet been fully processed by immune elements within the lymph node. Vaso-constriction of the efferent vessels traps the harmful material inside the node for more processing.

Fresh lymph continues to enter the node which swells to accommodate the increased load.


Once the infection is brought under control and the harmful material has been properly processed the endothelial cell signalling stops, normal lymph pumping resumes and the swollen node reduces. Lymph nodes can also grow to accommodate the volume of pathogenic material they must process, especially if the infection is severe or prolonged. Lymph nodes which have undergone this kind of growth will not reduce back to their original size after the infection is cleared and will remain as larger lymph nodes.


Fact 3: Your lymph system protects tissue cells from dehydration and supports venous return.

The loose connective tissue is comprised of tissue fibres and cells, and the exact composition and architecture will vary depending on location. In the subcutaneous tissue the dominant cell type are often fat cells which form the padding and insulating layers of the body.

Regardless of location or type of connective tissue, the space between the fibres and cells is filled with an amorphous ground substance comprised of large glucos-amino-glycan (GAG) molecules, principally hyaluronic acid (HA). These huge molecules have a bottle-brush like structure with millions of fibres that can attach and hold free water to protect the tissue cells from dehydration. Read more about HA in other #TalkingLymph posts. If you are dehydrated the HA takes up any free water molecules in the tissue to hold them in close proximity to the cells, which are very susceptible to dehydration.

Up all night in the bathroom? Dehydration during the day will make this worse.


During the day water is held by the HA as a buffer against dehydration and to meet cellular demand. When you go to bed and your body is at rest, cellular demands are lower and some of the free water can be released. When you horizontal the lower peripheral blood pressure allows the free water to be resorbed into the veins, returned to circulation and excreted by the kidneys.

Frequent hydration during the active part of the day will allow normal fluid movement through the connective tissue and prevent excess water being bound by the HA to prevent dehydration.

This will reduce night time frequency for many.



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