What Does the Lymphatic System Do?

The Lymphatic system plays two main roles, one is immunity, which most people are fairly familiar. The other role is transport. This system is responsible for returning 10% of the fluid pumped into our tissue from our heart. Our veins are designed to return the rest of it, about 90%. When needed, the lymph system can accommodate a higher volume for short periods of time. The role of transport of the lymphatic system is significant not only in volume of fluid it carries, but what it carries. It transports large protein molecules, both those that leak into the tissue from blood circulation and as a result of injury/ surgery. The lymphatic system is the only system in the body that can recuperate these proteins, too large to fit through the veins. It is this balance of proteins that keeps our tissue from swelling up on a daily basis.

The Lymphatic system is where many of the bodies healing resources are found and operate. 85% of the cells in the lymphatic system are designed to protect our body from foreign matter and eliminate it. Many of these and additional immune cells frequent the 400 – 1000 lymph nodes in the body, where foreign matter is often stored.

The Lymph System and Protein

When the body gets injured and tissue is damaged or torn, fluid leaks into it. With every injury, protein molecules spill into the tissue space from broken cells and blood vessels. The collective ‘spilled’ fluid at the injury site is called exudate or ‘primary edema’. Much of this protein is reabsorbed or used in the repair process. This protein ultimately becomes very popular with water molecules and soon after the injury, for up to 24-48 hours , an influx of water molecules progressively gravitates to the injured area in the attempt to dilute this concentrated solute. This influx of fluid becomes the ‘secondary edema’. It is called secondary because it is not part of the initial injury, but rather is the body’s attempt at helping to dilute this concentration of protein. It is this ‘secondary’ fluid that can be so obvious in injuries like ankle sprains.

Problems with Protein

Swollen tissue over time is not healthy. The tissue does not get adequate nutritive exchange and this can lead to hypoxic tissue and cell deterioration. Hypoxic tissue can lead to the development of adhesions and restrictions in the connective tissue. Early lymphatic drainage during the rehabilitation process can minimize these effects.

The Lymphatic System as an Internal ‘Shop Vac’

Have you ever tried siphoning fluid from one container to another? Put one end of a tube in a bucket of water and place your mouth over the other tube opening. Inhale through your mouth. You are creating a pressure differential between the ends of the tube. As you inhale you are creating a ‘vacuum’ or ‘lower’ pressure at the mouth end of the tube in comparison to the now ‘higher’ pressure at the water end. As the difference in pressure increases, water begins to migrate through the tube, eventually flowing from the bucket out the tube.

The lymphatic system functions on a pressure differential too. There is always a lesser pressure at one end of the lymphatic system (towards the lungs) and a higher one at the other (in the abdomen and extremities). The open end lies extensively through a loose network throughout your cells and tissue. The other end culminates under your collarbone where it flows into your veins and circulatory system. Manually, this pressure differential can be increased by techniques at the neck. This initiates the ‘siphon’ effect, increasing the flow rate of the lymphatic system.

Increased flow rate causes increased contraction in the muscles of the deeper vessels, furthering the rate of circulation. The ‘at rest’ rate of 1.5-2.0 liters circulating through the system per day can increase to 10 – 30 liters. Palpating the tissue of an arm or a leg both before and after a session (40-60 minutes), there can be a dramatic change in the feel of the tissue as a result of this increased drainage rate. Tissue becomes relaxed, looser and more mobile than it was. It really feels as if there is an internal ‘shop vac’ drawing up fluid in the tissue. With conditions that have black and blue bruising, the color can sometimes be seen moving underneath the tissue and the color transition to yellow-green can be seen.

The effectiveness of the lymphatic system at rest is often mitigated flying on a commercial aircraft. Due to the cabin pressurization, and so less pressure differential than on the ground (one atmosphere), the lymphatic system works less effectively. Combined with long term sitting, this can result in increased swelling in our legs (shoes getting tight!).

Archer, P. (2006). Therapeutic Massage in Athletics. Lippincott Williams & Wilkins.
Chikly, B. (1996). Lymph Drainage Therapy. UI Publishing.
Foldi, M. (2005). Foundations of Manual Lymph Drainage, 3e. Elsevier Mosby.
Guyton, A. & Hall, J. (2000). Textbook of Medical Physiology, 10e. Saunders.
Knight, K. (1978). Relevant topics in athletic training. Mouvement Publications.

End Notes

Bruno Chikly, Lymph Drainage Therapy (UI Publishing, 1996), 4
Chikly, 4.
Chikly, 4.
Chikly, 1.
Chikly, 4.
Chikly, 3.
Pat Archer, Therapeutic Massage in Athletics (Lippincott Williams & Wilkin, 2006),
Chikly, 4.
Kenneth Knight, Cryotherapy in Sports Medicine (1978), reprinted by permission Brenneke School of Massage, 405