Lymphatic system 101

The lymphatic system is actually part of the immune system and is involved in several different jobs. Using a network of vessels and organs, this system works to protect against infection, maintain body fluid levels, absorb digestive fats, and remove cellular waste.¹

In recent years it has been discovered that because of the network of vessels and connection to multiple organs and systems, the lymphatic system may also contribute to a number of health concerns, such as lymphedema and different inflammatory disorders.²

The lymphatic system is a network of vessels and organs. Unlike the blood vascular system, which is a circulatory system—the fluid (blood) leaves from and returns to the heart—the lymphatic system is linear. This means it is a one-way system. Excess fluid from cell metabolism and other waste is collected in fluid in the interstitial spaces of tissues and organs (lymph). This is then transported to thicker vessels that eventually return the fluid to the circulation system through the thoracic or lymphatic ducts.³

1. Lymph or lymphatic fluid —The extra fluid that drains from cells and tissues. It also carries proteins, minerals, fats, nutrients, damaged cells, and foreign invaders such as bacteria and viruses. Lymph also transports infection-fighting white blood cells.
2. Lymph nodes — The small glands that monitor and cleanse the lymph as it filters through the vessels.
3. Lymphatic vessels — The network of capillaries throughout the body that transport lymphatic fluid. They collect and filter lymph at the nodes and use a series of valves to keep the fluid moving in one direction.
4. Collecting ducts — These are located under the clavicle, and work to return lymph to the bloodstream, which helps to maintain normal blood volume and pressure and prevents excess buildup of fluid around the tissues (edema).
5. The spleen — The largest lymphatic organ, the spleen filters and stores blood and produces white blood cells that fight infection.
6. The thymus — This gland produces and matures a specific type of white blood cell.
7. Tonsils and adenoids are the body’s first line of defense. They trap pathogens from food and air.
8. Bone marrow — Produces white blood cells.
9. The appendix — Contains lymphatic tissue that can destroy bacteria before it breaches the intestinal wall.
10. Peyer’s patches — Small masses of lymphatic tissue in the mucosal membrane that lines the small intestine. These cells monitor and destroy bacteria in the intestines.¹

A main job of the lymphatic system, from a physiological point of view, is fluid regulation. The lymph vessels collect the fluid that leaks into the interstitial spaces of tissue and returns it to the blood system. When this process fails, lymphedema is the result – the collection of interstitial fluid in the tissues which causes swelling of the extremities.

• Lymphedema usually occurs when there is obstruction of the lymph vessel. Research suggests that this issue is often the result of breast surgery, where axillary lymph node dissection and radiation affect the upper extremity lymph system.⁴
• Inflammation is a response to tissue injury or infection. This provides two functions: One is to remove immune cells and inflammatory cytokines from the area. The other is to promote an immune response by connecting the affected site and the regional lymph node.²
• Lymph vessels are a pathway not only for the immune system, but for diseases as well. In fact, measuring metastasis to regional lymph nodes is a first step in monitoring tumor spread and can be an important indicator of cancer progression.²
• Because of the lymphatic system’s role in monitoring the uptake of lipids from the intestines, there is a suspected connection between lymphatic function and lipid (fat) homeostasis.²
• Recent studies suggest that due to the three separate lymphatic capillaries located in the intestinal wall, the pathophysiology of diseases such as Crohn’s disease and inflammatory bowel disease (IBD) are the result of some kind of lymphatic vasculature blockage or interruption.⁵

Obesity and a high-fat diet can create an accumulation of inflammatory cells around the lymphatic vessels, which then affects their collecting and pumping actions. This impaired lymphatic functioning that can happen with obesity may also contribute to the pathology of other systems in a domino-like effect, including hypertension, and diabetes.⁶

Research has also shown that chronic stress can drive cancer metastasis. The exact route of metastasis is still not completely clear, but research has shown an increase in neural-inflammatory signals which remodel lymphatic vessels and increase lymph flow which may provide a pathway for tumor cell metastasis.⁷

As mentioned, lymphedema is often associated with surgery. Patients experiencing this problem have found success incorporating yoga into their health routine, though the long-term benefits have not been studied.⁸

Good sleep hygiene is an integral part of a person’s health. Studies have shown that extended periods of sleep interruption, and the stress response that accompanies this deprivation, can cause persistent production of systemic inflammation which, as noted earlier, can impact proper lymphatic function.⁹

Lastly, regular exercise is necessary to move lymph fluid through the system, thereby supporting immunity, detoxification and healthy fluid levels.

In spite of not being as well known as the circulatory system, the lymphatic system has been receiving more and more attention in recent years. Composed of lymphatic tissues, vessels, fluids, and organs, the lymphatic system is responsible for not only immune support but fluid maintenance, fat metabolism, and waste removal. In the past few years, research has shown that certain diseases can use the vessels of the lymphatic system to spread. Understanding this process and how it works can go a long way toward finding effective treatments. There is an increasing amount of data to confirm that inflammation has a huge impact on how well the lymphatic system works (specifically in the functions of absorption and transportation of such diseases as Crohn’s and IBD).

At the same time, a balanced lifestyle which includes healthy stress relief, good eating habits, regular exercise, and quality sleep can contribute to a more efficient lymphatic system which in turn impacts overall immuno-health.

Sources:

1. Liao S, Padera TP. Lymphatic function and immune regulation in health and disease. Lymphat Res Biol. 2013;11(3):136-143. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3780287/
2. Cueni LN, Detmar M. The lymphatic system in health and disease. Lymphat Res Biol. 2008;6(3-4):109-122. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3572233/
3. Choi I, Lee S, Hong Y-K. The new era of the lymphatic system: no longer secondary to the blood vascular system. Cold Spring Harb Perspect Med. 2012;2(4):a006445. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3312397/
4. Kayıran O, De La Cruz C, Tane K, Soran A. Lymphedema: From diagnosis to treatment. Turk J Surg. 2017;33(2):51-57. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5508242/
5. Randolph GJ, Ivanov S, Zinselmeyer BH, Scallan JP. The lymphatic system: Integral roles in immunity. Annu Rev Immunol. 2017;35(1):31-52. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5551392/
6. Kataru RP, Park HJ, Baik JE, Li C, Shin J, Mehrara BJ. Regulation of lymphatic function in obesity. Front Physiol. 2020;11:459.https://www.frontiersin.org/articles/10.3389/fphys.2020.00459/full
7. Le CP, Sloan EK. Stress-driven lymphatic dissemination: An unanticipated consequence of communication between the sympathetic nervous system and lymphatic vasculature. Mol Cell Oncol. 2016;3(4):e1177674. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4972108/
8. Narahari SR, Aggithaya MG, Thernoe L, Bose KS, Ryan TJ. Yoga protocol for treatment of breast cancer-related lymphedema. Int J Yoga. 2016;9(2):145-155. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4959325/
9. Besedovsky L, Lange T, Born J. Sleep and immune function. Pflugers Arch. 2012;463(1):121-137. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256323/