Overview
The lymphatic system is a network of tissues and organs that are essential for immune function, fluid balance, and lipid absorption. This complex system is made up of lymph nodes, lymphatic vessels, lymphocytes, the thymus gland, adenoids, tonsils, the spleen, and bone marrow.1 Lymph fluid, a clear fluid that circulates through lymphatic vessels and contains infection-fighting white blood cells, is an essential component. When functioning properly, the lymphatic system often goes unnoticed, but it is essential for transporting fluid, filtering waste, and protecting us from disease and injury.1
The lymphatic system and edema
To maintain fluid homeostasis, the lymphatic system drains excess interstitial fluid from body tissues and returns it to the bloodstream. Every day, approximately 2 to 3 litres are returned to circulation via the lymphatic system.1 When lymphatic vessels are damaged or obstructed because of surgery, infection, malignancy, or immobilisation, the lymphatic system cannot effectively drain lymph fluid.
Components and organisation of the lymphatic system
The lymphatic system is a network of tissues, organs, and vessels that maintains the body's fluid balance, absorbs fats and lipids, and defends against microorganisms.2 These are the primary structural components of this system.
Similar to blood vessels, lymph vessels are a network of thin channels that transport lymph fluid throughout the body.3 They consist of larger collecting vessels and small lymphatics or capillaries that absorb lymph from tissues. Additionally, lymph trunks discharge into lymph ducts that connect to veins.
Lymph Nodes - Small, bean-shaped organs located along lymph vessels and responsible for filtering lymph. They contain lymphocytes, which eliminate unwanted substances, debris, and microorganisms. Hundreds of lymph nodes are dispersed throughout the body.4
Lymph - A transparent fluid derived from interstitial fluid that circulates through the lymphatic system. It is composed of white blood cells, proteins, lipids, and dead organic particles.5
Tonsils/Adenoids - Clusters of lymphatic tissue in the throat that can recognise and eliminate invading pathogens as lymph passes.6 Moreover, located behind the sternum, the thymus gland produces T lymphocytes for the immune system.7 Furthermore, the spleen is an abdominal organ that filters blood and stores lymphocytes to combat infection.8 Additionally, in bone marrow, stem cells produce new blood cells, lymphocytes, and plasmacytes.9
These lymphatic structures function as a vascular drainage network to regulate fluid balance, transport lipids, and safeguard the body from disease and inflammation.10
Functions of the Lymphatic System
Fluid equilibrium and circulation
Maintaining fluid homeostasis is one of the lymphatic system's most important functions.2 It functions as a one-way drainage system that returns excess interstitial fluid from tissues to the circulatory system. Without this drainage mechanism, fluids and proteins would accumulate in the tissue spaces, resulting in a dangerous condition called edema.11
The lymphatic capillaries, or initial lymphatics, absorb excess protein-rich fluid and pass it through lymph vessels that become progressively larger.11 The fluid, now known as lymph, is filtered by lymph nodes before being returned to the circulatory system through the subclavian vessels.11,12 Additionally, the lymphatic system returns plasma proteins that have leaked out of blood capillaries back into circulation, thereby aiding in the maintenance of a healthy blood colloid osmotic pressure.
Immune system assistance
The lymphatic system is an essential component of the immune system.13 Lymph nodes filter lymph fluid and capture microorganisms, debris, and other pathogens. Lymphocytes such as T cells and B cells encounter and eliminate foreign invaders within the lymph nodes. These infection-fighting cells migrate from the blood and lymph node reserves into the lymph fluid. The lymph then transports the lymphocytes throughout the body to provide immune surveillance.14 The lymphatic system and immune system function closely together to protect the body from pathogens and toxins.
Elimination of wastes and toxins
When interstitial fluid enters lymphatic capillaries, it carries metabolic waste products, bacteria, damaged cells, and cellular debris.15 Before the fluid is returned to the bloodstream, the lymph nodes filter and capture these waste products and contaminants and purify the lymph. Additionally, at sites of injury or inflammation, the lymphatic system eliminates cellular remnants and detritus to assist in the resolution of the inflammatory response. This function of waste removal keeps tissues pure and healthy.16
What causes oedema related to the lymphatic system?
Oedema refers to tissue swelling caused by fluid accumulation.2 The lymphatic system is frequently impaired in these cases. When the lymphatics are unable to effectively discharge this fluid, it accumulates and causes swelling. Several critical factors can cause damage to lymphatic vessels or lymph nodes, resulting in lymphedema or swelling; these include:
Bacterial infections such as cellulitis can lead to lymph node and vessel inflammation and obstruction.17 As lymph nodes become swollen in response to an infection, their capacity to filter lymph fluid decreases.18 The inflamed vessels would also struggle to transport fluid. Additionally, infection increases the permeability of blood vessels, which forces more fluid into the tissues. This combination of excessive filtration and diminished lymphatic drainage results in significant oedema.
Cancer - Malignant tumours frequently disseminate to lymph nodes, displacing healthy tissue and compressing lymphatic vessels.19 This obstruction impedes the effective drainage of fluids through the lymph nodes. The removal of lymph nodes during cancer surgery also damages or severs lymphatic channels.20
Injury/surgery - Any incision or trauma that damages the complex network of lymphatic capillaries and vessels inhibits their vital drainage function.21 Blunt trauma, burns, and orthopaedic surgery bear a high risk of interfering with lymphatic flow and causing swelling. Scarring from surgery or radiation therapy can also contribute to lymphedema by compressing lymphatic vessels.22
Simple inactivity inhibits the contraction of muscles that ordinarily pump lymph fluid through lymphatic vessels.23 Therefore, paralysis, protracted bed rest, and a sedentary lifestyle can reduce this pumping action and permit fluid accumulation.
Function of the lymphatic system in oedema management
The lymphatic system is essential for preventing and treating oedema. Here are a few of its principal functions:
Drainage and shipping
The network of lymphatic capillaries absorbs excess fluid, proteins, and waste products from the interstitial space and transports them to lymph nodes for filtration.15 Without this constant one-way drainage, fluid would accumulate and produce swelling in the tissues.
Management of fluid balance
Approximately 1-2 litres of fluid are returned to the bloodstream via the lymphatic system daily.2 This system maintains the equilibrium of fluid levels between the blood and interstitial compartments.12 Ineffective lymphatic drainage results in fluid accumulation in the tissues.
Elimination of proteins
The lymphatics return plasma proteins that have leaked from blood vessels into the bloodstream. This facilitates the maintenance of oncotic pressure gradients between blood and tissue.11 Inadequate lymphatic drainage causes tissue protein accumulation, which increases oncotic pressure and fluid retention.
Management of inflammation
Lymphatic vessels remove excess fluid, inflammatory mediators, and debris from inflammatory and infectious sites.13 This reduces oedema and facilitates the healing process.
When lymphatic vessels or nodes are damaged or overloaded, drainage and conveyance of fluid become stagnant, resulting in oedema with high protein content. Chronic swelling conditions, such as lymphedema, are frequently treated with therapies that improve lymphatic flow.
The impact of common injuries on the lymphatic system
Surgical Procedures/Incisions
Surgical incisions disrupt lymphatic vessels traversing the epidermis and subcutaneous tissues.24 This injury can inhibit lymph drainage from the affected area, resulting in postoperative swelling. Extensive lymph node removal during cancer surgery is also linked to lymphedema and impaired drainage.25
Orthopaedic damage
Fractures or joint injuries can directly harm localised lymphatic vessels or modify limb mobility, both of which aid lymphatic flow.26 This contributes to swelling and oedema, hindering the body's ability to heal and function.
Burns
Burns destroy lymphatic capillaries and vessels in the epidermis, resulting in an accumulation of protein and fluid (lymphedema).27 Ineffective drainage promotes inflammation and infection, impeding the healing of burns.
Acute trauma
Contusions and severe contusions can cause the perforation of lymphatic vessels and lymph nodes, compromising drainage capacity. This results in prolonged inflammation of damaged tissues.28
Radiation treatment
Radiation influences the dividing lymphatic endothelial cells, resulting in vessel occlusion and fibrosis that reduces lymph transport and contributes to chronic oedema.29
Physical trauma resulting from surgery, accidents, or treatments such as radiation can cause changes in the lymphatic architecture, thereby contributing to acute and chronic oedema. Facilitating lymphatic flow and drainage is essential for healing.
Conclusion
The lymphatic system is a true unsung hero - it filters interstitial fluid, transports immune cells, and maintains our health. It becomes vitally important when disease, injury, or immobility prevent the body from performing these essential functions. Understanding the functions of the lymphatic system enhances our comprehension of how oedema develops and why discharge is crucial for recovery after trauma. Maintaining the optimal condition of this often-overlooked system is necessary to prevent swelling, combat infection, and promote wound healing.
References
- Yousef M, Silva D, Chacra NB, Davies N, Löbenberg R. The Lymphatic System: A Sometimes-Forgotten Compartment in Pharmaceutical Sciences. J Pharm Pharm Sci. 2021 Oct 22;24:533–47.
- Zuther JE. Lymphedema management : the comprehensive guide for practioners. No Title [Internet]. [cited 2023 Sep 5]; Available from: https://cir.nii.ac.jp/crid/1130000794867387136
- Rasmussen JC, Tan IC, Marshall MV, Adams KE, Kwon S, Fife CE, et al. Human Lymphatic Architecture and Dynamic Transport Imaged Using Near-infrared Fluorescence. Transl Oncol. 2010 Dec 1;3(6):362-IN7.
- Louveau A, Harris TH, Kipnis J. Revisiting the concept of CNS immune privilege. Trends Immunol. 2015 Oct;36(10):569–77.
- Clement CC, Rotzschke O, Santambrogio L. The lymph as a pool of self-antigens. Trends Immunol. 2011 Jan 1;32(1):6–11.
- Samara P, Athanasopoulos M, Athanasopoulos I. Unveiling the Enigmatic Adenoids and Tonsils: Exploring Immunology, Physiology, Microbiome Dynamics, and the Transformative Power of Surgery. Microorganisms. 2023 Jul;11(7):1624.
- Al-Suhaimi EA, Aljafary MA, Alkhulaifi FM, Aldossary HA, Alshammari T, AL-Qaaneh A, et al. Thymus Gland: A Double Edge Sword for Coronaviruses. Vaccines. 2021 Oct;9(10):1119.
- Mebius RE, Kraal G. Structure and function of the spleen. Nat Rev Immunol. 2005 Aug;5(8):606–16.
- Robey PG. Chapter 15 - Skeletal Stem Cells/Bone Marrow Stromal Cells. In: Thakker RV, Whyte MP, Eisman JA, Igarashi T, editors. Genetics of Bone Biology and Skeletal Disease (Second Edition) [Internet]. Academic Press; 2018 [cited 2023 Sep 7]. p. 241–60. Available from: https://www.sciencedirect.com/science/article/pii/B9780128041826000150
- Breslin JW, Yang Y, Scallan JP, Sweat RS, Adderley SP, Murfee WL. Lymphatic Vessel Network Structure and Physiology. In: Comprehensive Physiology [Internet]. John Wiley & Sons, Ltd; 2018 [cited 2023 Sep 7]. p. 207–99. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1002/cphy.c180015
- Swartz MA. The physiology of the lymphatic system. Adv Drug Deliv Rev. 2001 Aug 23;50(1):3–20.
- Levick JR, Michel CC. Microvascular fluid exchange and the revised Starling principle. Cardiovasc Res. 2010 Jul 15;87(2):198–210.
- Lund AW, Medler TR, Leachman SA, Coussens LM. Lymphatic Vessels, Inflammation, and Immunity in Skin Cancer. Cancer Discov. 2016 Jan 7;6(1):22–35.
- Mebius RE, Miyamoto T, Christensen J, Domen J, Cupedo T, Weissman IL, et al. The Fetal Liver Counterpart of Adult Common Lymphoid Progenitors Gives Rise to All Lymphoid Lineages, CD45+CD4+CD3− Cells, As Well As Macrophages1. J Immunol. 2001 Jun 1;166(11):6593–601.
- Alitalo K. The lymphatic vasculature in disease. Nat Med. 2011 Nov;17(11):1371–80.
- Sørensen KK, McCourt P, Berg T, Crossley C, Couteur DL, Wake K, et al. The scavenger endothelial cell: a new player in homeostasis and immunity. Am J Physiol-Regul Integr Comp Physiol. 2012 Dec 15;303(12):R1217–30.
- Füller J, Guderian D, Köhler C, Schneider A, Wendt TG. Lymph Edema of the Lower Extremities after Lymphadenectomy and Radiotherapy for Cervical Cancer. Strahlenther Onkol. 2008 Apr 1;184(4):206–11.
- Amore M, Tapia L, Mercado D, Pattarone G, Ciucci J. Lymphedema: A General Outline of Its Anatomical Base. J Reconstr Microsurg. 2016 Jan;32(1):2–9.
- Shih YCT, Xu Y, Cormier JN, Giordano S, Ridner SH, Buchholz TA, et al. Incidence, Treatment Costs, and Complications of Lymphedema After Breast Cancer Among Women of Working Age: A 2-Year Follow-Up Study. J Clin Oncol. 2009 Apr 20;27(12):2007–14.
- Zaleska M, Olszewski WL, Durlik M. The Effectiveness of Intermittent Pneumatic Compression in Long-Term Therapy of Lymphedema of Lower Limbs. Lymphat Res Biol. 2014 Jun;12(2):103–9.
- Boccardo F, Casabona F, DeCian F, Friedman D, Murelli F, Puglisi M, et al. Lymphatic Microsurgical Preventing Healing Approach (LYMPHA) for primary surgical prevention of breast cancer-related lymphedema: Over 4 years follow-up. Microsurgery. 2014;34(6):421–4.
- Moseley AL, Piller N, Carati C. THE EFFECT OF GENTLE ARM EXERCISE AND DEEP BREATHING ON SECONDARY ARM LYMPHEDEMA. Lymphology [Internet]. 2005 Aug 22 [cited 2023 Sep 6];38(3). Available from: http://journals.librarypublishing.arizona.edu/lymph/article/id/3541/
- Morgan PA, Murray S, Moffatt CJ, Honnor A. The challenges of managing complex lymphoedema/chronic oedema in the UK and Canada. Int Wound J. 2012;9(1):54–69.
- Leak LV, Burke JF. Fine structure of the lymphatic capillary and the adjoining connective tissue area. Am J Anat. 1966;118(3):785–809.
- DiSipio T, Rye S, Newman B, Hayes S. Incidence of unilateral arm lymphoedema after breast cancer: a systematic review and meta-analysis. Lancet Oncol. 2013 May 1;14(6):500–15.
- Weniger FG, Calvert JW, Newton ED. Liposuction of the Legs and Ankles: A Review of the Literature. Plast Reconstr Surg. 2004 May;113(6):1771.
- Schneider JC, Holavanahalli R, Helm P, O’Neil C, Goldstein R, Kowalske K. Contractures in Burn Injury Part II: Investigating Joints of the Hand. J Burn Care Res. 2008 Jul 1;29(4):606–13.
- Kasten KR, Goetzman HS, Reid MR, Rasper AM, Adediran SG, Robinson CT, et al. Divergent adaptive and innate immunological responses are observed in humans following blunt trauma. BMC Immunol. 2010 Jan 25;11(1):4.
- Avraham T, Yan A, Zampell JC, Daluvoy SV, Haimovitz-Friedman A, Cordeiro AP, et al. Radiation therapy causes loss of dermal lymphatic vessels and interferes with lymphatic function by TGF-β1-mediated tissue fibrosis. Am J Physiol-Cell Physiol. 2010 Sep;299(3):C589–605.
