The Lymphatic System and Lymphoma
by Robert Tallitsch, PhD | July 14, 2022
Video explanation of the lymphatic system and patient case example of lymphoma! Use this video, article, and activity in your classes!
Written by: Robert Tallitsch, PhD
The lymphatic (lymphoid) system is functionally a part of the cardiovascular system. The lymphatic system transports and monitors a fluid called lymph. Lymphatic vessels carry the lymph from the periphery to the lymphatic system, and then ultimately to the veins of the cardiovascular system. Lymph is composed of interstitial fluid, macrophages, and lymphocytes.
The functions of the lymphatic system are:
- Maintenance of normal blood volume and the elimination of variations in the local composition of the interstitial fluid.
- Provide an “alternative route” for the transport of wastes, nutrients, and hormones.
- Production and maintenance of lymphocytes.
Contrary to the vessels of the cardiovascular system, which make a complete circuit that begins and ends at the heart, lymphatic vessels only carry fluid from the periphery to the venous system. In general, lymphatic vessels are wider in diameter, thinner walled, and possess greater permeability that the vessels of the cardiovascular system.
Cells of the Lymphatic System
The cells of the lymphatic system are termed lymphocytes. These cells are responsible for specific, also referred to as acquired, immunity. This type of immunity is not inherited at birth; rather it is acquired over time following exposure to pathogens. The two types of specific immunity are artificial or natural. Artificial immunity is acquired through vaccinations, while natural immunity is acquired by everyday encounters and exposures to disease-causing agents and pathogens.
The primary cells of the immune system are termed lymphocytes. These cells are found within the lymphatic and cardiovascular systems, as well as within the interstitial spaces of the body. When a lymphocyte encounters a pathogen it will initiate an immune response.
There are three classes of lymphocytes: T cells, B cells, and NK cells. Each cell type has distinctive biochemical and functional characteristics.
T cells comprise the largest percentage of lymphocytes. These cells originate in the bone marrow, and then migrate to the thymus to become immunocompetent, or activated. When properly stimulated, T cells differentiate into several different cell types that will attack antigens and increase the body’s immune response.
B cells, which are the second most common form of lymphocytes, originate and become immunocompetent within the red bone marrow. Immunocompetent B cells divide and differentiate into either plasma cells (plasmocyctes), which secrete antibodies, or Memory B cells. Memory B cells become activated only if the antigen appears again in the body at a later date.
NK cells (also termed Natural Killer cells) attack foreign cells, normal cells infected with a virus, and cancer cells that appear within normal tissues.
Video explanation of lymphocytes: T cells, B cells, and NK cells + patient case example of lymphocytopenia!
Lymphatic Tissues and Organs
Lymphatic tissue is made up of connective tissue and lymphatic cells. Loose lymphatic tissue is composed of loosely organized lymphatic cells within the connective tissue of an organ. Although loose lymphatic tissue may occur within any organ of the body, the most common locations are the respiratory, urinary, and digestive systems.
Lymphatic organs are (a) encapsulated within a layer of connective tissue and (b) are composed of tightly organized lymphatic cells. Examples of lymphatic organs are the tonsils, thymus, spleen, and lymph nodes. We will look more closely at the anatomy of a lymph node.
Lymph nodes are small, encapsulated lymphatic organs located along the course of lymphatic vessels throughout the body. Several afferent lymph vessels enter each lymph node, and only one or two efferent lymph vessels exit the node.
The connective tissue capsule will, at various locations of the node, extend deep into the body of the lymph node, forming structures termed trabeculae. A meshwork of interconnected spaces, termed lymphatic sinuses, extend throughout the lymph node from the afferent lymphatic vessels. These lymphatic sinuses are found deep to the capsule, adjacent to the trabeculae, and throughout the remainder of the lymph node. The sinuses then coalesce and exit the node by the efferent lymphatic vessels. The lymphatic sinuses are crisscrossed with connective tissue fibers, phagocytic cells, and lymphocytes. This combination of fibers and cells filters the lymph as it passes through the node. Any foreign antigens and cells encountered by this filtration process will initiate an immune response.
Lymph nodes are widely distributed throughout the body — typically in areas that are susceptible to injury or pathogenic infiltration:
- Intestinal lymph nodes and mesenteric lymph nodes filter lymph originating within the digestive (gastrointestinal) system.
- Abdominal lymph nodes filter lymph originating from the urinary and reproductive systems.
- Popliteal lymph nodes and inguinal lymph nodes filter lymph originating in the leg and thigh of the lower limb.
- Cervical lymph nodes filter lymph originating from the head and neck.
- Axillary lymph nodes filter lymph originating from the upper limbs.
Lymphoma is a general term applying to cancers that start in the lymphatic system. There are two main types of lymphomas:
- Hodgkin’s lymphoma — which spreads in an orderly manner from one group of lymph nodes to another.
- Non-Hodgkin’s lymphoma, which spreads through the lymphatic system in a non-orderly manner.
Hodgkin’s lymphoma is most commonly seen in teens and young adults — typically between the ages of 15 to 39 — and then again in older adults (greater than 75 years-of-age).
Although the cause(s) of lymphoma is/are unknown at this time, there are some links that statistically seem to indicate a higher chance of developing lymphoma. These include:
- Family history
- Exposure to certain environmental triggers, including herbicides and pesticides
- Infection with HIV
- Certain viruses, such as human T-cell lymphotrophic virus and Epstein-Barr virus
- Exposure to high levels of ionizing radiation
The symptoms of lymphoma — be it Hodgkin’s or non-Hodgkin’s lymphoma — are quite similar to symptoms from other diseases. Symptoms include fever, night sweats, fatigue, and significant weight loss.
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Lymphoma - A general term applied to cancers originating within the lymphatic system.
NK cells - “Natural killer cell” within the lymphatic system. This cell type attacks foreign cells, cancer cells, and normal cells infected with a virus.
B cells - The second most common form of lymphocytes. These cells originate and become immunocompetent within the red bone marrow.
Lymphatic organ - Lymphatic organs are organs that are encapsulated within a layer of connective tissue and contain tightly organized lymphatic cells.
Lymphocyte - The cells of the lymphatic system that are responsible for specific, or also referred to as acquired, immunity.
Lymph nodes - Small, encapsulated lymphatic organs located along the course of the lymphatic vessels throughout the body.
Mesenteric lymph node - A lymph node that drains lymph from the digestive (gastrointestinal) system.
Loose lymphatic tissue - Loose lymphatic tissue is composed of loosely organized lymphatic cells within the connective tissue of an organ.
Hodgkin’s lymphoma - A type of lymphoma that spreads in an orderly manner from one group of lymph nodes to another.
- Lymphatic vessels differ from those of the cardiovascular system in what ways?
A: Lymphatic vessels are thinner, wider, and have a greater permeability as compared to vessels of the cardiovascular system.
- What three components comprise lymph?
A: Interstitial fluid, macrophages, and lymphocytes
- What cells are responsible for specific, or also referred to as acquired, immunity?
- What type of lymphocyte becomes immunocompetent within the thymus?
A: T cells
- What lymph nodes drain lymph originating in the leg and thigh?
A: Popliteal and inguinal lymph nodes
- What is acquired immunity?
A: The type of immunity is not inherited at birth.
- What are the two types of acquired immunity?
A: The two types of acquired immunity are artificial and natural.
- What are the age ranges that see the highest rates of Hodgkin’s lymphoma?
A: 15 to 39 and in those older than 75 years-of-age
- List the five most common links that statistically appear to indicate a higher chance of developing a lymphoma.
A: Family history, exposure to certain environmental triggers, HIV infection, certain viruses, and exposure to ionizing radiation.
- What is the difference between Hodgkin’s and non-Hodgkin’s lymphoma?
A: Hodgkin’s spreads in an orderly manner from one group of lymph nodes to the next. Non-Hodgkin’s lymphoma spreads in a non-orderly manner.
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