lymphatic system

(noun)

In mammals, including humans, a network of lymph vessels and lymph nodes that transport fluid, fats, proteins, and lymphocytes to the bloodstream as lymph, and remove microorganisms and other debris from tissues.

Related Terms

Examples of lymphatic system in the following topics:

  • Structure of the Lymphatic System

    • The lymphatic system consists of lymphatic vessels and associated lymphoid organs.
    • The lymphatic system is a collection of structures and vessels that drains lymph from blood and has several other functions.
    • It is a circulatory system for lymph fluid and the site of many key immune system functions.
    • The lymphatic vessels are the lymphatic system equivalent of the blood vessels of the circulatory system and drain fluid from the circulatory system.
    • The lymphatic system is an active pumping system driven by segments that have a function similar to peristalsis.

  • Functions of the Lymphatic System

    • The lymphatic system is the site of many key immune system functions.
    • It is important to distinguish that immune system functions can happen almost anywhere in the body, while the lymphatic system is its own system where many immune system functions take place.
    • Besides immune system function, the lymphatic system has many functions of its own.
    • The lymphatic system also facilitates fatty acid absorption from the digestive system.
    • In addition to tissue fluid homeostasis, the lymphatic system serves as a conduit for transport of cells involved in immune system function.

  • Distribution of Lymphatic Vessels

    • The lymphatic system comprises a network of conduits called lymphatic vessels that carry lymph unidirectionally towards the heart.
    • The lymphatic system is a circulatory system for lymphatic fluid, comprising a network of conduits called lymphatic vessels that carry the fluid in one direction toward the heart.
    • The lymphatic system is composed of many different types of lymph vessels over a wide distribution throughout the body.
    • That means the lymphatic system is an open system with linear flow, while the cardiovascular system is a closed system with true circular flow.
    • Describe the structure of the lymphatic system and its role in the immune system and blood circulation

  • Cardiovascular and Lymphatic System Defenses

    • The circulatory system has a defence against microbial invaders in the form of the lymphatic system.
    • The cardiovascular and lymphatic are both integral parts of the circulatory system.
    • While the lymphatic system is part of the circulatory system, comprising a network of conduits called lymphatic vessels.
    • Lymphatic organs play an important part in the immune system, having a considerable overlap with the lymphoid system.
    • The lymphatic system may therefore contribute to the spread of cancer.

  • Cytotoxic T Lymphocytes and Mucosal Surfaces

    • The lymphatic system houses large populations of immune cells which are released upon detection of a pathogen.
    • Lymph moves about the body through the lymphatic system, which is made up of vessels, lymph ducts, lymph glands, and organs such as tonsils, adenoids, thymus, and spleen.
    • Cells of the immune system can travel between the distinct lymphatic and blood circulatory systems, which are separated by interstitial space, by a process called extravasation (passing through to surrounding tissue).
    • (a) Lymphatic vessels carry a clear fluid called lymph throughout the body.
    • Describe the features of the lymphatic system as they relate to the immune response

  • Lymph Trunks and Ducts

    • After filtration by the lymph nodes, efferent lymphatic vessels take lymph to the end of the lymphatic system.
    • The final goal of the lymphatic system is to recirculate lymph back into the plasma of the bloodstream.
    • There are two specialized lymphatic structures at the end of the lymphatic system, called the lymph trunks and ducts.
    • Lymphatic trunks then drain lymph fluid into the lymph ducts, the final part of the lymphatic system.
    • This point marks the end of lymph fluid's journey through the lymphatic system.

  • Metastasis Through Lymphatic Vessels

    • Some cancer cells acquire the ability to penetrate the walls of lymphatic and/or blood vessels, after which they are able to circulate through the bloodstream (circulating tumor cells) to other sites and tissues in the body.
    • This process is known as a lymphatic or hematogeneous spread.
    • Metastasis is a complex series of steps in which cancer cells leave the original tumor site and migrate to other parts of the body via the bloodstream or the lymphatic system.
    • By degrading the ECM, which acts as a barrier to adjoining tissue, cancer cells are able to breach the ECM and enter the lymphatic system.
    • Lymphatic spread: Invasion into the lymphatic system allows the transport of tumor cells to regional and distant lymph nodes and, ultimately, to other parts of the body.

  • Lymphatic Vessel Structure

    • The general structure of lymphatic vessels is similar to that of blood vessels since these are the only two types of vessels in the body.
    • The smallest vessels, such as the lymphatic capillaries, may have no outer adventitia.
    • Valves are found in larger lymph vessels and collecting vessels and are absent in the lymphatic capillaries.
    • A lymphangion is the term for the space between two semilunar valves in a lymphatic vessel, functional unit of the lymphatic system.
    • Without valves, the lymphatic system would be unable to function without a central pump.

  • Lymphoid Tissue

    • The tissues of lymphoid organs are different than the tissues in most other organ systems in that they vary considerably based on cell cycle proliferation of lymphocytes.
    • Lymphatic tissue begins to develop by the end of the fifth week of embryonic development.
    • Lymphatic vessels develop from lymph sacs that arise from developing veins, which are derived from mesoderm, the inner tissue layer of the embryo.
    • Development of lymphatic tissue starts when venous endothelial tissues differentiate into lymphatic endothelial tissues.
    • Smaller lymph vessels and lymphatic capillaries develop after that until the lymphatic system is completed at the closed end of each lymphatic capillary.

  • Lymphatic Capillaries

    • Lymphatic circulation begins in the smallest type of lymph vessels, the lymph capillaries.
    • Unlike larger lymphatic vessels, lymphatic capillaries do not contain smooth muscle nor do they have a well developed adventitia, only small elastic filaments that perform a similar function.
    • During lymph vessel obstruction (such as through elephantiasis infection), lymph will be unable to progress normally through the lymphatic system, and pressure within the blocked off lymph capillaries increases to the point where backflow into tissues may occur, while the pressure of interstitial fluid gradually rises.
    • The lymphatic capillaries bring lymph further into the lymphatic vessels.
    • This moves lymph further along the system despite the fall in pressure that occurs when moving from the higher-pressure capillaries to the lower-pressure collecting vessels.