up:: [[List of Systems of the Human Body]] tags:: #on/physiology #on/anatomy #on/immunity # Lymphatic System The lymphatic system, also known as the lymphoid system, is an integral part of the vertebrate immune system, functioning alongside the [[Circulatory System]]. It comprises a vast network of lymphatic vessels, lymph nodes, lymphoid organs, tissues, and lymph fluid. Lymph, a clear fluid, is transported by lymphatic vessels back to the heart for recirculation. Unlike the closed circulatory system, the *lymphatic system is open, playing a crucial role in returning excess fluid from tissues to the bloodstream*, as well as in immune defense. **Key points:** - The lymphatic system consists of lymphatic vessels, nodes, organs, and tissues, all contributing to immune function. - Lymph, similar to blood plasma, *carries waste products, cellular debris, bacteria, and proteins*. [[Lymphocytes]], primarily produced in lymphoid organs like the bone marrow and thymus, play a vital role in immune response. - Lymphatic vessels *collect interstitial fluid from tissues, filtering it through lymph nodes to remove unwanted materials* before returning it to circulation. - The primary lymphoid organs, such as the [[Bone Marrow]] and [[Thymus]], generate lymphocytes, while secondary lymphoid organs like [[Lymph Nodes]] and the [[Spleen]] maintain and activate these cells in response to antigens. - The *spleen acts as a blood filter, producing immune cells and antibodies*, while the *thymus matures T lymphocytes* critical for immune defense. - Lymph nodes are distributed throughout the body, filtering lymph and facilitating immune responses to pathogens. - [[Tertiary Lymphoid Organs]], formed in response to chronic inflammation, have implications in cancer immunity and immunotherapy. - Lymphoid tissue associated with the lymphatic system defends against infections and tumor spread, with structured lymph nodes and less organized mucosa-associated lymphoid tissue (MALT). - Lymphatic vessels, including capillaries and larger collecting ducts, maintain fluid balance and transport lymph, fats, and immune cells throughout the body. - The development of lymphatic tissues begins early in embryonic development, originating from lymph sacs derived from developing veins. - Functions of the lymphatic system include *interstitial fluid removal, fatty acid absorption, transportation of immune cells, and antigen presentation*. The lymphatic system serves several crucial functions in the body. It acts as a *drainage system, transporting excess fluid, proteins, and waste products from tissues back into the bloodstream*. Additionally, it plays a major role in the body's [[Immune System]], serving as the primary site for cells related to the [[Adaptive Immune System]] response, such as T-cells and B-cells. When antigens are detected, an immunological cascade is initiated, involving the activation and recruitment of various immune cells, production of antibodies and cytokines, and engagement of other immunological mechanisms. One significant aspect of the lymphatic system is its involvement in cancer. Understanding the lymphatic drainage of organs is essential for diagnosing, prognosing, and treating cancer. The system's close proximity to *various tissues allows it to transport cancerous cells between different parts of the body, facilitating metastasis*. Enlarged lymph nodes, termed [[Lymphadenopathy]], can indicate a reactive response to infection or inflammation. However, generalized lymphadenopathy may suggest more serious underlying conditions, including infections such as tuberculosis or HIV, connective tissue diseases, or cancers. [[Lymphedema]], characterized by swelling due to lymph accumulation, can occur if the lymphatic system is damaged or has malformations. ### Lymphoma Cancer of the lymphatic system itself can be primary or secondary. Hodgkin lymphoma and non-Hodgkin lymphoma are two main types, each with distinct characteristics and treatment approaches. Hodgkin lymphoma is marked by Reed-Sternberg cells and often associated with past Epstein-Barr virus infection, while non-Hodgkin lymphoma involves increased proliferation of B-cells or T-cells and typically affects older individuals. Various other diseases and conditions, such as lymphangiosarcoma, lymphangioma, and lymphangioleiomyomatosis, also affect the lymphatic system. **Key Points:** - The lymphatic system serves essential functions including fluid balance and immune response. - It plays a crucial role in cancer metastasis and can be affected by various diseases such as lymphedema and lymphoma. ### Tertiary Lymphoid Organs [[Tertiary Lymphoid Organs]] (TLOs) are highlighted as important components of disease immunity, particularly in cancer tissues. Studies emphasize the role of TLOs in promoting or impairing responses to cancer immunotherapy. Additionally, the discovery of lymphatic vessels within the central nervous system, challenging previous assumptions and offering new insights into neuroimmunology and diseases associated with immune dysfunction. **Key points:** - Tertiary lymphoid organs (TLOs) play a crucial role in disease immunity, particularly in cancer tissues. - The presence of TLOs can influence responses to cancer immunotherapy, either promoting or impairing effectiveness. - The discovery of lymphatic vessels within the central nervous system challenges previous assumptions and provides new insights into neuroimmunology. > Lymphatic system. (2024, February 8). In _Wikipedia_. https://en.wikipedia.org/wiki/Lymphatic_system