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Lymphoid System
Lymphoid System

Lymphoid System

Systema lymphoideum

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The lymphoid system is composed of lymphatic vessels and lymphoid organs.

The lymphatic vessels form a drainage system parallel to the cardiovascular system. It is responsible for draining interstitial (or extracellular) fluid that has escaped from the cardiovascular system, as well as the removal of cellular debris, and returning it to the venous system as lymph.

Lymphatic vessels begin as small, endothelial-lined capillaries with an incomplete basement membrane, allowing interstitial fluid and debris to enter the capillaries. Capillary networks drain defined areas of the body into lymphatic vessels, which transports lymph through lymphoid organs and return it to the venous system (Földi et al., 2012).

Lymphoid organs are part of the immune system of the body. These organs are categorized into primary and secondary lymphoid organs, which are capable of detecting and combating pathogens, malignant or degenerative cells, and foreign material present in lymph.

Primary lymphoid organs include the bone marrow and the thymus. These organs are responsible for the generation of new, or de novo, lymphocytes. B and T lymphocytes differentiate and mature in the primary lymphoid organs (Standring, 2016).

Secondary lymphoid organs, such as the spleen and lymph nodes, are the sites in which B and T lymphocytes, along with antigen-presenting cells initiate an immune response.

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Földi, M., Földi, E., Strößenreuther, R. and Kubik, S. (2012) Földi's Textbook of Lymphology: for Physicians and Lymphedema Therapists. Elsevier Health Sciences.

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series: Elsevier Limited.

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Lymphatic System

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The lymphatic system is a network of vessels and tissues composed of lymph, an extracellular fluid, and lymphoid organs, such as lymph nodes.

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