Wednesday, February 25, 2015
FUNCTIONS OF THE SPLEEN
The spleen receives a high proportion of the cardiac output which contributes to its effectiveness as a filter of blood and a site for lymphocyte recirculation and lodging. Filtration of efete cells, debris and microorganisms occurs primarily in the reticulum of the red pulp chords and in the seive-like endothelium of venous sinuses. Reticular cells provide anchoring sites for mononuclear phagocytes that perform reticuloendothelial functions in the red pulp and marginal zone. The white pulp of the spleen contains a peripheral lymphatic tissue microenvironment for antigen trapping, cellular collaboration, lymphocyte proliferation and antibody production in addition to providing young bone marrow emigrant B-cells a place to complete maturation. The spleen is the primary site for initiation of immune responses to antigens and pathogens that have invaded the blood stream in addition to being a partner in every other immune response in the body. Antigen-laden mononuclear cells and lymphoblasts, released into efferent lymph from other lymphatic tissues 48 to 100 hours after antigen priming, lodge in the spleen and set up satellite zones of T- and B-cell proliferation. During active immune responses lymphoblastic B-cells committed to plasma cell differentiation lodge in the red pulp cords and sinuses where they mature and commence secreting antibody.
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