Immune Cells and Organs | Spleen

SPLEEN

  1. The spleen is the maior site of immune responses to blood,-borne antigens.
  2.  It is a large, ovoid secondary lymphoid organ situated high in the left abdominal cavity.
  3. While lymph nodes are specialized for trapping antigen from local tissues, the spleen specializes in filtering blood and trapping blood-borne antigens; thus, it can respond
    to systemic infections.
  4. Unlike the lymph nodes, the spleen is not supplied by lymphatic vessels. Instead, blood borne antigens and lymphocytes are carried into the spleen through the splenic artery. 


    spleen-microbiologywiki

     Structure    

    • The spleen is surrounded by a capsule that extends a number of projections (trabeculae) into the interior to form a compartmentalized structure.
    • The compartments are of two types,            
    1.           The red pulp 
    2.           The white pulp
    • which are separated by a diffuse marginal zone.
    • The spleen, an organ weighing about 1509 in adults .
    • The splenic red pulp consists of a network of sinusoids populated by macrophages and numerous red blood cells (erythrocytes) and few lymphocytes; it is the site where old and defective red blood cells are destroyed and removed.Many of the macrophages within the red pulp contain engulfed red blood cells or iron pigments from degraded hemoglobin.
    • The splenic white pulp surrounds the branches of the splenic artery, forming a  periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes.
    • The marginal zone, located peripheral to the PALS, is populated by lymphocytes and macrophages. 

    Mechanism

          Blood-borne antigens and lymphocytes enter the spleen through the splenic artery, which empties into the marginal zone. In the marginal zone, antigen is trapped by interdigitating dendritic cells, which carry it to the PALS. Lymphocytes
    in the blood also enter sinuses in the marginal zone and migrate to the PALS.   

        

    Function

         The spleen is the maior site of immune responses to blood,-borne antigens.

    Reference  

    •    Kuby Immunology

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