Immune System Structure and Function

The lymphoreticular system is a complex organization of cells of diverse morphology that are distributed widely in different organs and tissues of the human body. It is responsible for immunity.

The specific immune response to antigen is of two types: humoral or antibody-mediated immunity and cell-mediated immunity.

<p>Central or primary lymphoid organs are the major sites for lymphopoiesis. They have the ability to produce progenitor cells of the lymphocytic lineage where precursor lymphocytes proliferate, develop, and differentiate from lymphoid stem cells to become immunologically competent cells. The primary lymphoid organs include thymus and bone marrow.</p> Signup and view all the answers

<p>The primary function of the thymus is the production of thymic lymphocytes. It is a major organ for proliferation of lymphocytes in the body.</p> Signup and view all the answers

<p>Bone marrow is the site for proliferation of stem cells and for the origin of pre-B cells and their maturation to become immunoglobulin-producing lymphocytes. Immature B cells proliferate and differentiate within the bone marrow.</p> Signup and view all the answers

<p>Peripheral or secondary lymphoid organs consist of lymph nodes, spleen and nonencapsulated structures such as mucosal-associated lymphoid tissues (MALT). These organs serve as the sites for interaction of mature lymphocytes with antigens.</p> Signup and view all the answers

<p>The lymph nodes act as a filter for the lymph, the fluid, and the cellular content of the lymphocytic circulatory system. They also provide sites for mingling of lymphocytes, monocytes, and dendritic cells for initiation of immune responses.</p> Signup and view all the answers

<p>The spleen is the largest lymphoid organ. It plays a major role in mounting immune responses to antigens in the blood stream. The circulating antigens are trapped by the macrophages present in the marginal zone. The spleen also filters or clears infectious organisms, aged or defectively formed elements, and particulate matter from the peripheral blood. In addition, the spleen traps blood-borne antigens and microbes.</p> Signup and view all the answers

<p>Mucosal-associated lymphoid tissues (MALT) consist of the lymphoid tissues of the intestinal tract, genitourinary tract, tracheobronchial tree, and mammary glands. All of the MALT contain both T and B lymphocytes, and the latter predominate.</p> Signup and view all the answers

<p>The lymphatic circulatory system serves as a secondary circulatory system for the body, collecting lymph, which is a clear watery fluid containing leukocytes and cellular debris, from various organs and tissues.</p> Signup and view all the answers