Describe how the thymus’s anatomy changes as we age.
Introduction:
Central lymphoid tissue comprises bone marrow and thymus. All pluripotent lymphoid stem cells are initially produced by the bone marrow, except during early fetal life when the liver and spleen have these. The central lymphoid tissue allows the stem cells to undergo differentiation so that the lymphocytes can become the competent defensive elements of the immune system. Bone marrow helps differentiate the (committed) B-lymphocytes, capable of synthesizing antibodies after being transformed into plasma cells. The thymus helps differentiate immunologically competent but uncommitted T-lymphocytes (10 percent of the thymic population), which are long-lived, join the circulating pool of lymphocytes and populate the thymus-dependent areas of lymph nodes and other peripheral lymphoid organs. T-cells are uncommitted and thus, can react with a wide variety of foreign antigenic stimuli. These respond by cytotoxic cell killing by bringing the macrophages and stimulating large mononuclear cells and the B-lymphocyte's helper activity.
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