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| {{Thymus Histology}} | | {{Thymus Histology}} |
| |} | | |} |
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| ==Thymus==
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| [[File:Thymus cartoon.jpg|thumb|Adult Thymus]]
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| [[File:Gray1178.jpg|thumb|Fetal thymus anatomy]]
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| Gross Anatomy
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| * Superior mediastinum, anterior to heart
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| * Bilobed lymphoepithelial organ
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| {|
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| | Histology
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| * Contains reticular cells but no fibers
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| * Stem lymphocytes
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| ** proliferate and differentiate
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| ** forms long-lived T- lymphocytes
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| * removes auto-reactive T-lymphocytes (negative selection)
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| | {{Thymus Movie 1}}
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| |}
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| ===Thymus Cells===
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| {|
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| |-bgcolor="F5FAFF"
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| ! Reticular cells
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| ! Macrophages
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| ! Lymphocytes
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| |-
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| * Abundant, eosinophilic, large, ovoid and light nucleus 1-2 nucleoli
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| * sheathe cortical capillaries
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| * form an epitheloid layer
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| * maintain microenvironment for development of T-lymphocytes in cortex (thymic epitheliocytes)
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| * cortex and medulla
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| * difficult to distinguish from reticular cells in {{HE}}
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| * remove auto-reactive T-lymphocytes
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| * located in cortex and medulla
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| * more numerous (denser) in cortex
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| * majority are developing T-lymphocytes (= thymic lymphocytes or thymocytes)
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| |}
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| Histology
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| <gallery>
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| File:Fetal thymus.jpg|Fetal thymus
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| File:Thymus - young 01.jpg|Young medulla
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| File:Thymus - young 02.jpg|Young cortex
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| </gallery>
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