Thymic macrophages help clear out debris of dead and dying cells Surviving T

Thymic macrophages help clear out debris of dead and

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Thymic macrophages – help clear out debris of dead and dying cells Surviving T cells enter medulla medulla – consists of widely scattered, more mature T cells, epithelial cells, dendritic cells, and macrophages T cells that leave thymus via blood migrate to lymph nodes, spleen, and other lymphatic tissues where they colonize parts of these organs and tissues
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~ 600 lymph nodes scattered along lymphatic vessels (in superficial and deep groups) that serve as filters to trap and destroy foreign objects in lymph fluid Important group of regional lymph nodes include: Submandibular Cervical Axillary o Mediastinal o Inguinal
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Lymph nodes make immune cells that help the body fight infection Filter the lymph fluid and remove foreign material such as bacteria and cancer cells When bacteria are recognized in the lymph fluid , the lymph nodes make more infection-fighting white blood cells, which cause the nodes to swell Swollen nodes are sometimes felt in the neck, under the arms, and groin
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Contain T cells, macrophages, follicular dendritic cells, and B cells Like thymus, lymph nodes are covered by capsule (connective tissue) Capsular extensions called trabeculae divide the node into compartments, provide support, and provide a route for blood vessels into interior of node
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stroma (supporting framework) - Capsule, trabeculae, reticular fibers (inside capsule), and fibroblasts (inside capsule) parenchyma (functioning part) is divided into cortex and medulla
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Outer Cortex: B cells Follicular dendritic cells macrophages
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follicular cells “present” an antigen B cells proliferate and develop into antibody-producing plasma cells or develop into memory B cells Memory B cells “remember” having encountered a specific antigen (fight second infection faster!)
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Inner cortex Consists mainly of T cells and dendritic cells that enter lymph node Dendritic cells present antigens to T cells ( antigen- presenting cells), causing them to proliferate Newly formed T cells migrate from lymph node to areas of body where there is antigenic activity
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Medulla of lymph node Contains B cells, antibody producing plasma cells that have migrated out of cortex into medulla, and macrophages
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Lymph nodes function as a filter As lymph enters one end of a lymph node, foreign substances are trapped by reticular fibers within sinuses of node Macrophages then destroy foreign substances by phagocytosis Lymphocytes destroy others by immune responses Filtered lymph then leaves other end of lymph node
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Afferent lymphatic vessels have valves pointing inward, to keep lymph flowing in one direction Efferent have valves point out (fewer than afferent, which slows the flow through so more time to filter)
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Largest mass of lymphatic tissue in the body found in the left hypochondriac region between the fundus of the stomach and the diaphragm
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Superior surface of spleen is smooth and convex and conforms to the concave surface of the diaphragm Like lymph nodes, spleen has a hilum Through the hilum passes the splenic artery and vein, and efferent lymphatic vessels Neighboring organs make impressions
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  • Fall '16
  • Lambrini Nicopoulos
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