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StructureandFunctionofLymphNodesandSpleen - BIO/MI494G...

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BIO/MI494G STRUCTURE AND FUNCTION OF LYMPH NODES AND SPLEEN FALL 2008 I. Lymph nodes 1. Location 2. Structure a. Cortex b. Paracortex c. Medulla d. Primary Follicles/Germinal Centers e. Locations of T-cells, B-cells, Macrophages and Dendritic Cells 3. Lymphatics a. Afferent Vessels b. Efferent Vessels c. Cortical and Medullary Sinuses 4. Blood Supply a. Lymphatic Artery and Vein b. Post Capillary Venules c. High Endothelial Cells 5. Lymphocyte Trafficking (recirculation and homing) a. Homing Receptors b. Vascular Addressins c. Mechanisms 1. Homing 2. Rolling 3. Activation 4. Shape change 5. Diapedesis (extravastion) 6. Lymphatic System a. Lymphatic Vessels b. Lymph c. Lymphatic Flow d. Function 7. Function II. Spleen 1. Location 2. Structure a. Red Pulp b. White Pulp 3. White pulp a. Marginal Zone b. Marginal c. Sinus d. Follicle (Germinal Center) B-Cell Rich 1. B-Cell Rich e. Periateriolar Lymphoid Sheath (PALS) 1. T-cell Rich 4. Function
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afferent lymphatic vessel T-cell area germinal center Figure 1.10 Architecture of the lymph node, the site where blood-borne lymphocytes respond to lymph-borne pathogens. Human lymph nodes are small kidney-shaped organs weighing 1 gram or less that form junctions where a number of afferent lymph vessels bringing lymph from the tissues unite to form a single, larger efferent lymph vessel. The lymph node is packed with lymphocytes, macrophages and other cells of the immune system through which the lymph percolates. In a lymph node, pathogens are removed from the lymph by macrophages, then degraded and used to stimulate lymphocytes. Lymphocytes arrive at lymph nodes in the arterial blood. They enter the node by passing between the endothelial cells that line the fine capillaries within the lymph node (not shown). The lymphoid follicle (mostly B cells) medullary sinus artery vein efferent lymphatic vessel marginal sinus ~'- population of lymphocytes within a node is in a continual state of flux, with new lymphocytes entering frofl] the blood while others leave in the efferent lymph. Within the lymph node there are anatomically discrete areas where B or T cells tend to congre- gate. A lymph node draining a site of infection increases in size owing to the proliferation of activated lymphocytes, a phenome- non sometimes referred to as 'swollen glands'. The expansion of lymphocyte populations takes place in spherical lymphoid follicles present in the lymph node cortex. As lymphocyte. division and differentiation proceeds, the follicle morphology changes and it is then called a germinal center. The photograph shows a section through a lymph node in which there are promi- nent germinal centers. Photograph (x 7) courtesy of N. Rooney. adenoid
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StructureandFunctionofLymphNodesandSpleen - BIO/MI494G...

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