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Lecture12 lymphatic system
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2. Lymphatic organs include: - thymus - lymph nodes - spleen - tonsils - lymph nodules in the wall of intestine (lymphonoduli solitarii and lymphonoduli aggregati or Peyer's patches) and in the wall of respiratory and urinary passages ( GALT or MALT ) Thymus occupies a central position among lymphatic organs it is located behind the sternum the thymus varies in size and development with the age, being the largest around puberty - weight 15 - 17 gram
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5. i n addition, the medulla contains eosinophilic and neutrophilic granulocytes, plasma cells, and concentric corpuscles of Hassall - resemble acidophilic bodies of 50-200 m in diameter composed of concentrically arranged epithelial reticular cells that degenerate
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9. The cortex - is composed of lymph nodules (or follicles), from which many c ontain germinal centres , i n ordinary stained preparations they are lighter than the periphery of the nodule l ighter staining is due the occurrence of lymphoblasts with pale nuclei ( dispersed euchromatin )
10. t he medulla - consists of medullary cords of irregular shape that anastomose each other , sp aces between cords are occup ied with medullary sinuses
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13. Functions of the lymph nodes: l ymphopoiesis filtration of the lymph Elaboration, u tarbetande, of antibodies
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17. White pulp It consist s of reticular connective tissue and lymphocytes i t follows the arteries (called central arteries ) and forms along them periarterial lymphatic sheaths (PALS) at intervals it is thickened into ovoid bodies, called the splenic nodules (or Malpighian bodies (which may show GC)
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23. venous sinuses have irregular lumina T he venous sinuses empty into the pulp veins , which leave the pulp and unite to form trabecular veins they join up to form finally the splenic vein
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29. lymph nodules in the wall of respiratory passages (MALT)
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Editor's Notes
Germinal centres (GC) are sites within lymph nodes or lymph nodules in peripheral lymph tissues where intense mature B lymphocytes rapidly proliferate, differentiate, mutate through somatic hypermutation and class switch during antibody responses
Lymph nodes are garrisons of B , T , and other immune cells . Lymphopoiesis refers to the generation of lymphocytes
Germinal centres (GC) are sites within lymph nodes or lymph nodules in peripheral lymph tissues where intense mature B lymphocytes rapidly proliferate, differentiate, mutate through somatic hypermutation and class switch during antibody responses The splenic cords contain T and B lymphocytes. Macrophages. Plasma and other blood cells. + RETICULAR CELLS AND RETICULAR FIBERS (PHAGOCYTOTIC)
The mucosa -associated lymphoid tissue (MALT) (also called mucosa -associated lymphatic tissue) is the diffuse system of small concentrations of lymphoid tissue found in various sites of the body such as the gastrointestinal tract , thyroid , breast , lung , salivary glands , eye , and skin . MALT is populated by lymphocytes such as T cells & B cells, as well as plasma cells and macrophages, each of which is well situated to encounter antigens passing through the mucosal epithelium. In the case of intestinal MALT, M cells are also present, which sample antigen from the lumen and deliver it to the lymphoid tissue.
T-LYMPHOCYTES Cellular immunity: involves the activation of macrophages , natural killer cells (NK), antigen -specific cytotoxic T-lymphocytes , and the release of various cytokines in response to an antigen…………………………All extracellular fluid must filter through lymph nodes as it traverses the lymphatics on its way back to the systemic circulation. Antigen residing in the interstitium is thus swept to the lymph nodes for processing.
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