HP-C21Notes-The Lymphatic and Immune System.doc - Human Physiology Notes Chapter 21 – The Lymphatic and Immune System Functions of the Lymphatic

HP-C21Notes-The Lymphatic and Immune System.doc - Human...

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Human Physiology Notes Chapter 21 – The Lymphatic and Immune System Functions of the Lymphatic System Vessels, cells, and organs that carry excess fluids to the bloodstream o Fluid leaks from the vessels into the interstitial spaces between cells due to capillary filtration o Most of this fluid can be reabsorbed by the vessels o The remaining fluid is returned to the vessels by the lymph system Pathogens can encounter immune system cells in lymph nodes Overview of the Immune System Immune system is body’s defense mechanism o Protects against bacteria, viruses, fungi, protozoans, and parasites o Removes dead or damaged cells o Recognizes and removes abnormal cells (i.e. cancer cells) Immunity grouped into – innate (non-specific) and adaptive or acquired (specific) Anatomy of the Immune System Lymphoid Tissues Two primary lymphoid tissues = thymus gland and red bone marrow o Site for formation and maturation of immune system cells o Bone marrow Red marrow of flat bones, cancellous bone at the proximal end of long bones is site for hematopoiesis, or production of blood cells o Thymus Located below thyroid gland Contains T cells that can supply other tissues T cells can be depleted (AIDS, chemotherapy), these can only be replenished up to late childhood. After that time, repopulation of T cells must be accomplished by the secondary lymphoid organs Secondary lymphoid organs o Sites where mature immune system cells interact with pathogens and initiate an immune response o Include lymph nodes, spleen, tonsils, Peyer’s patches in intestinal mucosa (MALT) o Lymphocytes migrate constantly through blood and lymph from one lymphoid organ to another o Spleen Largest lymphoid organ Filter blood removing pathogens and old red blood cells o Lymph nodes Lymph vessels collect interstitial fluid from the tissues and send fluid to lymph nodes lymph –interstitial fluid that has reached the lymph vessels and will move to venous circulation Lymph nodes contain immune system cells that destroy foreign invaders Leukocytes (White Blood Cells or WBCs) Primary cells of immune system o Circulate in blood o Also function extravascularly in tissues A microliter of blood = 5 million RBCs, but only about 7000 WBCs Morphological groupings for WBCs – Granular cells vs agranular cells o Granulocytes – WBCs whose cytoplasmic inclusions give them a granular appearance Eosinophils Fight parasites Contribute to allergic reactions Basophils and related Mast cells (in tissues) Both release chemical inflammatory mediators (histamines and other chemicals) Neutrophils Phagocytic cells that “eat” bacteria and release cytokines o Agranular WBCs Monocytes and macrophages Primary phagocytic scavengers within tissues 1
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Serve as antigen-presenting cells in acquired immune response Lymphocytes (and plasma cells) Mediate acquired immune response Most in lymphoid tissues T and B cells
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  • Fall '16
  • Dusti Sloan

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