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Unformatted text preview: Chapter 18 4/3/08 3:48 PM Lymphoid tissues – Include thymus, bone marrow, spleen and lymph nodes—all very essential to Defense System. • Blood and Lymph are fluids central to function. o Blood Plasma – yellowish solution containing ions, small molecular solutes, and soluble proteins. Red blood cells, White blood cells, and platelets. Red blood cell isolated to closed Circ. System. White blood cells and platelets are found in lymph. o Lymph – fluid derived from blood and other tissues that accumulates in intercellular spaces throughout body. Moves slowly into vessels of lymphatic system. Tiny lymph capillaries -> larger ducts that join -> one large vessel, thoracic duct -> joins major vein (left subclavian vein) near heart. Lymph eventually returned to blood and circulatory system. Lymph nodes – contain variety of white blood cells. Filters lymph and inspects for nonself materials by defensive cells • White blood cells ( See Figure 18.2) o 4 Billion RBC, 7 million WBC } all originate from pluripotent stem cells in bone marrow. o WBC have nuclei and are colorless. o WBC can leave closed circ. System and enter intercellular spaces. o Two Groups of WBC: Granular cells – include histamine producing signaling cell and phagocytes. Important phagocytes are: dendritic cells and macrophages. • These engulf nonself material and present partly digested nonself material to T cells. Lymphocytes – specific defenses against nonself or altered cells. (Virus-infected cells, or Tumor cells). 2 Types: T Cells – migrate from bone marrow via blood to Thymus to mature. • B Cells – from bone marrow to blood and lymph vessels. Produces antibodies that enter blood and bond to nonself substances. • Four Major Proteins that help in Cell-Cell interactions of Defense. o Antibodies – bind specifically to substances identified by defense system as nonself or altered-self, denaturing substance. Produced by B Cells o T Cell Receptors – integral membrane proteins on face of T Cell. Recognize and bind to nonself substances on surface of other cells. o Major histocompatability complex – protrude from surface of most cells in mammalian body. Important self-identifying labels; coordinate interactions between lymphocytes and marcrohages. o Cytokines – souble signal proteins released by T Cells, macrophages, and other cells. Bind and alter behavior of target cells. Different cytokines activate or inactivate B Cells, macrophages, and T cells. Some can kill tumor cells. Non-Specific Defenses – physical, cellular, and chemical. (STUDY Table 18.1) • Skin is primary defense against invasion. o Normal Flora – natural occupants that reproduce in great numbers without causing disease compete against pathogens for space and nutrients....
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- Spring '08
- cells, T Cells