22_LectureOutline

22_LectureOutline - Overview of the Lymphoid System...

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Overview of the Lymphoid System Pathogens Microscopic organisms that cause disease Viruses Bacteria Fungi Parasites Each attacks in a specific way The Lymphoid System Protects us against disease Lymphoid system cells respond to Environmental pathogens Toxins Abnormal body cells, such as cancers Specific Defenses Lymphocytes Part of the immune response Identify, attack, and develop immunity: to a specific pathogen The Immune System Immunity The ability to resist infection and disease All body cells and tissues involved in production of immunity Not just lymphoid system Nonspecific Defenses Block or attack any potential infectious organism Cannot distinguish one attack from another Organization of the Lymphoid System Lymph A fluid similar to plasma but does not have plasma proteins Lymphatic vessels (lymphatics) Carries lymph from peripheral tissues to the venous system Lymphoid tissues and lymphoid organs
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Lymphocytes, phagocytes, and other immune system cells Function of the Lymphoid System To produce, maintain, and distribute lymphocytes Structures of Body Defenses Lymphocyte Production Lymphocytes are produced In lymphoid tissues (e.g., tonsils) Lymphoid organs (e.g., spleen, thymus) In red bone marrow Lymphocyte distribution Detects problems Travels into site of injury or infection Lymphocyte Circulation From blood to interstitial fluid through capillaries Returns to venous blood through lymphatic vessels Lymph = interstitial fluid that has entered a lymphatic The Circulation of Fluids From blood plasma to lymph and back to the venous system Transports hormones, nutrients, and waste products Lymphatic Vessels Are vessels that carry lymph Lymphoid system begins with smallest vessels Lymphatic capillaries (terminal lymphatics) Lymphatic Capillaries Differ from blood capillaries in four ways Start as pockets rather than tubes Have larger diameters Have thinner walls Flat or irregular in section Lymphatic Capillaries Endothelial cells loosely bound together with overlap Overlap acts as one-way valve Allows fluids, solutes, viruses, and bacteria to enter Prevents return to intercellular space Lymph Flow
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From lymphatic capillaries to larger lymphatic vessels containing one-way valves Lymphatic vessels travel with veins Lacteals Are special lymphatic capillaries in small intestine Transport lipids from digestive tract Lymphatic Vessels Superficial lymphatics Deep lymphatics Are located in Skin Mucous membranes Serous membranes lining body cavities Superficial and Deep Lymphatics The deep lymphatics Are larger vessels that accompany deep arteries and veins Superficial and deep lymphatics Join to form large lymphatic trunks Trunks empty into two major collecting vessels:
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22_LectureOutline - Overview of the Lymphoid System...

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