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Chapter 22 - Overview of the Lymphoid System

Chapter 22 - Overview of the Lymphoid System - Chapter 22...

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Chapter 22 - Overview of the Lymphoid System Pathogens are microscopic organisms that cause disease; each attacks in a specific way  Viruses, Bacteria, Fungi & Parasites Lymphoid System protects us against disease; cells respond to: environmental pathogens, toxins & abnormal body cells, such  as cancers  Specific Defenses : lymphocytes; part of immune response; identify, attack & develop immunity to a specific pathogen The Immune System 0. Immunity - the ability to resist infection and disease  1. All body cells and tissues involved in production of immunity, not just lymphoid system  Nonspecific Defenses block/attack any potential infectious organism but can’t distinguish  Organization of the Lymphoid System i. Lymph - a fluid similar to plasma but does not have plasma proteins ii. Lymphatic vessels (lymphatics) - carries lymph from peripheral tissues to venous system iii. Lymphoid tissues and lymphoid organs iv. Lymphocytes, phagocytes, and other immune system cells Function of the Lymphoid System - to produce, maintain & distribute lymphocytes Structures of Body Defenses: Lymphocyte Production Lymphocytes are produced in lymphoid tissues (tonsils), lymphoid organs (spleen, thymus) & in red bone marrow;  Lymphocyte detects problems by traveling into site of injury/infection Lymphocytes circulates blood (capillaries) interstitial fluid  venous blood (lymph vessels) Lymph = interstitial fluid that has entered a lymphatic Circulation of Fluids blood   lymph & back transports hormones, nutrients & waste products Lymphatic Vessels: vessels that carry lymph; lymphoid system starts with smallest vessels Lymphatic capillaries: they differ from blood capillaries in 4 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 1-way valve & allows fluids, solutes,  viruses & bacteria to enter & prevents their return  Lymph flows from lymph capillaries to larger vessels containing 1-way valves; they travel with veins Lacteals are special lymphatic capillaries in small intestine; transport lipids from digestive tract Lymphatic vessels are in skin, mucous membranes & serous membranes lining body cavities  Smaller lymphatics join to form large lymphatic trunks that empty into 2 major collecting vessels:  0. thoracic duct  – empties into left subclavian vein 1.
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