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22-1
Anatomy and Physiology, Sixth Edition
Rod R. SeeleyIdaho State UniversityTrent D. StephensIdaho State UniversityPhilip TatePhoenix College
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
Chapter 22Chapter 22Lecture OutlineLecture Outline**
22-3
Lymphatic System
• Lymph• Lymphatic vessels• Lymphatic tissue• Lymphatic nodules• Lymph nodes• Tonsils• Spleen• Thymus
22-4
Functions of the Lymphatic System• Fluid balance
– Excess interstitial fluid enters lymphatic capillaries and becomes lymph
• Fat absorption– Absorption of fat and other substances from
digestive tract• Defense
– Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by spleen
22-5
Lymphatic Vessels
• Carry lymph away from tissues• Lymphatic capillaries
– More permeable than blood capillaries– Epithelium functions as series of one-way valves
22-6
Lymphatic Vessels• Lymphatic capillaries join to form• Lymphatic vessels
– Have valves that ensure one-way flow• Lymph nodes: Distributed along vessels and
filter lymph• Lymphatic trunks: Jugular, subclavian,
bronchomediastinal, intestinal, lumbar • Lymphatic ducts: Right and thoracic which
connect to large veins
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Lymphatic Tissue and Nodules
• Lymphatic tissue– Consists mainly of
lymphocytes– Encapsulated or not
• Lymphatic nodules– Numerous in loose
connective tissue of digestive (Peyer’s patches), respiratory, urinary, reproductive systems
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Tonsils
• Large groups of lymphatic nodules in nasopharynx and oral cavity
• Provide protection against bacteria and other harmful material
• Groups– Palatine– Pharyngeal– Lingual
22-10
Lymph Nodes
• Organized in cortex and medulla• Substances removed by phagocytosis or stimulate lymphocytes or
both• Only structures to filter lymph
– Afferent and efferent vessels
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Spleen• Located in left superior side of abdomen
– Can be ruptured in traumatic abdominal injuries resulting in bleeding, shock, death
• Blood flows through at 3 different rates– Fast (most), slow, intermediate
• Functions– Destroys defective RBCs– Detects and responds to foreign substances– Limited reservoir for blood
22-13
Thymus
• Located in superior mediastinum• Divisions: Cortex and medulla• Site of maturation of T cells
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Immunity• Ability to resist damage from foreign substances as
microorganisms and harmful chemicals• Categories
– Innate or nonspecific resistance• Mechanical mechanisms: Prevent entry or remove microbes• Chemical mediators: Promote phagocytosis and inflammation• Cells: Involved in phagocytosis and production of chemicals
– Adaptive or specific immunity• Specificity: Ability to recognize a particular substance• Memory: Ability to remember previous encounters with a
particular substance and respond rapidly
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Mechanical Mechanisms andChemical Mediators
• Mechanical Mechanisms– Skin, tears, saliva, mucous
membranes, mucus
• Chemical Mediators– Complement
• Group of 20 proteins• Circulate in blood in
inactive form• Become activated in
cascade form: Classical or alternative pathway
– Interferons• Prevent viral replication
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Innate Immunity: Cells• White blood cells
– Most important cellular components of immune system
– Methods• Chemotaxis• Phagocytosis
• Neutrophils– Phagocytic and first
cells to enter infected tissue
• Macrophages– Monocytes that leave
blood, enter tissues– Large phagocytic cells
• Basophils and mast cells– Promote inflammation
• Eosinophils– Reduce inflammation
• Natural killer cells– Lyse tumor and virus-
infected cells
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Inflammatory Response• Tissue injury regardless of type can cause
inflammation• Response initiated by chemical mediators that
produce vasodilation, chemotactic attraction, increased vascular permeability
• Types– Local: Symptoms are redness, heat, swelling, pain, loss of
function– Systemic: Symptoms are increase in neutrophil numbers,
fever and shock
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Adaptive Immunity
• Involves the ability to recognize, respond to, and remember a particular substance
• Stimulants– Antigens: Large molecules
• Foreign: Not produced by body, introduced from outside• Self-antigens: Produced by body
– Haptens: Small molecules and capable of combining• Types
– Humoral or Antibody-mediated: B cells– Cell-mediated: T cells
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Origin and Developmentof Lymphocytes
• B and T cells– Originate in red bone
marrow– Move to lymphatic
tissue from processing sites and continually circulate
– Clones are small groups of identical lymphocytes
22-22
Origin and Developmentof Lymphocytes
• Positive selection– Ensures survival of lymphocytes that react against
antigens
• Negative selection– Eliminates lymphocytes that react against self-antigens
• Primary lymphatic organs (red bone marrow, thymus)
– Where lymphocytes mature into functional cells
• Secondary lymphatic organs– Where lymphocytes produce an immune response
22-23
Antigenic Determinants
• Antigenic determinants – Specific regions of a
given antigen recognized by a lymphocyte
• Antigenic receptors– Surface of lymphocyte
that combines with antigenic determinant
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Major Histocompatability Complex (MHC)
• Most lymphocyte activation involves glycoproteins of cell surfaces called MHC molecules– Class I molecules display antigens on surface of
nucleated cells, resulting in destruction of cells– Class II molecules display antigens on surface
of antigen-presenting cells, resulting in activation of immune cells
22-29
Lymphocyte Inhibition
• Tolerance: To prevent the immune system from responding to self-antigens– Provoked by
• Deletion of self-reactive lymphocytes• Preventing activation of lymphocytes• Activation of suppressor T cells
22-30
Antibody-Mediated Immunity
• Antibodies or Immunoglobulins (Ig)– Classes: IgG, IgM,
IgA, IgE, IgD– Structure
• Variable region: Part that combines with anitgenic determinant of antigen
• Constant region: Responsible for activities
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Cell-Mediated Immunity
• Antigen activates effector T cells and produces memory T cells• Cytotoxic T cells lyse virus-infected cells, tumor cells, and
tissue transplants• Cytotoxic T cells produce cytokines, which promote
phagocytosis and inflammation
22-35
Acquired Immunity
• Active natural immunity– Results from natural exposure to an antigen
• Active artificial immunity– Results from deliberate exposure to an antigen
• Passive natural immunity– Results from transfer of antibodies from a mother to
her fetus or baby
• Passive artificial immunity– Results from transfer of antibodies (or cells) from an
immune animal to a nonimmune one
22-37
Effects of Aging
• Little effect on lymphatic system• Decreased ability of helper T cells to
proliferate in response to antigens• Decreased primary and secondary antibody
responses• Decreased ability of cell-mediated
immunity to resist intracellular pathogens
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