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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 22

Lecture OutlineLecture Outline**

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Chapter 22

Lymphatic System and Immunity

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Lymphatic System

• Lymph• Lymphatic vessels• Lymphatic tissue• Lymphatic nodules• Lymph nodes• Tonsils• Spleen• Thymus

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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

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Lymphatic Vessels

• Carry lymph away from tissues• Lymphatic capillaries

– More permeable than blood capillaries

– Epithelium functions as series of one-way valves

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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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Lymph Drainage Into 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

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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

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Spleen

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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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Complement Cascade

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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

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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

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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

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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

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Antigen Processing

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Costimulation

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Proliferation of Helper T Cells

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Proliferation of B Cells

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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

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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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Actions of Antibodies

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Antibody Production

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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

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Interactions and Responses ofInnate and Adaptive Immunity

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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

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Ways to Acquire Adaptive Immunity

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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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Immune System Problems

• Hypersensitivity reactions

• Autoimmune disease

• Severe combined immunodeficiency disease (SCID)

• Transplantation– Acute rejection– Chronic rejection