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The Lymphatic System, Immunity and Microbiology. Essential Knowledge. Briefly outline the major role of the thymus gland in immunity. Briefly outline the role of the spleen. List the 7 non-specific defence mechanisms and briefly describe how they work. Discuss complement activation.
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Essential Knowledge Briefly outline the major role of the thymus gland in immunity. Briefly outline the role of the spleen. List the 7 non-specific defence mechanisms and briefly describe how they work. Discuss complement activation. List and briefly describe the components of specific immunity. Differentiate between innate and acquired immunity and discuss further classification of acquired immunity.
Lymphatic System Structure and Function The lymphatic system consists of a pale yellow fluid called lymph, lymphatic vessels, lymphatic tissue and red bone marrow. Functions: 3 Primary Functions- (I) Draining excess interstitial fluid. (II) Transporting dietary lipids. (III) Carrying out Immune Responses.
Components of the Lymphatic System Figure 22.1 Tortora, G.J. & Derrickson, B. 2006. Principles of Anatomy and Physiology, 11th edition.
Lymphatic System Structure and Function Lymphatic Vessels and circulation Lymphatic capillaries Lymph trunks and Ducts Formation and flow of Lymph
Routes of Drainage and Lymphatic Capillaries Figure 22.2; Figure 22.3 Tortora, G.J. & Derrickson, B. 2006. Principles of Anatomy and Physiology, 11th edition.
Lymphatic Organs and Tissues Primary Lymphatic Organs: Red bone marrow and Thymus Secondary Lymphatic Organs: Lymph nodes, Spleen and Lymphatic nodules.
Thymus Bi-lobed organ located between the sternum and aorta. Each thymic lobule consists of an outer cortex and central medulla.
Lymph nodes Located along lymphatic vessels are about 600 bean shaped lymph nodes. Lymphatic nodules: Primary and Secondary
Spleen Largest single mass of lymphatic tissue in the body, located between the stomach and the diaphragm. The parenchyma of the spleen consists of two different kinds of tissue: White pulp and red pulp.
Lymphatic Nodules Egg shaped masses of lymphatic tissue. Scattered throughout the connective tissue of mucous membranes lining the GI tract, Urinary and Reproductive and Respiratory airways.
Non-Specific Resistance: Innate Defenses Present at birth and offer immediate protection against a wide variety of pathogens and foreign substances. External physical and chemical barriers Internal non-specific defenses: antimicrobial proteins, natural killer cells and phagocytes, inflammation and fever.
Non-Specific Resistance First Line of Defense: Skin and mucous membranes: (I) Epidermis (II) Mucous membranes (III) Lacrimal apparatus (lysozyme)
Non-Specific Resistance Second line of Defense: Internal Defenses: (I) Antimicrobial proteins: 3 main types (a) Interferons (b) Complement (c) Transferrins (II) Natural Killer cells and Phagocytes (a) Perforins (bursting) (b) Granzymes (apoptosis) (c) Macrophages (fixed) e.g. Kupffer cells, tissue macrophages in the spleen; Neutrophils.
Phagocytosis Occurs in 5 phases: (I) Chemotaxis: the stimulated movement of phagocytes to a site of damage. (II) Adherence: Attachment of the phagocyte to a microbe or foreign material. (III) Ingestion: Engulfing of the microbe by pseudopods (phagosome). (IV) Digestion: Lysosomes release lysozymes, and additional digestive enzymes, break down microbial cell walls . (V) Killing: The chemical onslaught provided by the lysozyme, digestive enzymes and oxidants quickly kill many types of microbes.
Specific Resistance: Immunity Two properties distinguish specific immunity from non- specific immunity: (a) specificity for particular foreign molecules (allow self to distinguish between non-self). (b) Memory for most previously encountered antigens so that a second encounter prompts an even more rapid and vigorous response.
Specific Resistance: Immunity Maturation of T cells and B cells Types of Immune responses Antigens Complement and Immunity
Maturation of T cells and B cells The cells that develop immunocompetence are lymphocytes called B cells and T cells. Develop in primary lymphatic organs (red bone marrow and thymus). B cells complete their development in red bone marrow. T cells develop from pre-T cells that migrate from red bone marrow into the thymus, where they mature. T- cells exit the thymus as either CD4 or CD8 cells.
T-cells Most T-cells are inactive. T-cell becomes activated only if it binds to a foreign antigen and at the same time is co-stimulated by either a cytokine or plasma membrane molecule.
Types of T-cells Three main types of differentiated T cells: Helper T Cells Cytotoxic T Cells Memory T Cells
B Cells The body contains millions of different B cells, each capable of responding to a specific antigen. During activation of a B cell, an antigen binds to B-cell receptors (BCR’s).
Activation, proliferation and differentiation of B cells into plasma cells and memory cells
Types of Immune Responses Cell mediated immunity: CD8 cells proliferate into cytotoxic T cells that directly attack the antigen. Antibody mediated immune responses: B cells transform into plasma cells, which synthesise and secrete proteins called antibodies.
Antigens Antigens have two important characteristics: (I) Immunogenicity: provoke an immune response (II) Reactivity: ability to react specifically with antibodies or cells it provoked. Epitopes: small parts of a large antigen molecule act as triggers for immune responses. An antibody can combine specifically with the epitope on an antigen that triggered its production.
Major Histocompatibility Complex Antigens Located in the plasma membrane of body cells are self antigens, the major histocompatibility complex (MHC) antigens. Two classes of MHC: Class I and Class II
Antibody Actions All 5 classes of antibodies (IgG, IgA, IgM, IgD and IgE) act to disable antigens. (I) Neutralise antigens (II) Immobilising bacteria (III) Agglutinating and precipitating antigens (IV) Activating complement (V) Enhancing phagocytosis
The role of complement in Immunity The complement system is a defensive system made up of over 30 proteins produced by the liver and found circulating in blood plasma and within tissue throughout the body. Collectively the complement proteins destroy microbes by causing phagocytosis, cytolysis, and inflammation: they also prevent excessive damage to body tissues.
Self- Recognition and Self Tolerance To function properly your T cells must have two traits: (I) Recognise MHC proteins: self-recognition. (II) Lack reactivity: self-tolerance.
Overview of Microbiology Microbiology is the study of microbes. An organism that is visible only with a microscope. Microbes are either autotrophic or heterotrophic. Prokaryotic and Eukaryotic Types of microbes: Viruses, Bacteriophages, Slime moulds, Bacteria, Fungi, Protozoa and Prions.
