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Lymphatic System and Immunity - Anatomy & Physiology

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  • Main components of the lymphatic system
    Lymphatic vessels transport lymph, and lymphatic tissues/organs (tonsils, lymph nodes, spleen, thymus) house immune cells and filter pathogens.
  • Primary functions of the lymphatic system
    Regulates interstitial fluid volume, absorbs dietary fats, and supports immune functions by filtering pathogens and housing leukocytes.
  • How does lymph flow through the body?
    Lymph flows in low-pressure vessels with valves preventing backflow, moved by muscle contractions and smooth muscle in vessel walls.
  • What causes lymphedema?
    Severe swelling from excess interstitial fluid due to lymphatic vessel removal or blockage, such as after surgery or parasitic infection.
  • Structure and function of lymphatic capillaries
    Blind-ended vessels with endothelial flaps allowing fluid, macrophages, bacteria, and cancer cells to enter lymph from tissues.
  • What is MALT and where is it found?
    Mucosa-Associated Lymphatic Tissue protects mucous membranes in GI, respiratory, and genitourinary tracts; includes tonsils, Peyer's patches, and appendix.
  • Role of lymph nodes
    Small bean-shaped clusters that filter lymph, contain B and T cells, macrophages, and dendritic cells; lymph enters via afferent and exits via efferent vessels.
  • Functions of the spleen's red and white pulp
    Red pulp destroys old erythrocytes; white pulp contains leukocytes that filter pathogens from blood.
  • Role of the thymus in immunity
    Site of T cell maturation and screening; secretes hormones to generate functional T cells; atrophies with age.
  • Three lines of immune defense
    First line: surface barriers; second line: innate immunity; third line: adaptive immunity.
  • Characteristics of innate immunity
    Nonspecific, rapid response to all pathogens; includes cells like macrophages, neutrophils, NK cells, and proteins like complement.
  • Key cells in innate immunity
    Macrophages, neutrophils, eosinophils, dendritic cells, natural killer cells, basophils, and mast cells.
  • Complement system activation pathways
    Classical (antibody-bound), lectin (microbial carbohydrates), and alternative (C3 cleavage) pathways activate complement proteins.
  • Functions of activated complement proteins
    Cause cell lysis, enhance inflammation, neutralize viruses, opsonize pathogens, and clear immune complexes.
  • Role of cytokines in immunity
    Regulate immune cell activity; examples include TNF (attracts phagocytes), interferons (inhibit viruses), and interleukins (stimulate leukocytes).
  • Phases of the inflammatory response
    Release of mediators causing redness, heat, swelling, pain; followed by phagocyte response ingesting pathogens and debris.
  • How does fever aid immunity?
    Elevated body temperature enhances phagocyte efficiency and recovery; pyrogens trigger hypothalamus to raise temperature.
  • Difference between cell-mediated and antibody-mediated immunity
    Cell-mediated uses T cells to target infected or cancerous cells; antibody-mediated uses B cells and antibodies to neutralize pathogens.
  • Major Histocompatibility Complex (MHC) classes and functions
    Class I MHC on all nucleated cells presents endogenous antigens to cytotoxic T cells; Class II MHC on APCs presents exogenous antigens to helper T cells.
  • Process of T cell activation
    Dendritic cells present antigen on MHC to T cells, triggering clonal selection and differentiation into effector and memory T cells.
  • Functions of helper and cytotoxic T cells
    Helper T cells secrete cytokines activating immune cells; cytotoxic T cells kill infected or abnormal cells via perforin and apoptosis enzymes.
  • Steps in B cell activation and antibody production
    B cell binds antigen, presents it on MHC II, receives helper T cell cytokines, then divides into plasma cells (antibody producers) and memory B cells.
  • Classes of antibodies and their roles
    IgG (most common, crosses placenta), IgA (secretions), IgM (first produced), IgE (allergies, parasites), IgD (B cell receptor).
  • Antibody functions
    Agglutination, opsonization, neutralization, complement activation, and stimulation of inflammation.
  • Primary vs secondary immune response
    Primary: slower, IgM dominant, antibody peak in 7–14 days; Secondary: faster, IgG dominant, peak in 3–5 days with memory cells.
  • Types of immunity: active vs passive
    Active immunity results from infection or vaccination with long-lasting memory; passive immunity is transfer of antibodies, short-term protection.
  • Types of hypersensitivity disorders
    Type I: immediate allergies; Type II: antibody-mediated; Type III: immune complex-mediated; Type IV: delayed T cell-mediated.
  • Causes of immunodeficiency disorders
    Primary: genetic or developmental defects; Secondary: acquired from infections (e.g., HIV), cancer, or medications.
  • Mechanisms of autoimmune disorders
    Failure of self-tolerance due to sequestered antigen release, molecular mimicry, abnormal MHC expression, or nonspecific B cell activation.