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BIOL 2402 Exam 2 Review: Lymphatic & Immune Systems

Chapter 21: Lymphatic and Immune Systems

1. Components of the Lymphatic System and Their Function

  • Lymphatic Vessels:

    • Function: Carry lymph (fluid) from tissues back to the bloodstream.
    • Role: Remove excess interstitial fluid, transport fats, and provide immune defense.

  • Lymph:

    • Definition: Fluid that leaks out of capillaries; contains white blood cells, especially lymphocytes.

  • Lymph Nodes:

    • Description: Small bean-shaped organs.
    • Function: Filter lymph and remove pathogens.

  • Primary Lymphoid Organs:

    • Components: Bone marrow and thymus.
    • Purpose: Where lymphocytes are produced and mature.

  • Secondary Lymphoid Organs:

    • Components: Lymph nodes, spleen, tonsils, and MALT.
    • Purpose: Where immune responses are activated.

2. Function of Lymphatic System

  • Return Excess Fluid: Returns excess fluid to the bloodstream.
  • Transport Dietary Fats: Carries dietary fats from the small intestine.
  • Immune Cell Production and Response: Provides sites for immune cells to be produced and activated, defending against pathogens.

3. Consequences of Lymphatic System Failure

  • Lymphedema:
    • Definition: Swelling due to fluid buildup in tissues.
  • Weakened Immune Response:
    • Consequence: Lymphocytes and macrophages cannot properly filter pathogens, leading to increased susceptibility to infections.

4. MALT (Mucosa-Associated Lymphoid Tissue)

  • Definition: Mucosa-Associated Lymphoid Tissue.
  • Location: Found in mucous membranes including tonsils, Peyer’s patches in intestines, and appendix.
  • Function: Protects mucosal surfaces by trapping and destroying pathogens entering through the mouth, nose, or intestines.

5. Importance of Lymph Filtering

  • Purpose of Filtering: Removals of bacteria, viruses, and debris.
  • How Filtering Occurs: Performed by lymph nodes which contain macrophages and lymphocytes.
  • Pathway of Lymph: Lymph travels through lymphatic vessels → lymph nodes → larger ducts → empties into subclavian veins → rejoins bloodstream.

6. Interaction Between Lymphatic and Immune Systems

  • Transport: Lymphatic system transports immune cells (lymphocytes).
  • Trapping Pathogens: Immune system uses trapped pathogens to identify and destroy infections.
  • Functionality: Together, the two systems maintain fluid balance and protect the body from disease.

7. Components of the Immune System

  • Cells:
    • Types: Lymphocytes (B and T cells), macrophages, dendritic cells, natural killer cells.
  • Tissues/Organs:
    • Components: Bone marrow, thymus, spleen, lymph nodes, MALT.
  • Molecules:
    • Components: Antibodies, cytokines, complement proteins.

8. Lines of Defense in Immunity

  1. First Line (Nonspecific):
    • Components: Skin, mucous membranes, secretions (tears, saliva, acid).
  2. Second Line (Innate):
    • Components: Phagocytes, natural killer cells, inflammation, fever, antimicrobial proteins.
  3. Third Line (Adaptive):
    • Components: Specific immune responses by B cells and T cells.

9. Innate vs. Adaptive Immunity

  • Innate Immunity:

    • Present at birth, responds quickly, non-specific (e.g., barriers, phagocytes, inflammation).

  • Adaptive Immunity:

    • Slower to respond but specific to pathogens, involves memory (B and T lymphocytes).

10. Functions of Each Branch of Immunity

  • Humoral (B Cells):
    • Function: Produce antibodies that target specific pathogens in body fluids.
  • Cell-Mediated (T Cells):
    • Function: Attack infected or abnormal cells directly.

11. Types of Leukocytes (WBCs) in Innate Immunity

  • Neutrophils:
    • Role: First responders; they engulf pathogens.
  • Macrophages:
    • Role: Engulf and digest microbes and debris.
  • Dendritic Cells:
    • Role: Present antigens to T cells.
  • Natural Killer (NK) Cells:
    • Role: Destroy virus-infected or cancer cells.

12. Natural Killer (NK) Cells

  • Mechanism of Action: Use perforins and granzymes to destroy infected or tumor cells.
  • Classification: Part of innate immunity (non-specific).

13. Antimicrobial Proteins

  • Interferons:

    • Source: Released by virus-infected cells;
    • Function: Warn neighboring cells and block viral replication.

  • Complement Proteins:

    • Role: Circulate in blood; enhance inflammation, opsonization (marking for phagocytosis), and form the membrane attack complex (MAC) to kill pathogens.

14. Antigen-Presenting Cells (APCs)

  • Types: Dendritic cells, macrophages, B cells.
  • Function: Display fragments of antigens on their surface with MHC (Major Histocompatibility Complex) molecules to activate T cells.

15. Fever

  • Cause: Triggered by pyrogens, which are chemicals released by white blood cells (WBCs).
  • Purpose: Raises body temperature to slow pathogen growth and speed up immune reactions.

16. Inflammation

  • Function: Isolate injury, destroy pathogens, and begin tissue repair.

  • Cardinal Signs: Redness, heat, swelling, pain.

  • Steps Involved:

    1. Release of inflammatory chemicals (histamine, prostaglandins).
    2. Vasodilation and increased permeability.
    3. Phagocyte mobilization.

  • Cytokines:

    • Role: Chemical messengers coordinating immune activity (e.g., interleukins, interferons).
    • Types: Pro-inflammatory, anti-inflammatory, growth factors.

17. Two Branches of Adaptive Immunity

  • Humoral (B Cells): Produce antibodies in response to antigens in body fluids.
  • Cell-Mediated (T Cells): Directly attack infected or abnormal cells.

18. B Cells - Mechanism and Development

  • Development: Made and mature in bone marrow.
  • Activation: Upon activation by an antigen, they form plasma cells (which produce antibodies) and memory B cells.

19. T Cells - Types and Functions

  • Production: Produced in bone marrow, mature in thymus.
  • Types:
    • Helper T (TH): Activate B cells and cytotoxic T cells.
    • Cytotoxic T (TC): Kill infected cells.
    • Regulatory T (TR): Prevent overreaction.
    • Memory T (TM): Remember antigen for faster future responses.

20. Active vs. Passive Immunity

  • Active Immunity: Your body makes its own antibodies through natural infection or vaccination.
  • Passive Immunity: You receive antibodies, such as through mother's milk or injection.

21. Difference Between Antibody and Antigen

  • Antigen: Substance that triggers an immune response.
  • Antibody: Protein produced by B cells that binds to and neutralizes specific antigens.

22. Relationship Between T Cells and APCs; MHC Molecules

  • Role of APCs: Present antigen fragments with MHC molecules.
  • Types of MHC:
    • MHC I: Found on all body cells; recognized by cytotoxic T cells.
    • MHC II: Found on APCs; recognized by helper T cells.

23. Key Figures and Illustrations

  • 21.19: Steps of inflammation.
  • 21.20: Antibody vs. antigen diagram.
  • 21.22: MHC interaction.
  • 21.23–21.26: Immune response pathways and T-cell activation.

Conclusion

  • The lymphatic and immune systems work closely together to protect the body from disease, maintain fluid balance, and respond to infections and injuries efficiently. Understanding the components and functions of each part of these systems is crucial for comprehending overall immune health and responses.