Lymphatic System and Immune Response thru Compliment Protein activation Notes

Lymphatic System Overview

  • Lymphatic System Role: The lymphatic system is crucial for returning excess interstitial fluid to the cardiovascular system to prevent edema (swelling).

  • Lymphatic Capillaries:

    • Structure: Close-ended, associated with cardiovascular capillary beds.
    • Function: Absorb excess interstitial fluid and substances (e.g., pathogens, cancer cells).
    • Lymph Fluid Composition: Similar to blood plasma but lacks red blood cells and most proteins.

Lymphatic Fluid Flow

  • Pathway:
    1. Lymph fluid enters lymphatic capillaries from tissue space.
    2. Transports to collecting vessels, which contain one-way valves to prevent backflow (due to low pressure).
    3. Moves through lymph nodes for filtration (removes toxins, pathogens, cellular debris).

Lymphatic Vessels and Ducts

  • Collecting Vessels: Return lymph fluid to larger trunks and lymphatic ducts.
  • Lymphatic Ducts:
    • Right Lymphatic Duct: Drains lymph from right upper body into right subclavian vein; smaller in size.
    • Thoracic Duct: Larger, drains lymph from left upper body, abdominal cavity, and lower limbs into the left subclavian vein.

Importance of Lymph Nodes

  • Filtering Action: Lymph nodes filter lymph fluid, ensuring removal of pathogens and debris before fluids re-enter the bloodstream.
  • Cancer Implications: Presence of cancer cells in lymph nodes may indicate the need for surgical removal of nodes in some cancers (e.g., breast cancer).

Lymphatic Cells

  • Cell Types: Includes natural killer cells, T cells, B cells, dendritic cells, macrophages, monocytes.
  • Natural Killer Cells: Target and destroy infected or cancerous cells.
  • T Cells and B Cells: Involved in adaptive immunity; form memory cells for quicker response on re-exposure to pathogens.
  • Macrophages and Dendritic Cells: Act as antigen-presenting cells, crucial for activating T cells and B cells.

Organs Involved in the Lymphatic System

  • Red Bone Marrow: Site for blood cell production; source of lymphocytes (T cells and B cells).
  • Thymus: Maturation site for T cells; critical for immune system development, especially in infancy.
  • Spleen: Filters blood; contains white and red pulp for immune response and red blood cell removal.

Immune Response Mechanisms

  • Innate Immunity: First line of defense; includes immediate responses through barriers (skin, mucosa) and innate immune cells (neutrophils, eosinophils, basophils).
  • Adaptive Immunity: Takes longer; involves specific responses to pathogens through memory T cells and B cells that produce antibodies.

Antimicrobial Proteins and Pathways

  • Interferons: Proteins released by infected cells to inhibit virus spread and activate immune cells.
  • Complement System: Series of proteins that help destroy pathogens through different pathways (classical, alternative, lectin). Each pathway activates components leading to inflammation and clearance of pathogens.

Summary of Specific Immune Cells

  • Neutrophils: Most abundant; primary responders to bacterial infection; engage in phagocytosis and produce reactive oxygen species.
  • Eosinophils: Deal with parasites; involved in allergic reactions.
  • Basophils: Least common; aid in inflammation response through histamine release; attract other immune cells.
  • Monocytes: Differentiate into macrophages and dendritic cells after entering tissues; involved in the phagocytosis of pathogens.

Conclusion

  • The lymphatic system plays an essential role in fluid balance, immune response, and the filtration of pathogens. Understanding its structure and function is crucial for recognizing and combating diseases.