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Overview of the Lymphatic System Functions ch. 20 whole shabang

Dec 15, 2024

Functions of the Lymphatic System

Key Functions

  • Drainage of Interstitial Fluid

    • Prevents edema by constantly draining interstitial fluid
    • Helps maintain hydrostatic pressure of interstitial fluid near zero mm Hg
  • Filtration and Immunity

    • Lymph nodes & spleen filter debris and pathogens from lymph
    • The spleen recycles old/damaged red blood cells, stores iron (with the liver), and acts as a storage for red and white blood cells
    • White pulp (stores leukocytes) and Red pulp (recycles RBCs)
  • Surveillance and Activation

    • Lymph nodes and lymphoid tissues act as surveillance points for lymphocytes and macrophages
    • Allows housing and proliferation of lymphocytes
    • Absorption of Lipids - Lipids absorbed via lymphatic system before entering circulatory system

Lymphatic Circulation

  • Carries lymph in one direction; lymph is constantly renewed
  • Lymphatic capillaries are more permeable than blood capillaries (loose endothelial overlap creates minivalves)
  • Risks: potential entry of pathogens or cancer cells into lymph

Structures of the Lymphatic System

  • Lacteals: specialized lymphatic capillaries in the small intestine for lipid absorption
  • Lymphatic Vessels: Contain valves to prevent backflow, rely on muscular movement and respiratory pumps to move lymph
  • Lymphatic Ducts: Two largest vessels, return cleansed lymph to circulatory system

Lymphoid Tissues and Organs

  • Primary Lymphoid Organs: Thymus and red bone marrow; sites of lymphocyte maturation
  • Secondary Lymphoid Organs: Lymph nodes, spleen, tonsils, Peyer’s patches, appendix, and MALT; sites of lymphocyte activation

Lymph Nodes

  • Chief secondary lymphoid organs scattered throughout the body
  • Filter lymph, allowing macrophages and lymphocytes to remove debris/pathogens
  • Superficial lymph nodes in neck, armpits, and groin are more noticeable when swollen

Spleen

  • High in the abdomen, near the diaphragm
  • Functions: immune surveillance, storage of blood cells and iron, recycling of RBCs and platelets

Mucosa-associated Lymphoid Tissue (MALT)

  • Found throughout mucous membranes
  • Includes tonsils, Peyer's patches, and appendix

Tonsils

  • Four tonsils: Pharyngeal (single), Palatine (paired), Lingual (single)
  • Offer small surveillance sites for lymphocytes

Thymus

  • Main site for T-cell maturation
  • Atrophies with age

Study Advice

  • Understand primary vs. secondary lymphoid organs
  • Familiarize with locations and functions of lymphatic components
  • Utilize diagrams and tables for memorization and visualization