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Lymphatic System and Lymphoid Organs - Anatomy & Physiology

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  • What are the three main parts of the lymphatic system?
    Network of lymphatic vessels, lymph (fluid in vessels), and lymph nodes that cleanse lymph.
  • What is the primary function of the lymphatic system?
    Returns interstitial fluid and leaked plasma proteins back to the blood.
  • What are lymphatic capillaries and where are they absent?
    Blind-ended vessels between tissue cells and blood capillaries; absent from bones, teeth, and bone marrow.
  • How do lymphatic capillaries differ from blood capillaries?
    More permeable; can take up larger molecules like proteins, cell debris, pathogens, and cancer cells.
  • What specialized structures increase permeability of lymphatic capillaries?
    Endothelial cells overlap loosely forming one-way minivalves anchored by collagen filaments.
  • What is the flow direction of lymph in lymphatic vessels?
    One-way system ensuring lymph flows only toward the heart.
  • Name the major lymphatic trunks.
    Paired lumbar, bronchomediastinal, subclavian, jugular trunks, and single intestinal trunk.
  • Where do the right lymphatic duct and thoracic duct drain lymph?
    Right lymphatic duct drains right upper arm and right side of head/thorax; thoracic duct drains rest of body.
  • What mechanisms propel lymph through the lymphatic system?
    Skeletal muscle milking, thoracic pressure changes, valves, arterial pulsations, and smooth muscle contractions.
  • What is lymphedema and what causes it?
    Severe localized edema caused by blocked or removed lymphatic vessels preventing lymph return to blood.
  • What are the two main types of lymphoid cells?
    Immune system cells (T cells and B cells) and supporting cells forming lymphoid tissue structures.
  • What are the primary functions of T cells and B cells?
    T cells manage immune response and destroy infected cells; B cells produce plasma cells that secrete antibodies.
  • What role do macrophages and reticular cells play in lymphoid tissue?
    Macrophages phagocytize foreign substances and activate T cells; reticular cells produce stroma fibers supporting immune cells.
  • What are the two main types of lymphoid tissue?
    Diffuse lymphoid tissue (loose cells and fibers) and lymphoid follicles (solid spherical bodies with proliferating B cells).
  • What are primary and secondary lymphoid organs?
    Primary organs (red bone marrow, thymus) where lymphocytes mature; secondary organs (nodes, spleen) where lymphocytes activate.
  • What are the two main functions of lymph nodes?
    Cleansing lymph by removing microorganisms and debris, and immune system activation by lymphocyte activation.
  • Describe the structure of a lymph node.
    Bean-shaped, less than 2.5 cm, with an external capsule dividing cortex (B and T cells) and medulla (B, T, plasma cells).
  • How does lymph circulate through a lymph node?
    Enters via afferent vessels, flows through subcapsular sinus, cortex and medullary sinuses, exits via efferent vessels at hilum.
  • What is the spleen's role in the lymphatic system?
    Largest lymphoid organ; site of lymphocyte proliferation, blood cleansing, and storage of breakdown products and blood cells.
  • What is MALT and where is it found?
    Mucosa-associated lymphoid tissue found in mucosa of respiratory, genitourinary, and digestive tracts, including tonsils, Peyer's patches, appendix.
  • What is the function of tonsils?
    Gather and remove pathogens in food or air; contain crypts trapping bacteria to activate immune response.
  • What is the thymus and its unique function?
    Bilobed lymphoid organ where T cells mature; contains blood-thymus barrier to prevent premature T cell activation.
  • How does the thymus differ from other lymphoid organs?
    Lacks B cells and does not directly fight antigens; functions strictly in T lymphocyte maturation.
  • What happens to the thymus with age?
    Most active in childhood, stops growing during adolescence, then gradually atrophies but still produces immunocompetent cells.