Pre-Medicine

/

MCAT

/

Lymphatic

Previous
Next

Lymphatic System

76
Watch Video

Lymphatic System 

  • Lymph is a liquid formed by
    • interstitial fluid leaked from capillaries
      • Any fluid not reabsorbed by capillaries will be drained into lymphatic vessels
      • Transport of proteins and large particles (e.g. waste products) that are too large to directly enter the capillaries
    • Fats from intestines
      • Absorbed lipids from food packaged into large droplets, called chylomicrons
      • Droplets are too large to directly cross over into blood; transported through the lymphatic system to indirectly enter circulation
  • Structure
    • Lymphatic vessels
      • Function: collection and transport of lymph
        • Contain one-way valves to ensure unidirectional movement
        • Overlapping endothelial cells form walls of lymphatic vessels to prevent leakage
        • Smooth muscle around vessels contracts to push fluid along
        • Adjacent skeletal muscle can also pushes fluid forward
          • Lymph flow is greater in an active person than an individual at rest
      • Lacteals are lymphatic vessels in the small intestine
        • Function: absorb fat as chylomicrons 
      • Order of flow
        • Lymph capillaries lymph vessels lymph duct → veins
          • Dumped into veins via lymphatic ducts, which include the thoracic duct and right lymphatic duct
    • Lymph nodes
      • Small clusters of cells along lymphatic vessels
      • Function: filters lymph as it flows through
        • Monitoring by resident lymphocytes
          • Scan for foreign antigens in lymph, launching immune responses if necessary
          • Macrophages also destroy pathogens via phagocytosis
    • Spleen
      • Largest organ in the lymphatic system
      • Function: filters blood
        • WBCs in spleen recognize and bind foreign antigens in blood
          • Can launch immune responses if necessary
        • Splenic macrophages destroys old and damaged RBCs
        • Stores extra blood components (e.g. platelets, RBCs)