Lympathic system

• Body systems


  Major systems that work together to enable organisms to function
• There are 11 major body systems
• Body systems don't work in isolation, they are interconnected
• Musculoskeletal system


  Combination of muscular and skeletal systems
• Urinary system


  Part of the excretory system
• Lymphatic system


  Often lumped with the immune system, but deserves its own focus
• Interstitial fluid


  Fluid found outside of cells, between cells, surrounding cells
• Lymph


  Fluid that doesn't get reabsorbed by blood capillaries and enters the lymphatic system
• Lymph


  • Derived from blood plasma
  • Can contain proteins, lipids, and lipid-soluble vitamins
• Lymph movement


  1. Enters lymphatic capillaries

  2. Travels through lymphatic vessels

  3. Drains into lymphatic ducts

  4. Returned to circulatory system
• Lymphatic ducts


  • Right lymphatic duct (upper right body)
  • Thoracic duct (rest of body)
• The thoracic duct handles a larger lymph workflow than the right lymphatic duct
• Lymph nodes


  • Filter lymph, removing cellular debris and pathogens
  • Contain immune cells like lymphocytes and macrophages
• Spleen


  Lymphatic organ that filters blood and has areas for immune response
• Tonsils


  • Palatine tonsils
  • Pharyngeal tonsils (adenoids)
  • Lingual tonsils
  • Tubal tonsils
• Primary lymphoid organs


  • Bone marrow (B cell development)
  • Thymus (T cell maturation)
• Secondary lymphoid organs/tissues


  Lymph nodes, spleen, tonsils (where lymphocytes take action, but don't develop)
• The thymus is most active before puberty, then decreases in activity as a person ages
• Lymphedema


  Swelling caused by compromised lymphatic system function and accumulation of lymph in tissues
• Lymphatic filariasis is a disease where a parasitic nematode worm can damage the lymphatic system and cause lymphedema
• The nematode worms that cause lymphatic filariasis are transmitted by mosquitoes
• Lymph

  Clear water (in Latin), the fluid that flows through the lymphatic vessels and lymph nodes which make up the lymphatic system
• Lymphatic system


  • Returns fluid from the tissues back to the heart
  • Helps large molecules like hormones and lipids enter the blood
  • Helps with immune surveillance to keep infections from running amok
• Fluid movement from blood to interstitial space

  1. Blood in arteries under pressure

  2. Fluid and small proteins seep out of capillaries

  3. 17 liters reabsorbed, 3 liters left behind in tissues
• Lymphatic vessels/lymphatics


  Collect excess interstitial fluid and return it to the blood
• Lymphatic capillaries


  • Extremely permeable walls made of endothelial cells that only loosely overlap
  • Endothelial cells anchored to interstitial structures by collagen filaments
  • Open when interstitial pressure is greater, close when interstitial pressure is less
• Lymphatic trunks

  • Two lumbar trunks
  • Two bronchomediastinal trunks
  • Two subclavian trunks
  • Two jugular trunks
  • One intestinal trunk
• Right lymphatic duct


  Collects lymph from right arm and right side of head and chest
• Thoracic duct


  Collects lymph from rest of body
• Lymphatic system advantages


  • Can pick up larger molecules like hormones that are too large for capillaries
  • Can help get nutrients to tissues (e.g. transport chylomicrons)
• Lymphoid organs

  • Remove foreign material from lymph to keep it from entering bloodstream
  • Act as lookout points for immune defenses
• Types of lymphoid organs

  • Diffuse lymphoid tissue (e.g. lining of GI and respiratory tract)
  • Lymph nodes
  • Spleen
  • Thymus
  • Tonsils
• Lymph node function

  1. Unfiltered lymph drains into lymph node

  2. Dendritic cells detect pathogens and present antigens to B cells

  3. B cells turn into plasma cells and produce antibodies
• Spleen


  • White pulp filters out antibody-coated bacteria and generates antibodies
  • Red pulp destroys old/defective blood cells and recycles components
• Thymus


  Involved in development of T cells, destroys T cells that react to self-antigens
• Tonsils trap pathogens from food and air