Lymphatic System

• Purpose:

  • Collect fluid still in tissues and return it to the circulatory system
  • Blood enters capillaries at high pressure
  • Forces some fluid into tissue through capillary wall
  • Some but not all fluid returns to capillary at vein
  • Internal defense against disease causing organisms
• • Lymph: a clear liquid that contains a high number of lymphocytes (a type of white blood cells) and plasma
• Structure:

  • One way – carries fluid away from tissues ( doesn’t circulate like blood) due to blind ended capillaries
  • These capillaries are highly permeable
  • Network lymph capillaries joined to larger lymph vessels
• • Lymph nodes: which filter the lymph as it passes through them and add lymphocytes to it.
• Lymphatic System


  Blood enters at high pressure, fluid leaks
• Lymphatic System


  • Blind open-ended tubes collects lymph (fluid)
  • Lymph vessels have valves (prevent backflow)
  • Lymph vessels have smooth muscle layer & skeletal muscle layer that contract to move lymph along vessels
• Lymph Node/Gland


  • Occur at intervals along lymphatic vessels
  • Contain connective tissue framework
  • Within are masses of lymphoid tissue containing lymphocytes, macrophages and plasma cells
  • Spaces between cells of lymphoid tissue criss-crossed by network of fibres
  • Lymph enters node, filters through spaces
  • Large particles like bacteria get trapped in fibres
  • Macrophages destroy pathogens via phagocytosis
  • Swell in node during infections due to increase production of lymphocytes
• Lymph enters circulatory system

  Via veins in chest (lymphatic ducts)
• The Lymphatic system:

  • The lymphatic system and lymph is a secondary transport system that protects and maintains the body by producing and filtering lymph
  • Lymph is filtered at points called lymph nodes where pathogens are removed before fluid is returned to venous circulation
• Lymph vessels:

  • The major vessels are:
  • The thoracis duct - it begins near the lower part of the spine and collects lymph from the pelvis, abdomen and lower chest
  • The right lymphatic duct - it collects lymph from the right side of the neck, chest and arm and empties into a large vein near the right side.
• Other Lymphatic functions:

  • In addition to its key immune function, the lymphatic system also absorbs fats from the gut and extra fluids from all over the body
  • In this respect the lymphatic system plays an important role in lipid transport and maintaining a viable blood pressure