UNIT 2 (lymphatic, immune)

• the lymphatic system is part of the immune system
• there are 500 - 600 lymph nodes throughout the body
• the lymphatic system maintains fluid balance
• the lymphatic system defends body against infection
• the lymphatic system drains interstitial fluid
• the lymphatic system transports dietary lipids
• lymph

  • from interstitial fluid
  • around 4 liters absorbed everyday
  • contains wbcs, chyle, bacteria, cellular debris, plasma proteins
• lymph vessels start as lymphatic capillaries in interstitial spaces
• lymphatic capillaries have flap minivalves

  • open and reabsorb when interstitial pressure increases
  • close when lymph capillary pressure increases
• capillaries

  A) blood

  B) lymphatic

  
• lymph capillary valves close when pressure increases where?

  inside the lymph capillary
• lymph organs include

  • lymph nodes
  • thymus
  • spleen
  • appendix
  • tonsils
• lymph fluid is moved proximally

  • skeletal muscle contraction
  • intrathoracic pressure in inhalation
• skeletal muscles squeeze lymph vessels, pushing lymph proximally
• inspiration decreases thoracic pressure and increases abdominal pressure, moving lymph superiorly
• lymph circulation pathway

  1. capillaries
  2. vessels
  3. nodes
  4. trunks
  5. ducts
  6. subclavian veins
  7. right atrium
• two main lymphatic ducts

  • right lymphatic duct
  • thoracic duct
• right lymphatic duct

  • drains lymph from upper right quadrant (r. head, thorax, arm)
  • empties in to right subclavian vein
• thoracic duct

  • the larger duct
  • drains from most of the body
  • empties to left subclavian vein
• lymphatic

  A) cervical lymph nodes

  B) right lymphatic duct

  C) right subclavian vein

  D) axillary lymph nodes

  E) thymus gland

  F) thoracic duct

  G) spleen

  H) tonsil

  I) left subclavian vein

  J) inguinal lymph nodes

  
• lymphedema

  • the swelling due to accumulation of lymph fluid
  • can occur when lymph nodes/vessels are removed/damaged
• lacteals

  • capillaries that collect lymph from small intestinal villi
• chyle

  • lymph in small intestinal villi
  • milky white due to dietary digested fat
  • collects in cisterna chyli before draining in thoracic duct
• chyle is collected in the cisterna chyli before draining in the thoracic duct
• id

  A) tonsils

  B) cervical lymph nodes

  C) right lymphatic duct

  D) thymus

  E) thoracic duct

  F) cisterna chyli

  G) axillary lymph nodes

  H) thoracic duct

  I) spleen

  J) mucosa associated lymphoid tissue

  K) inguinal lymph nodes

  
• reticular connective tissue is made of interlacing reticular fibers
• reticular connective tissue provides structural support for lymphoid organs
• primary lymphoid organs

  • immature lymphocytes develop
  • stem cells differentiate and mature to immune competent cells
• primary lymphoid organs

  • thymus
  • bone marrow
• secondary lymphoid organs

  • immune surveillance
  • rapid immune response
  • maintenance of protective immunity
• secondary lymphoid organs

  • spleen
  • lymph nodes
  • lymphatic nodes / follicles
  • tonsils
  • appendix
  • payer's patches
• lymphatic nodules / follicles

  • not surrounded by connective tissue capsule
  • clusters of lymphocytes / macrophages
  • dense masses
• lymphatic nodules / follicles include...

  • tonsils
  • appendix
  • peyer's patches
• lymph nodes

  • filter and purify lymph before it reaches venous system
  • small kidney shaped organs
• lymph enters nodes through afferent vessels and leaves through efferent vessels
• movement of lymph through node

  1. afferent vessel
  2. sinus
  3. outer cortex
  4. deep cortex
  5. medulla
  6. efferent vessel
• trabeculae divide the node in to nodules
• germinal centers hold actively dividing B lymphocytes
• lymph node groups

  • inguinal
  • axillary
  • cervical
  • mediastinal
  • popliteal
• why lymph nodes swell

  • reaction to infection (both direct and just in general)
  • contact with foreign material from infected tissue