The Lymphatic System & Lymphoid Organs And Tissues


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The Lymphatic System & Lymphoid Organs And Tissues

  1. 1. The Lymphatic System & Lymphoid Organs and Tissues Assoc.Prof. Dr. Karim Al-Jashamy MSU/IMS 2010
  2. 2. Introduction – Components • Lymph is the fluid • Vessels – lymphatics • Structures & organs – Functions • Return tissue fluid to the bloodstream • Transport fats from the digestive tract to the bloodstream • Surveillance & defense
  3. 3. Lymphatics – Originate as lymph capillaries – Capillaries unite to form larger vessels • Resemble veins in structure • Connect to lymph nodes at various intervals – Lymphatics ultimately deliver lymph into 2 main channels • Right lymphatic duct – Drains right side of head & neck, right arm, right thorax – Empties into the right subclavian vein • Thoracic duct – Drains the rest of the body – Empties into the left subclavian vein
  4. 4. Main Channels of Lymphatics
  5. 5. Lymphatic System: Overview • Consists of two semi-independent parts: • A network of lymphatic vessels • Lymphoid tissues and organs scattered throughout the body • Returns interstitial fluid and leaked plasma proteins back to the blood • Lymph – interstitial fluid once it has entered • lymphatic vessels
  6. 6. Lymphatic System: Overview
  7. 7. Lymphatic Vessels • One-way system, lymph flows toward the heart • Lymph vessels include:  Microscopic, permeable, blind-ended capillaries  Lymphatic collecting vessels Trunks and ducts
  8. 8. Lymphatic Capillaries Similar to blood capillaries, with modifications: Very permeable Loosely joined endothelial minivalves Withstand interstitial pressure and remain open The minivalves function as one- way gates that:  Allow interstitial fluid to enter lymph capillaries Do not allow lymph to escape from the capillaries
  9. 9. Lymphatic Capillaries During inflammation, lymph capillaries can absorb: Cell debris Pathogens Cancer cells Cells in the lymph nodes cleanse and “examine” this debris  Lacteals – specialized lymph capillaries present in intestinal mucosa.  Absorb digested fat and deliver chyle to blood of the partial blood vessels
  10. 10. Lymphatic Collecting Vessels Have the same three tunics as veins Have thinner walls, with more internal valves Anastomose more frequently Collecting vessels in the skin travel with superficial veins Deep vessels travel with arteries Nutrients are supplied from branching vasa vasorum
  11. 11. Lymphatic Trunks Lymphatic trunks are formed by the union of the largest collecting ducts Major trunks include: Paired lumbar, bronchomediastinal, subclavian, and jugular trunks A single intestinal trunk
  12. 12. Lymph is delivered into one of two large trunks Right lymphatic duct – drains the right upper arm and the right side of the head and thorax Thoracic duct – arises from the cisterna chyli and drains the rest of the body
  13. 13. Lymphatic Trunks
  14. 14. Lymph Transport The lymphatic system lacks a pumping organ Vessels are low-pressure conduits Uses the same methods as veins to propel lymph: Pulsations of nearby arteries.  Contractions of smooth muscle in the walls of the lymphatics
  15. 15. Lymphoid Cells Lymphocytes are the main cells involved in the immune response Two main varieties: T cells B cells
  16. 16. Lymphocytes T cells and B cells protect the body against Antigens Antigen – anything the body perceives as foreign Bacteria and their toxins; viruses Mismatched RBCs or cancer cells
  17. 17. Lymphocytes T cells Manage the immune response Attack and destroy foreign cells B cells Produce plasma cells, which secrete antibodies Antibodies immobilize antigens
  18. 18. Other Lymphoid Cells Macrophages – phagocytes foreign substances and help activate T cell
  19. 19. Dendritic cells – spiny-looking cells with functions similar to macrophages
  20. 20. Reticular cells – fibroblast–like cells that produce a stroma, or network, that supports other cell types in lymphoid organs