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LYMPHATIC SYSTEM

LYMPHATIC SYSTEM. Marieb - Chapter 20. Lymphatic System. capillaries ducts nodes lymphoid organs diffuse cell pockets. Lymphatic capillaries. extremely permeable present throughout body intermingle with blood capillaries not in CNS or mineralized tissues. Lymphatic Ducts. Trunks

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LYMPHATIC SYSTEM

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  1. LYMPHATIC SYSTEM Marieb - Chapter 20

  2. Lymphatic System • capillaries • ducts • nodes • lymphoid organs • diffuse cell pockets

  3. Lymphatic capillaries • extremely permeable • present throughout body intermingle with blood capillaries • not in CNS or mineralized tissues

  4. Lymphatic Ducts • Trunks • Lumbar • Bronchomediastinal • Subclavian • Jugular • Intestinal

  5. Trunks anastomose & enter veinous return at junction of subclavian & jugular veins

  6. Lymph Vessel Structure • much like veins • more valves • more frequent anastomoses

  7. A tropical disease caused by lymphatic obstruction. Victim is bitten by a mosquito infected with a roundworm known as a filarial worm. The resulting edema leads to fibrosis and elephant-like thickening of the skin. ELEPHANTIASIS

  8. Lymphoid organs

  9. Lymph Nodes • Encapsulated by dense fibrous connective tissue • Trabeculae - capsule extends inward form compartments

  10. Lymph Nodes • Clusters at junctions of vessels into trunks

  11. Lymph node structure Figure 20.4a • Cortex • dense follicles with germinal centers • dividing B cells • Deep cortex (T cells) • Medulla • inward extensions of cortical tissue (B, T and plasma cells) • Sinuses • lymph drainage • filtered by macrophages • Circulation in the node: • afferent lymphatic vessel  subcapsular sinus  drain through tissue  hilus  efferent vessels

  12. Lymphoid Organs

  13. Spleen

  14. Spleen

  15. Thymus • primary function is in early life • Secretes thymosin and thymopoietin which causes T lymphocytes to become immunocompetent • Lacks B cells (no follicles) • Atrophies with age: prominent in newborns, stops growth by adolescence, degenerates by old age

  16. Thymus

  17. Lymphoid Follicle Aggregates • MALT (mucosa associated lymphatic tissue) includes: • Peyer’s Patches in intestines • Appendix • Tonsils • Small bronchiolar follicles • MALT are positioned well to: • Destroy bacteria that breach the mucosal membrane from outside • Develop “memory” lymphocytes for long term immunity

  18. Tonsils

  19. Tonsils • not encapsulated • blind pouches – crypts • bacteria can enter • induced immune response

  20. Peyer’s Patches

  21. Peyer’s Patches

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