ch 20

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Author:
swasdo
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276975
Filename:
ch 20
Updated:
2014-06-16 17:07:39
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bio242
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lymphatic system
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  1. what are the three parts of the lymphatic system
    • network of lymphatic vessels
    • lymph: fluid in vessels
    • lymph nodes: cleanse lymph
  2. lymphoid organs and tissues
    • provide structural basis of immune system
    • house phagocytic cells and lymphocytes
    • structure include spleen, thymus, tonsils, other lymphoid tissues
  3. lymphatic vessels
    • return interstitial fluid and leaked plasma proteins back to blood
    • 3 liters a day
    • once interstitial fluid enters lymphatics, it is called lymph.
  4. distribution and structure in the lymphatic vessels
    • it is a one way system; lymph flows toward the heart
    • lymph vessels include: lymphatic capillaries, collecting lymphatic vessels, and lymphatic trunks and ducts
  5. lymphatic capillaries
    • similar to blood capillaries except they are very permeable (take up proteins, cell debris, pathogens, cancer) and pathogens travel throughout body via lymphatics.
    • absent from bones, teeth, bone marrow, CNS
    • lacteals: specialized lymph capillaries present in intestinal mucosa which absorb digested fat and deliver fatty lymph to the blood.
  6. lymphatic collecting vessels
    • similar to veins, except they have thinner walls, more internal valves, and anastomose more frequently.
    • collecting vessels in skin travel with superficial veins
    • deep vessels travel with arteries
    • nutrients supplied from branching vasa vasorum
  7. lymphatic trunks
    formed by union of largest collecting ducts
  8. lymphatic ducts
    lymph delivered into one of two large ducts (right lymphatic duct or thoracic duct)
  9. right lymphatic duct
    drains right upper arm and right side of head and thorax
  10. thoracic duct
    arises as cisterna chyli; drains the rest of the body
  11. lymph transport
    • lymph propelled by:
    • milking action of skeletal muscles
    • pressure changes in thorax during breathing
    • valves to prevent backflow
    • pulsations of nearby arteries
    • contractions of smooth muscle in walls of lymphatics
  12. lymphocytes
    • main warriors of immune system.
    • arise in red bone marrow
    • marrow into either T cells or B cells
  13. T and B cells protect against
    antigens
  14. antigen
    • anything the body perceives as foreign.
    • e.g. bacteria, bacterial toxins, viruses, cancer cells, mismatched RBCs
  15. T cells
    • manage immune response
    • attack and destroy infected cells
  16. B cells
    • produce plasma cells, which secrete antibodies
    • antibodies mark antigens for destruction by phagocytosis or other means
  17. macrophages
    phagocytize foreign substances; help activate T cells
  18. dendritic cells
    capture antigens and deliver them to lymph nodes
  19. reticular cells
    produce reticular fiber stroma that supports other cells in lymphoid organs
  20. lymphoid tissue
    • houses ¬†and provides proliferation site for lymphocytes
    • surveillance vantage point for lymphocytes and macrophages
    • largely reticular connective tissue
    • two main types: diffuse lymphoid tissue and lymphoid follicles
  21. what are the two main types of lymphoid tissue
    • diffuse lymphoid tissue: every body organ; larger collections in lamina propria of mucous membranes
    • lymphoid follicles: solid, spherical bodies of tightly packed lymphoid cells and reticular fibers. germinal centers of proliferating B cells, may form part of larger lymphoid organs, isolated aggregations of peyers patches in appendix
  22. where are Peyer's patches found
    appendix
  23. lymph nodes
    • principal lymphoid organs of body
    • embedded in connective tissue, in clusters along lymphatic vessels
    • near body surface in inguinal, axillary, and cervical regions of body
  24. what are the functions of lymph nodes
    • filter lymph: macrophages destroy microorganisms and debris
    • immune system activation: lymphocytes activated and mount attack against antigens
  25. structure of a lymph node
    • vary in shape and size but most are bean shaped
    • external fibrous capsule
    • trabeculae extend inward and divide node into compartments
    • two histologically distinct regions: cortex, medulla
  26. what are the two histologically distinct regions of a lymph node
    cortex and medulla
  27. cortex of a lymph node
    • contains follicles with germinal centers, heavy with dividing B cells
    • dendritic cells nearly encapsulate follicles
    • deep cortex houses T cells in transit
    • T cells circulate continuously among blood, lymph nodes, and lymph
  28. lymph sinuses contain
    macrophages
  29. are there more efferent or afferent vessels into the lymph nodes
    more afferent; this is so the flow is somewhat stagnate and allows lymphocytes and macrophages time to function and do their jobs
  30. spleen
    • largest lymphoid organ
    • serbed by splenic artery and vein, which enter and exit at the hilum
    • functions: site of lymphocyte proliferation and immune surveillance and response; cleanses blood of aged cells and platelets, macrophages remove debris
    • stores and breakdown products of RBCs for later use
    • stores blood platelets and monocytes
    • encased by fibrous capsule
    • has trabeculae
    • contains lymphocytes, macrophages, and huge numbers of erythrocytes
  31. what are the two distinct areas of the spleen
    white pulp and red pulp
  32. white pulp of the spleen
    • around central arteries
    • mostly lymphocytes on reticular fibers; involved in immune functions
  33. red pulp of spleen
    • in venous sinuses and splenic cords
    • rich in RBCs and macrophages for disposal of worn-out RBCs and bloodborne pathogens
    • composed of splenic cords and sinusoids
  34. thymus
    • important functions early in life
    • found in inferior neck; extends into mediastinum; partially overlies heart
    • increases in size and most active during childhood
    • stops growing during adolescence, then gradually atrophies
    • thymic lobules contain outercortex and inner medulla
    • most thymic cells are lymphocytes
  35. describe the size of the thymus throughout life
    small and active as a child, continually grows until it stops during adolescence and gets smaller as you are an adult
  36. how does the thymus differ from other lymphoid organs
    • has no follicles because it lacks B cells
    • does not directly fight antigens. it functions strictly in T lymphocyte maturation.
    • the stroma of epithelial cells (not reticular fibers) provide environment in which T lymphocytes become immunocompetent
  37. MALT
    mucosa associated lymphoid tissue
  38. what is MALT (characteristics)
    • lymphoid tissues in mucous membranes throughout body
    • protects from pathogens trying to enter body
    • largest collections of MALT in tonsils, peyer's patches, appendix
    • also in mucosa of respiratory and genitourinary organs; rest of digestive tract
  39. tonsils
    • simplest lymphoid organs
    • form ring of lymphatic tissue around pharynx
    • gather and remove pathogens in food or air
    • contain follicles with germinal centers
    • not fully encapsulated
    • overlying epithelium invaginates forming tonsillar crypts
  40. list and describe the location of the different types of tonsils
    • palatine: posterior end of oral cavity
    • lingual tonsil: grouped at base of tongue
    • pharyngeal tonsil: posterior wall of nasopharynx
    • tubal tonsils: surrounding openings of auditory tubes into pharynx
  41. what does tonsillar crypts do
    • trap and destroy bacteria and particulate matter
    • allow immune cells to build memory for pathogens
  42. peyer's patches
    • clusters of lymphoid follicles
    • in wall of distal portion of small intestine
    • similar structures are also found in appendix
  43. peyer's patches and appendix
    • destroy bacteria preventing them from breaching intestinal wall
    • generate memory lymphocytes

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