Histo Lecture 7

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Histo Lecture 7
2010-09-26 14:12:23

CT Proper
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  1. 2 Cell types of CT proper
    • -Fibrocyte
    • -Fibroblast
  2. 3 Fiber types of CT proper
    • -Collagen
    • -Elastic
    • -Reticular fibers
  3. 2 types of matrix of CT proper
    • -Ground substance (PGs, GAGs)
    • -Tissue fluid
  4. Functions of Fibrocytes
    • -Quiescent cell, low activity for maintaining fibers and ground substance of ECM
    • -Stimulated to become active (fibroblast) upon injury or tissue damage (for wound healing)
  5. Functions of Fibroblasts
    • -Intesnse synthetic activity for collagen and ground substance molecules
    • -Cytoplasm contains large amounts of ER and developed golgi apparatus
  6. 4 types of Molecules found in ECM
    • -Collagen
    • -Elastin
    • -Proteoglycans
    • -Glycoproteins
  7. Describe collagen
    • -Main fiber of ECM; resists tensile force to provide strength to tissue
    • -Most abundant protein in human body - 30% of dry weight
    • -25 different types of collagen - classified into groups
  8. Describe Elastin
    Provides resiliency (allows stretching) to tissue
  9. Describe proteoglycans
    Filamentous protein core with attached GAGs; provide framework for ECM
  10. Describe glycoproteins
    Proteins bound to small carbohydrate molecules; provide framework for ECM
  11. Synthesis, Location, and Main function of:
    Type I Collagen
    • -Synthesis: Fibroblast or Osteoblast
    • -Location: Bone tendon, ligaments
    • -Main Function: Resist tension
  12. Synthesis, Location, and Main function of:
    Type II Collagen
    • -Synthesis: Chondroblast
    • -Location: Cartilage
    • -Main Function: Resist compressive forces, shear forces at surface
  13. Synthesis, Location, and Main function of:
    Type III collagen
    • -Synthesis: Fibroblast
    • -Location: Pliable tissues (Blood vessels, uterus, GI tract, skin, muscle)
    • -Main Function: Structural maintenance in expandable organs; inital collagen of wound repair
  14. Synthesis, Location, and Main function of:
    Type IV collagen
    • -Synthesis: Fibroblast
    • -Location: Basement membranes (muscle cells, epithelial cells, adipocytes)
    • -Main function: Support of delicate structures; Filtration
  15. Describe Tropocollagen
    • -The protein unit that polymerized to form collagen fibrils
    • -3 subunit polypeptide chains intertwined in a triple helix
    • -Differenes in the chemical structure of these polypeptide chains are responsible for the variuos types of collagen
  16. Describe collagen fibrils
    • -Thin, elongated structures
    • -Several micrometers long
  17. Describe collagen fibers
    -Fibrils aggregate to form fibers (Types I and III)
  18. Describe collagen bundles
    • -Collection of collagen fibers (Type I)
    • -Type II - no fibers/bundles
    • -Type III - no fibrils or fibers
  19. Describe the defect and symptom of Ehlers-Danlos Type VII
    • -Defect: Decrease in procollgaen peptidase activity
    • -Symptoms: Increased articular mobility; Frequent subluxation
  20. Describe the defect and symptom of Scurvy
    • -Defect: Lack of Vitamin C (no procollagen formation)
    • - Symptoms: Ulceration of gums; Hemorrhages; Weak bones
  21. Describe the defect and symptom of Osteogensis imperfecta
    • -Defect: Change of one nucleotide in genes for collagen Type I
    • -Symptoms: Spontaneous fratures; Cardiac insufficiency
  22. Describe the defect and symptom of Keloid scarring
    • -Defect: Hyper-production of collagen
    • -Symptoms: Local swelling that forms in scars of the skin
  23. Describe Reticular Fibers
    • -Composed of Type III collagen fibers
    • -Very thin, small and loosely packed fibers
    • -Fibers bound together and to ECM with abundant interfibrillar bridges with proteoglycans and glycoproteins
    • -Reticular fibers provide framework for organs (lymph nodes, spleen, bone marrow, liver)
  24. Describe Elastic Fibers
    • -Rich in the protein elastin
    • -Rubber-like qualities
    • -5X more extensible than rubber
    • -Desmosine and isodesmosine provide covalent bonds that form cross-links between elastin fibers
  25. Give the Synthesis, Location, and Main function of:
    Elastic Fibers
    • -Synthesis: Fibroblast; Smooth muscle cells
    • -Location: Pliable tissue (blood vessels, uterus, etc.)
    • -Main function: Elongation without deformation
  26. What happens to Elastic fibers wth aging?
    Fibers are replaced by Type I collagen; tissues lose elasticity (more easily deformed)
  27. Describe Marfan syndrome
    • -Genetic mutation; disrupts proper elastin fiber synthesis
    • -Tissues rich in elastic fibers most affected (large/medium-sized arteries contain large amounts of elastin)
    • -Creates non-compliant (brittle) tissue, especially arteries, that are prone to rupture
  28. Describe Ground Substance
    • -Highly hydrated and viscous complex of macromolecules
    • -Composed mainly of PGs, GAGs, glycoproteins and small amount of tissue fluid
  29. Function of Ground Substance
    • -Fills spaces between cells and fibers of CT and provides a pathway for waste and nutrient exchange
    • -Fluid provides for lubrication of ECM
    • -Provides a barrier to penetration of foreign (infectious) agents
  30. Properties of Tissue Fluid
    • -Small quantity within ECM
    • -Similar to blood plasma in content (plasma proteins, ions, diffusible substances)
    • -GAGs bind to water of ECM to maintain hydration of tissue (makes overall tissue more inelastic)
  31. Name the location, components, functions, and cell that contain:
    Loose (Areolar) CT
    • -Cells: Macrophage, mast cell, endothelial cell, neuron
    • -Location: surrounds muscles, nerves, adipocytes, blood and lymphatic vessels
    • -Components: Loosely packed collagen fibers. More elastic and reticular fibers. Well vascularized. Innervated
    • -Functions: Supports epithelial cells of organs and skin. slight resistance to stress in alld irections. Provides blood supply to tissues it surrounds
  32. Name the location, components, functions, and cell that contain:
    Dense Irregular CT
    • -Cells: Macrophage, mast cell
    • -Location: Skin, fascia, joint capsule, periosteum, pericardium, leura
    • -Components: Densely packed collagen fibers. Few elastic or reticular fiber. Not well vascularized. Innervated
    • -Functions: Moderate resistance to stress in all directions
  33. Name the location, components, functions, and cell that contain:
    Dense Regular CT
    • -Cells: Macrophage, mast cell
    • -Location: Tendon, Ligament
    • -Components: Densely packed collagen fibers; Fibers oriented in parallel; Few elastic/reticular fibers; not well vascularized; innervated
    • -Functions: Strong mechanical resistance to stress in a single direction
  34. Describe a Tendon
    • -Collection of collagen fiber bundles
    • -Collagen bundles are enveloped by loose CT containing blood vessels and nerves
    • -Externally, many tendons are surrounded by a sheath of dense CT
  35. Function of Tendons
    • -Connect muscle to bone
    • -Transmit mechanical force generated by muscle to bone to create joine movemt
  36. Innervation of Tendons
    • -Golgi Tendon Organ (GTO)
    • -Pain fibers (free nerve endings)
  37. Nutrient supply of tendons
    • -Limited vascular supply
    • -Synovial membrane (tendon sheath)
  38. Describe the Synovial Sheath
    • -2 layers: visceral and parietal
    • -Between the layers is a cavity for fluid
    • -Synovial sheath provides lubrication for tendons to slide within their fibrous sheath
  39. Function of Ligaments
    • -Connects bone to bone
    • -Controls and guides nomal movement of joints
    • -Limits excess motion
    • -Contain more elastic vs. tendons
  40. Innervation of Ligaments
    • -Proprioceptive fibers
    • -Free nerve endings
  41. Nutrient supply of ligaments
    Limited vasculature
  42. Aging effects on Loose CT
    • -↓ elasticity
    • -↓ hydrophilic capabilities
    • -↓ ROM
    • -↑ work to overcome inelasticity
  43. Aging effects on Dense Irregular CT
    • -↓ elasticity
    • -↓ hydrophilic capabilities
    • -↓ ROM
    • -↑ work to overcome inelasticity
  44. Aging effects on Dense Regular CT
    • -↓ size
    • -↓ protein synthesis
    • -↓ in tensile force
    • -↓ load to failure
    • -fiber degradation
  45. Effects of Immobilization of CT proper
    • -Contracture
    • -↓ in tensile force generation // ↓ load to failure
    • -↓ GAGs/H2O
    • -Cross-linking of collagen (reduces compliance)
    • -Synovial sheath becomes adherent on tendons; Adhesions prevents full ROM of affected joint
  46. Acute Activity effects on CT proper
    • -↑ temperature and ↑ in elasticity
    • -Micro tears (that are repaired); repair generates stronger and larger ligament/tendon
    • -Prevention of cross-links to maintain extensibility
  47. Chronic Activity effects on CT proper
    • -Hypertrophy of ligament/tendon - allows CT to transmit increased amounts of force
    • -↑ deposition of type I collagen, ↑ load to failure
    • -↑ ROM is stretched