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43 Cards in this Set
- Front
- Back
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Function of Connective Tissue
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-Covers organs - mechanical support
-Immune Defense - Blood -Storage of Water and Fat -Transportation - Tissue Fluid -Wound Healing -Control of Metabolic Processes in Other Tissues |
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Componenets of Connective Tissue
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Ground Substance and Fibers (Elastin and Collagen)
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Ground Substance Components
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Extra Cellular Matrix
Proteoglycans Glycoproteins |
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Function of Proteoglycans
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Hydration of Matrix
Stabilization of Collagen Networks Resist Compressive Forces |
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Function of Glycoproteins
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Linkage between components
-Smaller proteins and sugars |
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Properties of Collagen
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-Resists tensile loads
-Tripple helix within molecule -3 polypeptide chains folded to form a rope-like coil |
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Type I Collagen
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-Bones, ligaments, tendons, joint capsules
-Thick, rugged fibers gathered into bundles -Elongate very little with tension -Ideal for binding and supporting articulations |
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Type II Collagen
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-Articular Cartilage
-Thinner and Less Stiff -Flexible woven framework for maintaining general shape and consistency of structures such as hyaline cartilage -(Osteogenesis Imperfecta) |
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Connective Tissue Proper
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Loose and Dense
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Dense Connective Tissue
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-Regular - tendons and ligaments
-Irregular - Dermis of the skin |
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Supporting Connective Tissue
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Bone and Cartilage
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Specialized Connective Tissue
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Adipose and Hemopoietic Tissue
-Lymph and Blood |
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Functions of a Tendon
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Transmit Muscle Forces to Bone
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Structure of a Tendon
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-Parallel bundles of fibers between rows of fibroblasts
-Arise at the musculo-tendinous junction -Instert on Sharpey's Fibers (Osgood Schlatters Disease) |
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Functions of a Ligament
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-Stabilizes Joint
-Guides Motion -Prevents Excessive Motion |
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Structure of a Ligament
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Parallel fiber arrangement with extracellular ground substance
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Tensile Strain
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-Elongation per unit length of the material in response to tensile load
-Strain=(length after load - length before load)/Length before load -Measured in % |
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Tensile Stress
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Externally applied load per cross-sectional area
-Stress = F/A -F=Externally applied distraction force -A=Cross-sectional area of material tested -Measured in N/mm^2 |
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Stress-Strain Curve Regions
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-Toe Region
-Linear or Elastic Region -Plastic Region -Major Failure -Complete Failure |
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Linear or Elastic Region
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-Linear relationship between stress-strain
-Elongation is greater than in toe region -Stiffness increases -Microfracture begins -Young's Modulus of Elasticity -Remove Tensile force, return to pre-stressed length and shape |
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Young's Modulus of Elasticity
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-Steep Slope = high modulus, material is stiff or resistant to elongation
-Gradual Slope = low modulus, easily deformed (ligamentum flavum) |
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Rate of Loading in Elastic Region
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-Increased duration of elongation, increased time to recover to pre-stressed length
-Increase rate of loading, greater resistance to deformation - stiffness |
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Energy Within the Elastic Region
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-Not all energy applied is stored, some is lost as heat
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Hysteresis
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Loss of energy; difference between energy expended and energy regained
-More strain, but the same amount of force over time |
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Plastic Region
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-Progressive Failure - True tissue failure
-Yield point -Slope of curve decreased -Tissue remains permanently deformed but normal to the naked eye -Ligamentous sprain - joint laxity or instability |
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Failure
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Major failure - flattening of curve
Tendon or ligament is still intact Elongation without additional force |
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Complete Failure
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Ultimate stress and ultimate strain
Acute stress of more than 8% will lead to rupture |
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Biological Factors Affecting Biomechanical Properties of Tendons and Ligaments
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-Maturation and aging
-Hormones -Mobilization and immobilization -Diabetes mellitus and hemodialysis |
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Maturation and Aging on Tendons and Ligaments
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-During maturation, tensile strength, load to failure, elasitc modulus all improve
-With aging the tissue strength decreases |
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Hormones involved with tendons and ligaments
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Relaxin, Estrogen, Cortisol
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Mobilization and Immobilization with regards to Tendons and Ligaments
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-Remodel in response to mechanical demands
-Physical Training Increases Tensile Strength -Immobilizaiton Decreases Tensile Strength, More Elongation and Less Stiff |
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Cartilage Types
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Hyaline and Articular
Fibrocartilage |
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Properties of Cartilage
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-Smooth surface for articulating bones
-Devoid of blood, lymph and nerves -Mechanical Function |
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Mechanical Functions of Cartilage
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-Provides a weight bearing surface with low friction
-Helps to distribute the loads between bones |
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Composition of Cartilage
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-70 to 80% Water
-Proteoglycans (Protein core of Hyaluronic acid, chondroitin sulfate, keratan sulfate) -Collagen - Type II -Volume occupied by proteoglycan aggregates is limited by entangling collagen framework |
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Properties of Type II Collagen
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-Helical Proteins
-High Mechanical Strength -Increase use, Increase diameter -Decrease Collagen with an increase in age and immobilzation |
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Mechanical Properties of Cartilage
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Viscoelasticity and Creep
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Viscoelasticity
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-Mechanical behavior of a material when subjected to a constant load, its response varies with time
-Both fluid and solid-like properties -When compressed, cartilage becomes stiffer -(-) charged aggrecans are pushed together -Increased repulsive force adds to stiffness |
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Creep
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-A viscoelastic material is subjected to a constant load over time
-Rapid initial deformation -Slow (time-dependent) progressively increasing deformation -Fluid flows out of the cartilage from matrix -Permeability is highest near joint surface and lowest in deep zone |
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Lubrication
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Fluid Film Lubrication
Boundary Lubrication |
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Fluid Film Lubrication
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-Thin film of lubricant (synovial fluid) separates the bearing surfaces
-Fluid must be thicker than the roughness of the opposing surfaces -Depends on fluid viscosity, shape of gap, surface stiffness -Load on bearing surface is supported by pressure developed in the fluid film -Low Loads |
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Boundary Lubrication
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-Joint surfaces are protected by layer of boundary lubricant
-Prevents direct contact and eliminates most surface wear -Independent of lubricant viscosity -Lubricin - constituent of synovial fluid responsible for boundary lubrication -High Loads |
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Fibrocartilage
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-Histologically and embryologically related to articular cartilage
-Different biomechanical properties than articular cartilage -Ex: intervertebral discs, symphysis pubis |
