This site is 100% ad supported. Please add an exception to adblock for this site.

Kinesiology - Tissue Mechanics


undefined, object
copy deck
Function of Connective Tissue
-Covers organs - mechanical support
-Immune Defense - Blood
-Storage of Water and Fat
-Transportation - Tissue Fluid
-Wound Healing
-Control of Metabolic Processes in Other Tissues
Componenets of Connective Tissue
Ground Substance and Fibers (Elastin and Collagen)
Ground Substance Components
Extra Cellular Matrix
Function of Proteoglycans
Hydration of Matrix
Stabilization of Collagen Networks
Resist Compressive Forces
Function of Glycoproteins
Linkage between components
-Smaller proteins and sugars
Properties of Collagen
-Resists tensile loads
-Tripple helix within molecule
-3 polypeptide chains folded to form a rope-like coil
Type I Collagen
-Bones, ligaments, tendons, joint capsules
-Thick, rugged fibers gathered into bundles
-Elongate very little with tension
-Ideal for binding and supporting articulations
Type II Collagen
-Articular Cartilage
-Thinner and Less Stiff
-Flexible woven framework for maintaining general shape and consistency of structures such as hyaline cartilage
-(Osteogenesis Imperfecta)
Connective Tissue Proper
Loose and Dense
Dense Connective Tissue
-Regular - tendons and ligaments
-Irregular - Dermis of the skin
Supporting Connective Tissue
Bone and Cartilage
Specialized Connective Tissue
Adipose and Hemopoietic Tissue
-Lymph and Blood
Functions of a Tendon
Transmit Muscle Forces to Bone
Structure of a Tendon
-Parallel bundles of fibers between rows of fibroblasts
-Arise at the musculo-tendinous junction
-Instert on Sharpey's Fibers
(Osgood Schlatters Disease)
Functions of a Ligament
-Stabilizes Joint
-Guides Motion
-Prevents Excessive Motion
Structure of a Ligament
Parallel fiber arrangement with extracellular ground substance
Tensile Strain
-Elongation per unit length of the material in response to tensile load
-Strain=(length after load - length before load)/Length before load
-Measured in %
Tensile Stress
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
Stress-Strain Curve Regions
-Toe Region
-Linear or Elastic Region
-Plastic Region
-Major Failure
-Complete Failure
Linear or Elastic Region
-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
Young's Modulus of Elasticity
-Steep Slope = high modulus, material is stiff or resistant to elongation
-Gradual Slope = low modulus, easily deformed (ligamentum flavum)
Rate of Loading in Elastic Region
-Increased duration of elongation, increased time to recover to pre-stressed length
-Increase rate of loading, greater resistance to deformation - stiffness
Energy Within the Elastic Region
-Not all energy applied is stored, some is lost as heat
Loss of energy; difference between energy expended and energy regained
-More strain, but the same amount of force over time
Plastic Region
-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
Major failure - flattening of curve
Tendon or ligament is still intact
Elongation without additional force
Complete Failure
Ultimate stress and ultimate strain
Acute stress of more than 8% will lead to rupture
Biological Factors Affecting Biomechanical Properties of Tendons and Ligaments
-Maturation and aging
-Mobilization and immobilization
-Diabetes mellitus and hemodialysis
Maturation and Aging on Tendons and Ligaments
-During maturation, tensile strength, load to failure, elasitc modulus all improve
-With aging the tissue strength decreases
Hormones involved with tendons and ligaments
Relaxin, Estrogen, Cortisol
Mobilization and Immobilization with regards to Tendons and Ligaments
-Remodel in response to mechanical demands
-Physical Training Increases Tensile Strength
-Immobilizaiton Decreases Tensile Strength, More Elongation and Less Stiff
Cartilage Types
Hyaline and Articular
Properties of Cartilage
-Smooth surface for articulating bones
-Devoid of blood, lymph and nerves
-Mechanical Function
Mechanical Functions of Cartilage
-Provides a weight bearing surface with low friction
-Helps to distribute the loads between bones
Composition of Cartilage
-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
Properties of Type II Collagen
-Helical Proteins
-High Mechanical Strength
-Increase use, Increase diameter
-Decrease Collagen with an increase in age and immobilzation
Mechanical Properties of Cartilage
Viscoelasticity and Creep
-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
-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
Fluid Film Lubrication
Boundary Lubrication
Fluid Film Lubrication
-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
Boundary Lubrication
-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
-Histologically and embryologically related to articular cartilage
-Different biomechanical properties than articular cartilage
-Ex: intervertebral discs, symphysis pubis

Deck Info