Tissue Mechanics Flashcards
What are the 3 primary components of connective tissue?
- Fibrous proteins
- Ground substance
- Cells
What are 3 types of fibrous proteins?
Type I Collagen
Type II Collagen
Elastin
What are characteristics of type I collagen?
thick
stiff
binding
Where in the body is type I collagen found?
- Ligaments
- Tendons
- Fibrous joint capsules
What are characteristics of type II collagen?
- Thin
- Lower tensile strength
- Provides framework for other structures
- Provides internal strength
Where in the body is type II collagen found?
hyaline cartilage
What are characteristics of elastin?
- Small fibrils (larger than type II though)
- resists tension
- elastic properties
Where in the body is elastin found?
Walls of arteries
Lungs
Intestines
Skin
Other elastic tissues (hyaline cartilage and ligamentum flavum)
What is Ground substance made up of?
Proteoglycans (Glycosaminoglycans or GAGs)
Water
Solutes
GAG molecules have a negative charge. What important effect does this have on the ground substance of connective tissue?
They are hydrophilic and attract water into the tissue
What are the main functions of cells in connective tissues?
- Synthesize ground substance
- Tissue maintenance and repair
- Constant turnover
Do NOT influence mechanical properties
What are the 2 main cells in connective tissues and where can you find them?
Fibroblasts (ligaments, tendons, supportive CTs)
Chondrocytes (hyaline articular cartilage and fibrocartilage)
Where in the body can you find dense connective tissue?
Ligaments
Tendons
Perimuscular fascia
What is the composition of dense connective tissue?
HIGH type I collagen
LOW elastin
LOW fibroblasts
Does dense connective tissue have good or poor healing and why?
Poor healing due to low vascularity
How does dense connective tissue adapt to stress/strain?
Increased stiffness (increased collagen and GAG synthesis)
How is IRREGULAR dense connective tissue different from regular dense connective tissue?
Collagen is arranged irregularly (disorganized) in ground substance while fibers are arranged in parallel for regular
Where can you find IRREGULAR dense connective tissue?
joint capsules
T or F: Irregular dense connective tissue can resist forces from MULTIPLE directions
True.
Where in the body can you find REGULAR dense connective tissue?
ligaments
tendons
Do REGULAR dense connective tissues resist tension from multiple directions or in a longitudinal direction?
Longitudinal direction
What is the main purpose of ligaments
To constrain excess movement at bony articulations
What is a purpose of tendons?
To transmit large forces from muscle to bone
What are the 5 different modes of loading?
- Compression
- Tension
- Shear
- Torsion
- Bending
Define compression
Force applied perpendicular to the surface, pushes together
Define tension
Force applied perpendicular to the surface, pulling apart
Define Shear
sliding that occurs between surfaces
Define Torsion
Twisting around long axis
Define Bending
deformation occurs perpendicular to long axis, tension of convex side, compression of concave side
How will a material respond if it is strained within the elastic region of the stress-strain/load-deformation curve?
It will return to original shape after load is removed
How will material respond if it is strained within the plastic region of the stress-strain/load-deformation curve?
It will remain deformed after load is removed
What is the “yield point” of a load-deformation curve?
point where transition from elastic to plastic behavior occurs
What is the eq for stress and units?
Stress = force or load / area
N/m^2 = Pascals = Pa
What is the eq for strain and units?
Strain = Change in length (deformation)/ Initial length
%
What does the area under the curve of a stress-strain curve signify?
Energy
How do you determine stiffness of a tissue from a stress-strain curve?
Slope of linear/elastic region
Young’s modulus of elasticity: E = stress/strain
What is viscoelastic creep?
A deformation/strain response that occurs when tissue is exposed to a CONSTANT load/stress, where there is rapid initial deformation followed by slow deformation (creep) until equilibrium is reached
When you increase the loading rate of articular cartilage, how would the slope of the elastic region change? And what would that mean in terms of the stiffness of the tissue?
It would get steeper, therefore increased stiffness
What does a stress-relaxation curve demonstrate?
Stress response when exposed to a constant DEFORMATION
What is the general pattern of stress in a stress-relaxation curve, where a tissue is exposed to a constant deformation?
Rapid initial stress –> slow decreasing stress (required to maintain deformation)
What is the capacity for repair for articular cartilage?
Very limited
What are 3 functions of articular cartilage?
- Inc area of load distribution for jts
- Attenuate jt contact stress
- Provide a smooth, wear-resistant bearing surface
What are the 3 phases of healing?
- Inflammatory (1-10 days)
- Proliferation (3-30 days)
- Maturation/Remodeling (3-360 days)
Can physical activity/exercise mitigate the effects of aging on connective tissue and articular cartilage?
Yes!
If the goal of stretching is to increase flexibility (tissue length), you must be in the ___ region of the load-deformation (stress-strain) curve.
Plastic
The plantar fascia’s viscoelastic behavior means that it will:
Exhibit greater stiffness when loaded rapidly
Stress-relaxation in articular cartilage is important to use because:
When articular cartilage is deformed, stresses are attenuated through re-distribution of fluid
