Quiz 1.3 Flashcards
Functions of Bone
Protect vital organs
Support soft tissue
Produce RBCs
Reservoir for minerals (Ca)
Attachment site for skeletal muscle
System of machines to receive muscle torque and make movement
Osteon
Allow cortical bone to remain rigid while receiving nutrients and removing waste
One “group of circles” in bone histology
Bones comprised of
Bone cells and ECM
Osteoblasts
Form bone matrix
Osteocytes
Maintains bone tissue
Osteoclasts
Resorbs bone
Osteoprogenitor cells
Stem cells
ECM composed of
Collagen fibers, inorganic materials
Factors that influence mechanical properties of bone
Structure
Geometry
Mode of loading
Rate of loading
Frequency of loading
Muscle activity
Age
Structure
Mineral (largest)
-Ca & P, compressive strength
Collagen, water (middle)
-tensile strength, some flex
Ground substance
-Gel surrounding collagen, compressive strength
Geometry
Cross sectional area is proportional to failure point
Increase A = increase strength
Polar moment of inertia
Polar moment of inertia
Distribution of bone tissue around neutral axis
Mass away from axis = increas PMI
Close to axis = decrease PMI
More dense = handle more force
Mode of loading
Anisotropic: stiffness and strength depend on mode
Failure highest during Compression, then tension, then lowest at shear
Why is failure lowest with shear
Because smallest SA along shear plane, bones not made for shear load
Rate of loading
Visco-eleastic: Stiffness and strength depends on speed of load
High load rate: Increase stiff, increase failure point (increase E storage)
Decreased loading rate
Slower app of force; cracking with NO fragments, little/no soft tissue damage
Increased loading rate
Faster app of force; comminuted with displaced fragments, extensive soft tissue damage
Viscoelasticity
Materials behave in elastic and viscous manners with different rates of loading
Higher loading rate, increase stiff
See graph
Frequency of loading
Bones fatigue/weaken during repeated loading because fatigue process out paces repair
Factors: magnitude of load, number of load apps, number load apps in given time
See graph of injury
Fatigue fractures
Stress fracture
High load, few reps
low load, many reps
Muscle activity
Muscles may produce tensile or compressive stresses on bone, offset mechanical stress
Aging
Decrease bone density with age, collage and mineral content decrease so does bone mass and size (Decrease stiff and strength)
Bone remodeling
Increase bone density; alters size, shape, and structure based on imposed mechanical demands
Affected by activity level and implants
Wolff’s law
Bone tissue is gained/lost depending on level of stress sustained.
Increase mechanical stress, increase bone tissue production
