bone and joint biomechanics Flashcards
functions of the skeleton
-support body weight
-movement
-protect critical structures
-store materials such as calcium
-blood cell production
major constituents of bone
-calcium carbonate + calcium phosphate (mineral)
-Collagen (organic)
-Water (25-30%)
Mineral part of bone
stiffness: ration of stress to strain
compressive strength: ability to resist pressing or squeezing forces
organic part of bone
tensile strength: ability to resist a stretching force
Classification of Bone Tissue
Cortical (compact)
Trabecular (cancellous)
Cortical
dense layer that makes up outer layer of bone
-particularly in long bones
-can withstand more stress but less strain
Trapecular
spongy bone with a honeycomb-like structure
-allows for a high strength to weight ratio
-shock absorbance
-looks like honeycomb
-can withstand more strain but less stress
stress
the amount of force or loading on a tissue/area
strain
the amount of deformation divided by the original length of the structure
Skeleton
177 are involved in movement; 206 in total
-axial: skull, spinal, column, sternum and ribs
-appendicular: upper and lower extremities, inclusion the pelvis and the scapula
types of bones
Long, short, flat, and irregular
Long bones
shaft or body with a medullary canal, and relatively broad, knobby ends
-have a diaphysis or cortical bone and epiphyses of trabecular bones
-FUNCTION: lever arms for movement
Long Bones Examples
arms: clavicle, humerus, radius, ulna, metacarpals, phalanges
legs: femur, tibia, fibula, metatarsals, phalanges,
short bones
relatively small, chunky, cube-like
-Filled with trabecular bone
-FUNCTION: shock absorption
short bone examples
carpals, tarsals, including the calcaneus
flat bones
flat and plate like
-FUNCTIONS: protection of internal organs and provide a broad surface for a muscle attachment
flat bone examples
superior, posterior portion of the skull, sternum, ribs, ilium, and scapula
Irregular bones
FUNCTION: unique structure for a unique function
irregular bone examples
facial bones, maxilla, mandible, vertebrae, sacrum, coccyx, patella
-sesamoid: bone embedded in a tendon
Trabecular alignment
trabeculae develop based on the stresses placed on a bone with respect to it’s axis
anisotropic
exhibits different mechanical properties in response to loads from different directions
-bone is strongest in resisting compression and weakest in resisting shear forces
types of bone cells
osteoblasts, osteoclasts, osteocytes
-maintain bone density
osteoblasts
“Bone Builders”
responsible for bone deposition
-recepters
-mechanorecepters and estrogen
-in the periosteum
-add bone to the external part of diaphysis
Osteoclasts
“bone crumblers”
responsible for bone resorption
-work steady throughout lifetime
-in the endosteum
-remove bone from the internal surface
-use HCL to dissolve bone mineral
-use enzyme to digest collagen
osteocyte
bone cell
-monitors health of bone matrix
bone remodeling
process of removing old bone tissue and depositing new bone tissue
-completly remodels every 2 years
-more force makes it go faster
-older you are gets slower
Epiphyseal plates (long bones)
cartilage between epiphysis and main part of bone where growth can occur
-2 in each long bone
when growth comes to an end
-chondroblasts divide less often and plate becomes thinner
-last long bone to grow is the clavicle
appositional growth
growth of a bone by addition of bone tissue to its surface
-all bones undergo this growth
wolff’s law
bone strength increases and decreases as the functional forces on the bone increase and decrease
-bone hypertrophy: increase
Bone atrophy: decrease
order osteoclasts work
resorption, reversal, formation, resting
