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| 2 mechanical functions of bone |
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Definition
rigid skeletal framework- support and protect body tissue
-levers that can produce body movement (Lever: relatively ridged object, rotate about an axis by the application of force)
-vascular +nerve supplied |
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Calcium carbonate and calcium phosphate (60-70%)
other minerals (f, mg, na)
collagen
water- 20-30% body weight= transport nutrients and transpt and stores mineral ions, contributes to bone strength
(these vary with age and health of the bone-demineralizes- and loss of collagen- inc porosity) |
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| what produces stiffness in bone |
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Definition
| produced by calcium carbonate and calcium phosphate |
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| point where permanent deformation occurs- moves from elastic to plastic region (will not return to original shape when stress is removed) |
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ability to resist pressing or squeezing force
-det by Ca carbonate and ca phosphate |
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ability to resist pulling or stretching force
-collagen |
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exhibiting diff mechanical properties in response to loads from different directions
-bone is strongest in resisting compression -weakest in shear |
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compact mineralized CT with low porosity found in the shafts of long bones
-stiffer- greater stress but less strain |
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| growth center of a bone that produces new bone tissue- part of normal growth process until closes in early adolescence or adulthood |
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| disruption in the continuity of a bone |
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| pressed together by a compressive load |
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| relatively rigid obj that may be made to rotate about an axis by the application of force |
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| specialized bone cells that build new bone tissue |
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| specialized bone cells that resorb bone tissue |
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| condition of reduced bone mineral density that predisposes the individual to fractures- bc decreased osteoid production aka bone material |
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| disorder involving decreased bone mass and strength with one or more resulting fractures |
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| double layered membrane covering bone- muscle tendons attach to outside layer and the internal layer is a site of osteoblast activity |
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Definition
ratio of stress to strain in a loaded material
(slope of stress-strain curve)--within the elastic region
-stress divided by the relative amount of change in structure shape |
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amount of deformation divided by the original length of the structure or by the original angular orientation of the structure
strain=change in length/original length |
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Term
| stress fracture aka. fatigue fractures |
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| fracture resulting from repeated loading of relatively low magnitude |
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progressive bone pathology associated with repeated loading
-microdamage-osteoclast resorb damage tissue, osteoblasts deposit new bone, if not enough time to repair=stress fracture |
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less compact mineralized CT with high porosity that is found in the ends of long bones and in the vertebrae
-more porous= smaller proportion of CaPO4 and CaCO3
-withstand greater strain less stress |
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Definition
functional unit= osteon/haversian system
osteon=central osteonic canal (with blood vessels parallel to long axis of bone) surrounded by lamellae (rings of matrix)
cells=osteocytes in spaces called lacunae
canaliculli- small channels radiating from lacunae to haversian canal |
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| epiphyseal plate- cartilaginous discs, near ends of long bones- grows inwards |
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periosteum innerlayer builds concentric layers of new bone tissue-
at same time bone is resorbed or eliminated within medullary cavity |
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bone responds to the stress placed on it and will remodel to withstand those stresses
-bone strength inc and dec as the functional forces on the bone inc and decrease |
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resorption of fatigue damaged older bone and subsequent formation of new bone
-new bone laid down at strain sties |
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When osteoblasts become trapped in the matrix they secrete, they become osteocytes.
-sensitive to changes in the flow of interstitial fluid through pores resulting form strain on bone
-boss of osteoblasts and clasts
25% of trabecular bone remodeled each year |
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Definition
| decrease in bone mass resulting from a predominance of osteoclast activity |
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| increase bone mass b/c high osteoblast activity |
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| ways to prevent/treat osteoporosis |
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Definition
early detect- easier to prevent than treat
-optimize peak bone mass in adolescence
-weight bearing PA
diet- ca vit D
factors can contribute:
excessive thinness, smoking, excessive protein/caffine, genetics |
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| disordered eating, young female atheletes, amenorrhea (ceesation period)= loss of estrogen=reduced bone density |
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| Characteristics of Female athlete triad |
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Definition
high incidence of fractures b/c osteoporosis
unsafe weight loss
disorded eating
other psychological variables
can be fatal! |
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| growth plate=cartilage cells wh gradually ossify to prod new bone- plate is weaker than surr bone- can terminate bone growth early |
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| how to increase bone density |
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-PA to stress bone and bone hypertrophy- need sufficient intensity, weight bearing
DYNAMIC not static loading
heavy weight low rep
varied movements=build overall density |
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| ability to control equilibrium |
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| area bound by the outermost regions of contact between a body and support surface or surfaces |
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point around which the mass and weight of a body are balanced no matter how the body is positioned
-balance point of a body as the sum of the torque about this point =0 |
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| pair of equal oppositely directed forces that act on opposite sides of an axis of rotation to produce torque |
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| dynamic equilibrium (D alembert's principle) |
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| concept indicating a balance b/w applied forces and inertial forces for a body in motion |
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| lever posn with the applied force and the resistance on opposite sides of the axis of rotation |
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| point of suppt or axis about which a lever may rotate |
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| simple machine consisting of a relatively rigid barlike body that may be made to rotate about an axis |
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| lever positioned with the resistance b/w the applied force and fulcrum |
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| resistance to disruption of equilibrium (both linear and angular acceleration) |
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| motionless state characterized by sum of vertical forces=0 horizontal forces=0 and net torque=0 |
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| lever posn with the applied force between the fulcrum and resistance |
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| rotaty effect of a force about an AOR measured as the product of force and the perpendicular distance b/w the forces line of action and the axis |
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| shortest (perpendicular) distance b/w a forces line of action and an AOR |
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| 4 ways to increase stability |
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Definition
increase mass
widen base of support
lower centre of gravity
bring line of gravity closer to the centre of bOS(base of suppt) |
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| 4 elements of balance and stability |
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Definition
mass
center of gravity
line of gravity
base of support |
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Definition
straight line from the body's centre of gravity to the middle of the earth- vector for weight
closer line to centre of BOS= more stability
(or shift toward on coming force- increase distance has to move) |
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Term
| when would you want to be unstable |
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Definition
| when athletes want to be ready to move in any direction, quickly as possible- lean with weight in desired direction of motion- LOG to edge of BOS |
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state of balance b/w two or more forces acting within or upon a body such that there is no change in the state of rest or motion of a body
- all forces are balanced= sum of forces and torques in all directions =0 |
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| motionless state characterized by sum of all forces and torques =0 |
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