Why do we care about building strong bones?
- ______ vital organs
- all _____ attach to bones
- bone ______ where rbc are, reservoir of minerals
- reservoir of mums bone supports growth of ____ (can steal calcium if needed)
- lagrest source of calcium from mums ______ is from bone (donating skeleton)
The Skeleton
* _____ skeleton: vertebrae, sacrum, and other flat bones
* _______ skeleton: all long bones + the pelvis
- protect vital organs
- all muscles attach to bones
- bone marrow where rbc are, reservoir of minerals
- reservoir of mums bone supports growth of fetus (can steal calcium if needed)
- lagrest source of calcium from mums breastfeeding is from bone (donating skeleton)
The Skeleton
* Axial skeleton: vertebrae, sacrum, and other flat bones
* Appendicular skeleton: all long bones + the pelvis (focus primarily on)
Bone Mineral
* Inorganic components ~_____% of bone weight
* Mostly plate-like _________ crystals
- Inorganic Cal…. + phos…
Remainder of bone weight:
* ~____% organic matrix, collagen
* ~_____% water
- if all inorganic material would be very brittle and snap
- Inorganic components ~65% of bone weight
- Mostly plate-like hydroxyapatite crystals [ Ca 10(PO4)6(OH)2 ]
- Inorganic Calcium + phosphate
- Ca 10(PO4)6(OH)2
Remainder of bone weight:
* ~25% organic matrix, collagen
* ~10% water
Cortical Bone
* ~____%
* Also called ‘_______’ bone
* ______ part of long bones
* Dense, calcified tissue
* ______ support, ___ functions
Trabecular Bone
* ~____%
* Also called ‘_____’ or ‘cancellous’ bone
* _______ of long bones, vertebrae, ribs and iliac crest
* Inner network of thin, calcified trabeculae
* Active ______ role
Cortical Bone
* ~80%
* Also called ‘compact’ bone
* External part of long bones
* Dense, calcified tissue
* Structural support, protective functions
Trabecular Bone
* ~20%
* Also called ‘spongy’ or ‘cancellous’ bone
* Metaphyses of long bones, vertebrae, ribs and iliac crest
* Inner network of thin, calcified trabeculae
* Active metabolic role
Three Types of Bone Cells - look at slide 11
* Osteocytes: _____ bone cells
* Osteoblasts: bone _____ cells
* Osteoclasts: bone _______ cells
* Different ___________, different _____
Bone Processes
Bone cells influence bone structure by 3 processes:
* Gro…
* Mod..
* Remo…
- Osteocytes: mature bone cells
- Osteoblasts: bone forming cells (blast = build)
- Osteoclasts: bone resorbing cells
- Different appearances, different roles
Bone cells influence bone structure by 3 processes:
* Growth
* Modeling
* Remodeling
Bone Characteristics
- Basic form and function: ________ determined
- Final mass and architecture: ______ mechanisms sensitive to mechanical stimulation (e.g., bone-loading activity)
- Design: maximum ____ in response to weight-bearing stress, with minimal ____
- Wolff’s Law (1892): Bone will ______ structure, so as to withstand functional ____, and to ensure the ______ efficiency of locomotion
- Basic form and function: genetically determined
- Final mass and architecture: adaptive mechanisms sensitive to mechanical stimulation (e.g., bone-loading activity)
- Design: maximum strength in response to weight-bearing stress,
with minimal mass - Wolff’s Law (1892): Bone will optimize structure, so as to withstand functional loading, and to ensure the metabolic efficiency of locomotion
Bone Growth - look at slide 15
* The _______ of bone mass through bone formation during childhood and adolescence
* Changes in sh… and le…
* Under ______ control
* ______ following puberty, with epiphyseal closure (growth plate)
- no bone in between epiphyseal and tibia
- The accrual of bone mass through bone formation during childhood and adolescence
- Changes in shape and length
- Under endocrine control
- Ceases following puberty, with epiphyseal closure (growth plate)
Mechanisms Contributing to Long Bone Growth
- ________ Bone Formation
- Formation of ______ cartilage (1), which will later be replaced by bone
- Primary ______ center in the hyaline cartilage (3). Bone collar forms around the sides of the cartilage
- _____ (medullary canal) forms within primary ossification center (4)
- Secondary ______ center at the epiphysis (5)
- Epiphyseal growth plate (physis) eventually ____
- look at slide 18
- Endochondral Bone Formation (replacement of cartilage by bone)
- Formation of hyaline cartilage (1), which will later be replaced by bone
- Primary ossification center in the hyaline cartilage (3). Bone collar forms around the sides of the cartilage
- Cavity (medullary canal) forms within primary ossification center (4)
- Secondary ossification center at the epiphysis (5)
- Epiphyseal growth plate (physis) eventually fuses
Mechanisms Contributing to Long Bone Growth
2 key processes:
Long bone growth from childhood to maturity due mostly to new bone from
endochondral bone formation and modeling:
- ______ ________: replacement of cartilage by bone; responsible for growth in length
- ________ _____: direct production of bone without cartilage transition;
responsible for growth in girth
Long bone growth from childhood to maturity due mostly to new bone from
endochondral bone formation and modeling:
- Endochondral formation: replacement of cartilage by bone; responsible for growth in length
- Appositional growth: direct production of bone without cartilage transition;
responsible for growth in girth
Long Bone Growth: Epiphysis - look at slide 20 and 21
- Epiphysis expands _________ due to secondary ______ centre, further elongating the bone
- Layers of new bone ‘_____’ epiphysis upwards, _______ central
metaphyseal/diaphyseal regions of the bone - Growth in bone length = ________ and ______ expansion
- Cartilage is replaced by bone ______, which then ________
- Epiphysis expands circumferentially due to secondary ossification centre,
further elongating the bone - Layers of new bone ‘push’ epiphysis upwards, elongating central
metaphyseal/diaphyseal regions of the bone - Growth in bone length = metaphyseal and epiphyseal expansion
- Cartilage is replaced by bone matrix, which then mineralizes
Long Bone Growth: Epiphysis
- Zone 1: ______ Zone
- Cells are relatively ______
- Zone 2: ______ Zone
- Chondrocytes (_______ cells) rapidly divide and produce collagen
- Zone 3: _____ Zone
- Cells increase in size and organize into _____
- Zone 4: _____ Zone
- Chondrocytes stop producing ______ and die
- _____ occurs
- look at slide 23
Long Bone Growth: Epiphysis
- Zone 1: Resting Zone
- Cells are relatively inactive
- Zone 2: Proliferating Zone
- Chondrocytes (cartilage cells) rapidly divide and produce collagen
- Zone 3: Hypertrophic Zone
- Cells increase in size and organize into columns
- Zone 4: Terminal Zone
- Chondrocytes stop producing collagen and die
- Calcification occurs
Long Bone Growth Plate Characteristics
* Multiple growth plates at various sites of the body are growing __________,
at _______ rates! (e.g., vertebrae vs. long bones)
- Most long bones have at least ____ growth plates, but some only have ____ (e.g.,
growth plate at proximal and distal radius vs. 1 for phalanges/metacarpals) - At any point in time, the growth plates within a ______ long bone are growing at
_____ rates (e.g., Proximal vs. distal) - The growth plates above the water line are the fastest growing, slide 25
- Multiple growth plates at various sites of the body are growing simultaneously,
at different rates! (e.g., vertebrae vs. long bones) - Most long bones have at least 2 growth plates, but some only have 1 (e.g.,
growth plate at proximal and distal radius vs. 1 for phalanges/metacarpals) - At any point in time, the growth plates within a single long bone are growing at
different rates (e.g., Proximal vs. distal) - The growth plates above the water line are the fastest growing, slide 25
Long Bone Growth Plate Characteristics
* ______ of growth in length from 2 plates ~ equal ____ but becomes
more divergent with increasing age
- _______ growth in length due to damage to one growth plate will be partially offset by increased growth rate at other plate
Long Bone Growth Plate Characteristics
* Proportion of growth in length from 2 plates ~ equal prenatally but becomes
more divergent with increasing age
- Slowed growth in length due to damage to one growth plate will be partially offset by increased growth rate at other plate
Bone Modeling - look at slide 28 and 29
* Osteoblast and osteoclast activity at different ______ at the same or different
times
* Formation/resorption uncoupled, not _______ as in remodelling
- Alters ____ and mass
- Increases _____ strength
- Primarily in the _____ years
- Regional response to local _____ factors
Modeling: New bone formed by osteoblasts on outer (periosteal surface)
Modeling: Bone resorbed by osteoclasts on inner (endocortical surface)
- Appositional Bone Growth
- Osteoblast and osteoclast activity at different fronts at the same or different
times - Formation/resorption uncoupled, not sequential as in remodelling
- Alters shape and mass
- Increases bone strength
- Primarily in the growing years
- Regional response to local mechanical factors
Modeling: New bone formed by osteoblasts on outer (periosteal surface)
Modeling: Bone resorbed by osteoclasts on inner (endocortical surface)
- Appositional Bone Growth
Bone Modeling: Changes in Bone Size and Shape - slide 29 and 30
- As the ends of bone grow ________ (e.g., distal radius), formation and resorption modeling occur to preserve bone _____
- To preserve ______ thickness during growth, formation modeling occurs on the
______ surface and resorption modeling occurs on the endocortical surface
- As the ends of bone grow longitudinally (e.g., distal radius), formation and
resorption modeling occur to preserve bone shape - To preserve cortical thickness during growth, formation modeling occurs on the
periosteal surface and resorption modeling occurs on the endocortical surface
Bone Remodeling - slide 32 to 34
* Osteoblast & osteoclast activity on the same _____ (same site) at same time,
but in specific sequence
* _______ action (resorption followed by formation)
- Replaces ____ bone and adds ____ bone
- Temporary _____ between removal & formation (fragility)
- Predominant bone process modifying _____ in adults but occurs concurrently
with bone ______ during growth! - Happens throughout the lifespan
- Repairs every-day _____ on bone
- Osteoblast & osteoclast activity on the same front (same site) at same time,
but in specific sequence - Coupled action (resorption followed by formation)
- Replaces old bone and adds new bone
- Temporary lag between removal & formation (fragility)
Predominant bone process modifying mass in adults but occurs concurrently
with bone modelling during growth!
* Happens throughout the lifespan
* Repairs every-day stress on bone
Assessing Bone During Growth
- three types
Need a technique that can measure: - Amount of bone _______: BMC, BMD
- Shape/distribution of bone
- Biomechanical _____ of bone
- With minimal _____ risk, high ____, and in lots of people
- DXA, pQCT, HR-pQCT
- Amount of bone mineral: BMC, BMD
- Shape/distribution of bone
- Biomechanical strength of bone
With minimal health risk, high precision, and in lots of people
Clinical Research: DXA
Can measure:
* Bone _____, areal bone mineral _____ (aBMD)
* Whole body, clinical sites (hip, spine)
Cannot measure:
* 3D shape of bone; ________ BMD
* Micro….
Attenuation of X-ray beams ~ tissue density
* More dense ______ (e.g., bone) ‘attenuates’ X-ray
* Low dose _____ risk
* Highly ____
- Applied extensively to growth studies over past 40 years!
Can measure:
* Bone mass, areal bone mineral density (aBMD)
* Whole body, clinical sites (hip, spine)
Cannot measure:
* 3D shape of bone; volumetric BMD
* Microarchitecture
Attenuation of X-ray beams ~ tissue density
* More dense tissue (e.g., bone) ‘attenuates’ X-ray
* Low dose radiation risk
* Highly accurate
- Applied extensively to growth studies over past 40 years!
Research Only: High-Resolution pQCT (HR-pQCT) - look at slide 38 and 39
- Separates Trabecular & ______ bone
- Cross-sectional area
- Volumetric bone _____
- Bone micro……
- Estimates bone _____
Bone Mineral Accrual in Healthy Children: Observational Studies
University of Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS)
* 7-year _________ study
* what type of scan
* Normative values for bone mineral content (BMC) and ____ density (aBMD)
- Separates Trabecular & Cortical bone
- Cross-sectional area
- Volumetric bone density
- Bone microarchitecture
- Estimates bone strength
Bone Mineral Accrual in Healthy Children: Observational Studies
University of Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS)
* 7-year longitudinal study
* DXA
* Normative values for bone mineral content (BMC) and areal density (aBMD)
Bone Mineral Accrual - look at slide 41
* Found ______% of total bone mineral accrued in the two adolescent years
surrounding peak bone mineral content velocity (PBMCV)
Total Body BMC Velocity Curve:
Boys:
* Age of PHV: _____
* Age of PBMCV: 14_____
* Age of increased fracture: _____ to ____
Girls:
* Age of PHV: ____
* Age of PBMCV: _____
* Age of increased fracture: _____ to _____
- Found 26% of total bone mineral accrued in the two adolescent years
surrounding peak bone mineral content velocity (PBMCV)
Total Body BMC Velocity Curve:
Boys:
* Age of PHV: 13.4
* Age of PBMCV: 14.1
* Age of increased fracture: 13.5 to 14.5
Girls:
* Age of PHV: 11.8
* Age of PBMCV: 12.5
* Age of increased fracture: 11.5 to 12.5
Bone Mineral Accrual
* Age at PBMCV after ______
* Age at PBMCV is later in….
* Magnitude of PBMCV is _____ in boys
* Sex difference in total BMC favoring males ~ ___ years onwards
Total Body BMC Velocity Curve:
Boys:
* Age of PHV: _____
* Age of PBMCV: 14_____
* Age of increased fracture: _____ to ____
Girls:
* Age of PHV: ____
* Age of PBMCV: _____
* Age of increased fracture: _____ to _____
- Age at PBMCV after APHV
- Age at PBMCV is later in boys vs. girls
- Magnitude of PBMCV is greater in boys
- Sex difference in total BMC favoring males ~ 13 years onwards
Total Body BMC Velocity Curve:
Boys:
* Age of PHV: 13.4
* Age of PBMCV: 14.1
* Age of increased fracture: 13.5 to 14.5
Girls:
* Age of PHV: 11.8
* Age of PBMCV: 12.5
* Age of increased fracture: 11.5 to 12.5
Peak Bone Mineral Accrual
Saskatchewan PBMAS: Total body Bone Mineral Content (g)
- Peak bone mass occurs near end of ______ decade or early in the _____ decade of life (early 20’s) SLIDE 43
Peak Bone Strength
UBC Healthy Bones Study: Tibia bone strength
* Peak bone strength occurs ~ _____ years after APHV (near end of ____ decade or early in the _____ decade of life)
Saskatchewan PBMAS: Total body Bone Mineral Content (g)
- Peak bone mass occurs near end of second decade or early in the third decade of life (early 20’s) SLIDE 43
Peak Bone Strength
UBC Healthy Bones Study: Tibia bone strength
* Peak bone strength occurs ~ 8 years after APHV (near end of second decade or early in the third decade of life)
Bone Structure and Strength Accrual During Growth - slide 45
* Boys’ bones tend to be larger and stronger than girls’
* Boys have greater bone _______ and greater medullary canal area, which
places bone mass further from the neutral axis, leading to increased bone ______
- Increases in bone area and ______ cavity in girls vs. boys
Bone Mass Across the Lifespan
* Stage 1: bone accrual is ______ than bone loss
* Stage 2: bone accrual _____ bone loss (peak bone bass)
* Stage 3: bone accrual is _____ than bone loss
- Boys’ bones tend to be larger and stronger than girls’
- Boys have greater bone area and greater medullary canal area, which
places bone mass further from the neutral axis, leading to increased bone
strength - Increases in bone area and marrow cavity in girls vs. boys
Bone Mass Across the Lifespan
* Stage 1: bone accrual is greater than bone loss
* Stage 2: bone accrual equals bone loss (peak bone bass)
* Stage 3: bone accrual is less than bone loss
Bone Across the Lifespan
* Adolescence characterized by rapid ____ growth and increases in _____
* Aging characterized by thinning of _____, reduced bone _____ and strength
Determinants of Bone Accrual
Dietary Factors:
* Calc…..
* Vitamin ___
- ______ factors
- Gene…
- ______ loading
Other factors:
* Med…
* Dis…
Bone Across the Lifespan
* Adolescence characterized by rapid bone growth and increases in strength.
* Aging characterized by thinning of cortex, reduced bone density and
strength
Determinants of Bone Accrual
Dietary Factors:
* Calcium
* Vitamin D
- Endocrine factors
- Genetics
- Mechanical loading
Other factors:
* Medications
* Disease
Darwin on Bone (1859)
“… the ______ duck’s bones of the wing weigh less and bones of the legs more in proportion to the whole skeleton, than do the same bones in the _____ duck, and the change may be safely attributed to the ______ duck flying less and walking more than its wild parents.”
Wolff’s Law
* Bones will ______ to the degree of mechanical loading
* An increase in loading will cause the architecture of the internal, ______ bone
to strengthen, followed by the strengthening of the ______ bone
Darwin on Bone (1859)
“… the domestic duck’s bones of the wing weigh less and bones of the legs more in proportion to the whole skeleton, than do the same bones in the wild duck, and the change may be safely attributed to the domestic duck flying less and walking more than its wild parents.”
Wolff’s Law
* Bones will adapt to the degree of mechanical loading
* An increase in loading will cause the architecture of the internal, trabecular bone
to strengthen, followed by the strengthening of the cortical bone
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Intro to Growth32
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Study design14
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Growth charts part 110
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Growth charts part 224
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Post natal growth (after midterm)27
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Weight-neutral approaches to health (Guest lecture)1
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Prenatal part 122
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Prenatal part 226
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Prenatal part 315
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Sex Determination11
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Endocrine23
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Biological Maturation35
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Skeletal System30
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Growth Injuries13
