Bone Growth &
Development
BPK 375
Bone Growth & Development
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When do the first bones ossify?
Which is the first bone to ossify?
Does exercise affect bone growth &
development?
10 weeks
gestation
16 weeks
gestation
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Osteocyte
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Osteoblast
–
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Immature bone cell that secretes organic
components of matrix
Osteoprogenitor Cell
–
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Mature bone cell that turns over bone mineral and
assists in repairs
Stem cells whose divisions produce osteoblasts
Osteoclast
–
Multinucleated cell that secretes acids and enzymes
to dissolve bone matrix
Intramembranous Ossification
Ossification of Mesenchymal Connective Tissue
Osteoblast
Osteocyte
Osteoclast
Growth of Skull
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Fontanelles
Suture Joints
Proportions
Growth of Vault of Skull
Jaw Growth
Acromegaly
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Oversecretion of
growth hormone
Prior to growth plate
fusion, causes
increased height
with normal
proportions
After fusion, causes
bone thickening and
connective tissue
overgrowth
Endochondral Bone Growth
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Short bones e.g. carpals
Articular
Cartilage
Compact
Bone
Periosteum
Haversian
System
Compact
Bone
Spongy
(Cancellous)
Bone
Yellow Bone
Marrow
Haversian System
Endochondral Ossification
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Chondrocytes at the center of
the cartilage model begin to
hypertrophy and disintegrate as
the matrix calcifies
Endochondral Ossification
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Blood vessels grow
around the edges of the
cartilage, and the
perichondrial cells convert
to osteoblasts. The shaft
of the cartilage then
becomes ensheathed in a
layer of bone
Endochondral Ossification
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Blood vessels penetrate
the cartilage and invade
the central region, growing
toward the epiphyses at
either end.
Fibroblasts migrating with
the vessels differentiate
into osteoblasts and begin
producing spongy bone
Endochondral Ossification
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Remodelling occurs as
growth continues,
creating a marrow cavity.
The bone of the shaft
becomes thicker, and the
cartilage near each
epiphysis is replaced by
shafts of bone.
Cartilaginous Growth Plate
Metaphyseal Reshaping
Time of Appearance of Primary & Secondary Ossification Centres
HAND Primary Centres
HAND Secondary Centres
Fuse
Fuse
FOOT Primary Centres
FOOT Secondary Centres
f.m. = fetal month, m = postnatal month, y = year
Hand most commonly used in
studies of child development
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Fairly representative of the total
maturational status of the skeleton
Greater number of ossification centres than
any other area in the arms and legs
Hand is an easy area to X-ray
Skeletal Age
 Greulich and Pyle
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radiographic Atlas of Skeletal Development
of the hand and wrist
American children
Reliability: 95% ±0.8 – ±1.0 yrs on repeat
ratings
 Tanner & Whitehouse
– Bone Specific Ratings
– English children
– Reliability: 95% ±0.6 yrs on repeat ratings
 American boys matured about 6 months earlier
than English children
Longitudinal series
of X-rays on a girl
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X-ray shows
bone not
cartilage
TW2
TannerWhitehouse
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Bone specific
ratings
Fulfill written
criteria
Assign score for
chosen stage
Bone Maturity Charts
Growth
Hormone and
Gonadotrophin
Deficiency
Bone Maturity Charts
Turner
Syndrome
Hippocrates
“That which is used
develops and that which is
not used wastes away”
Bone Development in response to Mechanical Forces
Lines of Stress in a metal
form loaded at its “head”
Lines of spicules of bone
seen in head of the femur
Exercise & Bone Growth
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HOWELL(1917) Dogs
 Retardation
in diameter growth in later
life
 Length & Basic Configuration
genetically determined
 Width influenced by exercise
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Some evidence for Longer more
Slender bones in sedentary animals
(Steinhaus;1933)
Exercise & Bone Growth
 KATO
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& ISHIKO (1966)
Children
Femur and epihyseal plates showed early closure
by several years in heavy workers.
Poor environment
Exercise and Bone Size
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BUSKIRK (1956)
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Nationally ranked tennis players.
Dominant hands & forearms had longer bones.
IVANITSKY - Soccer players
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Femur larger in diameter than nonathlete
Marrow cavity of tibia in runners active over five
years is often enlarged
Demineralization
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Bed rest causes a loss in bone mass.
Astronauts had decreased bone
mineralization after Gemini V and VI flights.
Exercises were arranged on Gemini VII and
deminerallization was reduced.
Bone Density
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DONALDSON (1970)
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30 week bed rest
Increased Calcium & Nitrogen in urine
Decrease 4.2% in total body calcium
Decreased bone mineralization
2hr/day quiet standing prevented the loss
Bone Density
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ISSEKUTZ (1966)
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WYSE & PATTEE (1954)
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3 hr quiet standing reduced calcium loss
4 hr supine exercise did not
Human paraplegics did not benefit from weight
bearing using a tilt table
EXERCISE causes increased bone
density
Dynamic Changes
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Woman with no teeth
How do braces work?
Why do teeth tend to return to their
original position after braces are
removed?
Genetic or Environmental
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Boy born without a tibia
Fibula surgically moved over
One year later fibula had taken
on the appearance of a tibia
Genetic or Environmental
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3 year old impaled by nail,
causing paralysis of one
leg
At time of injury normal hip
development
One year later drastic
changes