Bone Function Structure Mr Lee Van Rensburg Mr Staton Phillips 2014.
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Transcript of Bone Function Structure Mr Lee Van Rensburg Mr Staton Phillips 2014.
Integrins – attach to bone sealing spaceProduce H+ via carbonic anhydraseLower PH increases solubility of Hydroxyapatite Organic matrix resorbed by proteolysis
Osteoclasts
Osteoblasts
Osteoblasts affected by:
ILPDGFIDGFPTH1,25 Dihydroxy vitamin DGlucocorticoidsProstaglandinsOestrogen
Structure
10% CellsOsteoclastsOsteoblastsOsteocytes 90%Bone Lining cells
90% MatrixOrganic 40%Inorganic 60%
Organic (40%)
Collagen (90%)ProteoglycansNon collagenous matrix proteins
GlycoproteinsPhospholipidsPhosphoproteins
Growth factorsCytokines
Organic (40%)Collagen (90%)
Type - BONEPolypeptide triple helix Tropocolagen bond togetherForming fibrils
Woven Bone
LOCATION
Embryonic SkeletonNeonatal Skeleton Growing Metaphysis in under 4 yr olds
Near sutures of skullIn tooth socketsSome Tendon insertions
Callus
PROPERTIES
ISOTROPIC
SOFT
FLEXIBLE
RAPID DEPOSITION/TURNOVER
HIGH No. OF CELLS
uniform physical properties in all directions
Lamellar Bone
LOCATION
Throughout the adult skeleton
PROPERTIES
ANISOTROPIC
HARD
RIGID
SLOW DEPOSITION/TURNOVER
LOW No. OF CELLS
Properties differ based on the direction that is measured
Cortical BoneCompact
80% of the adult skeleton
20 times stiffer than cancellous bone
Lamellae in concentric rings aligned with lines of force
Complex arrangement of canals serving the lamellae(Haversian System)
Cancellous Bonetrabecular
20% of the adult skeleton
20 times less stiff than cortical bone
Lamellae also present aligned with lines of force
No Haversian System
McCarthy I. J Bone Joint Surg 2006:88:4-9
Bone circulation
Receives 5-10% of CO
Three sources1.Endosteal (nutrient artery)2.Metaphyseal epiphyseal system3.Periosteal system
McCarthy I. J Bone Joint Surg 2006:88:4-9
Bone circulation
1. Nutrient arteryEnters diaphysis to medullary cavityAscending and descending arteriolesCentrifugal high pressureInner 2/3rds of cortex
McCarthy I. J Bone Joint Surg 2006:88:4-9
Bone circulation
2. 2. Metaphyseal epiphyseal systemPeriarticular vascular plexus
eg. geniculate arteries
McCarthy I. J Bone Joint Surg 2006:88:4-9
Bone circulation
3. Periosteal systemlow pressure on periosteum Outer 1/3rd of cortex