Bone

• About 50% of the dry weight of bone matrix is inorganic materials
• ORGANIC BONE MATRIX


  • Type I collagen (90%)
  • Small proteoglycans
  • Osteonectin: multiadhesive glycoproteins
  • Osteocalcin: Calcium binding proteins
  • Phosphatases from matrix vesicles promote calcification
• Compact Bone


  Dense area near the surface, 80% of total bone mass
• Cancellous Bone


  Deeper areas with numerous interconnecting cavities, 20% of total bone mass
• Compact Bone


  Cortical Bone
• Cancellous Bone


  Trabecular Bone

  Spongy Bone
• INORGANIC BONE MATRIX

  • About 50% of the dry weight of bone matrix is INORGANIC materials
  • (+) Calcium hydroxyapatite is most abundant
  • (+) bicarbonate, citrate, magnesium, potassium, and sodium ions
  • (+) noncrystalline calcium phosphate
• WOVEN BONE

  • Also knowns as Immature bone, primary bone, bundle bone
  • newly calcified
• LAMELLAR BONE

  • Also knowns as Mature bone, secondary bone
  • remodeled from woven bone
  • All normal regions of adult bone
• INTRAMEMBRANOUS OSSIFICATION

  • Osteoblasts

  differentiate directly from condensed sheets ("membranes") of embryonic mesenchymal tissue and begin secreting osteoid.
• ENDOCHONDRAL OSSIFICATION

  • Pre-existing matrix of hyaline cartilage is eroded and invaded by osteoblasts, which then begin osteoid production