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→Composition of Bone
==Composition of Bone==
==Composition of Bone==
Bone is comprised of:
*Matrix:
**Organic component: "Collagen I", which resists tension
**Bone-specific proteins: Osteonectin, Osteopontin, Osteocalcin
**Inorganic component: Calcium, Phosphorus, Bicarbonate, Citrate, Potassium, Magnesium, Sodium, which provide rigidity
*Cells:
**'''Osteoblasts''': single layer of cuboidal cells which synthesize bone extracellular matrix (ECM)
**'''Osteocytes''': osteoblasts embedded in their own matrix; reside within '''lacunae''' and are interconnected via channels forming '''canaliculi'''
***'''Canaliculi''' create connections to form a huge neural-like junctional organization
**'''Osteoclasts''': giant (multinucleate monocytes) cells which act to resorb bone ECM
All mammalian bone is organized as lamellated sheets:
*'''Cortical (compact) bone'''
*'''Cortical (compact) bone'''
**Sheath covers external surface of long bone, thicker in shaft and thins over epiphyses
**Sheath covers external surface of long bone, thicker in shaft and thins over epiphyses
**Comprised of thin lamallae in a series of concentric tubes arranged around small central canals (collectively known as an '''osteone''')
**Comprised of thin lamallae in a series of concentric tubes arranged around small central canals (collectively known as an '''osteone''')
*'''Cancellous (spongy) bone'''
*'''Cancellous (spongy, or trabecular) bone'''
**Forms the hematopoeitic center of epiphyses
**Forms the hematopoeitic center of epiphyses
**Stacks of parallel or concentrically stacked sheets arranged as rods, plates, and arches
*'''Medullary Cavity and Cancellous Interstitium''': bone marrow storage and production
*'''Medullary Cavity and Cancellous Interstitium''': bone marrow storage and production