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(13) Bone (Bone Function (Movement, Vascular, Chemical (Homeostasis),…
(13) Bone
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Clinical Implications
Paget's Disease
- Increased Osteoclast activity
Hyperparathyroidism
- Increased osteoclastic activity
Hyperosteoidosis
- Delayed mineralization
- Increase bone formation
Osteoporosis
- Uncoupling formation from resorption (unbalanced)
Modelling in teeth
- Facilitates tooth migration
- Facilitates function; Mastication
- Facillitates wound healing
Types of Bone
Compact Bone
- No spaces
- Not hollow
- Haversian System
Trabecular/Cancellous/Spongy
Woven Bone
- Immature
- Disorganized (Basket weave)
- Found in: Fetus
- Pathological: Fracture/Fibrous Dysplasia
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Cells
Origin
Mesenchymal
Osteoblast
- Location: Pre-existing mineralised surface (mineralisation front)
- Function: Formation of ECM of bone (Type 1 collagen & Protein)
- Type 1 Collagen (Deposited in concentric / parallel layers)
- Osteocalcin (most abundant non-collagenous protein)
- Akaline Phosphatase
- Proteoglycans
- Active: Secrete osteoid matrix (Unmineralized, soft, gel-like)
- Inactive: Lining cells
Osteocyte
- Can revert back to mesenchymal linages (Like all mesenchymal linage cells)
- Thin processes extend into canaliculi
- Intercellular communication (canaliculi)
- Regulate bone response to mechanical movement
Bone Lining Cells
- Can revert back to mesenchymal linages (Like all mesenchymal linage cells)
- Osteocyte on surface (Inner & Outer)
Adipose, Fibroblast, Chondrocytes, Muscles
Osteoblast Regulation
- Parathyroid Hormone
- Estrogen (Males have other hormones to prevent breakdown)
- Hormones/GF/exercise
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Periosteum
- Connective Tissue
- Inner cambium: Loose, Vascular, Osteogenic
- Outer fibrous: Less cellular, Contiguous with joint capsules
Terminologies
Remodeling/Turnover:
- Same area
- Resorption & Re-filling
- No net change in bone mass
Modelling:
- Different area
- Resorption & Apposition elsewhere
- Occurs in load changes