What are the 2 incremental lines in bone?
- Reversible (where the bone has been resorbed and reversed)
- Smooth (Marks a former surface of bone deposition)
What is the Osteoid?
where active bone formation is occurring
Describe the properties of osteoblasts
- Mesenchymal origin
- mineralise organic matrix
- incorporated into the bone as osteocytes
Describe the properties of Osteocytes
- Mesenchymal in origin
- Lie within the bone
- These are the most abundant cell within bone
- Communicate via canaliculi
- Detect strain in the bone
Describe the properties of osteoclasts
- Hemopoietic in origin
- Multinucleated
- Resorb bone
- Ruffled border
- Pumps acid to degrade bone
What are bone lining cells?
- A layer of flattened cells that occur when bone is in neither the formative or resorbitive state
How is bone organised?
- Cancellous bone
- Compact bone
What is cancellous bone?
- Lamella from trabeculae
- Lattice arrangement
What is compact bone?
- At external and internal surfaces of the lamella
- surrounding bony surfaces
- Dense solid mass
what is combination bone?
- A combination of both cancellous and compact bone (providing maximum strength at minimum skeletal weight)
What percentage of bone is inorganic?
60% hydroxyapatite crystals
What percentage of bone is organic?
25% type 1 collagen and protein
what percentage of bone is water?
15%
What is included in the organic matrix of bone?
- 90% collagen fibres
- proteins: proteoglycans, glycoproteins, osteocalcin, growth factors, serum proteins
where do sharpeys fibres occur in the bone?
- pale zone (unmineralised)
- bundle bone (extending deep into the alveolar bone)
- Osteoblasts (lie between the periodontal ligament and the alveolar bone)
What are the stages of bone remodelling?
- Resting
- Resorption
- Reversal
- Formation
What occurs during the resting stage of bone remodelling?
- Formation ceases following mineralisation
What occurs during the resorption stage of bone formation?
- Migration and activation of osteoclasts causing bone resorption
What occurs during the reversal stage of bone formation?
- Cessation of resorption and the disappearance of osteoclasts by apoptis or migration
what occurs during the formation stage of bone formation?
- Osteoblast recruitment
- formation of new bone
