22147203
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
over 4 years ago
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| Question | Answer |
| When does bone MODELLING occur? What does it do? | In the growing skeleton (eg. in children or during development) It shapes the skeleton |
| Bone modelling is net.... where osteoclastic bone formation ... bone reabsorption | Bone formaton > is more than |
| When does bone remodelling occur? For what 3 reasons? | In adults 1. Calcium homeostasis 2. Skeletal homeostasis 3. Adaptation to mechanical forces |
| When bone reabsorption>formation...occurs When bone reabsorption<formation...occurs | 1. Osteoporosis 2. Osteopetrosis |
| In bone remodelling, how does bone mass change? Bone formation is .... to Bone reabsorption | No net change in bone mass equal, only occurs where there is bone reabsorption |
| What type of bone does 80% of bone remodelling occur in? | Trabecular bone |
| What is the process of Activation-Resorption-Formation (ARF)? | 1. Osteoclast precursors recruited to lining cells 2. Multinucleation 3. Preosteoclasts create sealing zones 4. Osteoclasts pump H+/Cl- into sealing zones 5. Osteoclasts die 6. Osteoblasts proliferate 7. Matrix made at reversal line, osteoid (unmineralised bone) forms 8. Mineralisation 9. Osteoblasts become osteocytes in lining cells or lining cells |
| What is Howship's Lacunae? | The sealing zone wherein Osteoclasts pump in H+/Cl- to degrade bone |
| What happens at the reversal line? | Osteoclasts die and are replaced by osteoblasts, which start secreting matrix |
| How does bone remodelling occur at the growth plate/metaphysis? Which bone is formed first: woven or lamellar? | 1. Cartilage is calcified for osteoclasts to reabsorb 2. First cycle is when when cartiledge is reabsorbed to form woven bone 3. Woven bone reabsorbed to form lamellar bone |
| Does reabsorption happen at the top or bottom of the growth plate/metaphysis? | Bottom Formation occurs at the top |
| What factors affect Bone Remodelling other than mechanical stress? (4) | 1) Systemic hormones - Parathyroid hormone (Increase plasma Ca2+) - Tri-iodothyronine - Growth hormone - Estrogen (lower bone breakdown) 2) Growth factors/cytokines - Bone morphogenetic proteins - Haematopoietic cytokines 3) Local factors - Prostaglandins 4) Nuclear transcription factors - Nuclear genes - Mission control - It instructs what to do (differentiate, proliferate, die) |
| According to Wolff's Law what determines the 3D structure of bone (mass/structure)? | Mechanical stress; bone is laid out in areas of maximal tensile stress |
| How does bone sense mechanical stress? | Osteocytes are mechanoreceptors |
| What are three bone diseases? | 1. Fractures 2. Osteoporosis 3. Paget's Disease |
| What is an example of mechanical loading in dentistry? | Teeth moving in orthodontics |
| What is the difference between Primary Spongiosa & Secondary Spongiosa | 1. Primary spongiosa is made of woven (immature) bone 2. Secondary spongiosa is made of Lamellar bone (closer to remodelling so closer to metaphysis) |
| What is Paget's Disease? | - Too much osteoclasts - Osteoblast cannot synthesise enough matrix - Abundance of osteoid and woven bone |
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