BMS09-1016 -Bone Growth, Modelling and Remodelling

Description

Define the terms ‘modelling’ and ‘remodelling’ as applied to the growth of bone. Understand why bones remodel. Explain the role of and interaction between osteoblasts and osteoclasts in bone remodelling. List the basic proteins/factors that control bone remodelling. Know Wolff’s Law and explain how mechanical forces can induce changes in bone architecture. Describe what may be learned about bone remodelling from a study of bone disease.
Evian Chai
Flashcards by Evian Chai, updated more than 1 year ago
Evian Chai
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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