Bone Formation, Repair, Diseases Flashcards
Compare the 2 types of Ossification
What types of growth are involved in each?
Endochondral: Long bone formation from cartilage
Appositional Growth
Intra-membranous: Bone formation from Mesenchymal Stem Cell (MSC) clusters. Interstitial Growth
Explain Endochondral Ossification
- Begins as Hyaline cartilage
- Compact bone forms collar at sides of Diaphysis
- Central cartilage calcifies, Nutrient artery penetrates into middle of Diaphysis, forms Primary Ossification Centre
- Diaphysis becomes Cancellous, Calcified cartilage forms Epiphyseal Growth Plates, Secondary Ossification Centres form at epiphyses
- Epiphyses Ossify, Growth plates move apart to lengthen bone
- Growth plates replaced by bone, Hyaline Articular cartilage remains at end
Explain Intra-Membranous Ossification
- MSCs form cluster
- MSCs—> Osteoprogenitor cells—> Osteoblasts
- Osteoblasts lay down osteoid
- Osteoid mineralises to form SPICULES
- Spicules join to form TRABECULAE, which merge to form woven bone
- Trabeculae replaced by LAMELLAE of compact bone
What are the 2 steps in Bone Remodelling?
Osteoclasts make a wide tunnel in bone (Cutting Cone)
Osteoblasts make a smaller tunnel of cortical bone (Closing Cone)
Which 3 Cellular Factors affect Bone Stability and how?
Osteoclasts: Can act as osteoblasts AND osteoclasts
PTH—> Bone degradation by Osteocytic Osteolysis
Oestrogen-> Bone laid down
Osteoblasts: Increased activity by Oestrogen, Vitamin A
Osteoclasts: Increased activity by PTH
How does Vitamin D affect Bone Stability
- Produces Calcitriol used for Ca absorption
Describe 6 the steps of Fracture Repair
- Haematology forms
- Tissues die causing Inflammation
- Granulation tissue formation- New blood vessels in fibrin mesh
- Fibrocartilagenous (Soft Callus) formation- Fibroblasts lay down collage, Chondroblasts lay down Hyaline Cartilage
- Hard Callus- Ossification to make compact+cancellous bone
- Bone Remodelling
What causes increased Fracture Susceptibility in bone diseases?
Loss of mass of Trabecular bone
What is Osteogenesis Imperfecta also known as?
What is the Genetic Basis?
- Brittle Bone Disease
- Autosomal Dominant mutation in COL1A gene -> Incorrect collagen 1 production
What are 4 symptoms of Osteogenesis Imperfecta?
Blue Sclera
Incorrect tooth formation
Short stature
Weak Bones
Compare Rickets and Osteomalacia
- Who is affected
- Cellular basis
Rickets:
- Children
- Vit. D deficiency= Poor Ca mobilisation-> Poor mineralisation
Osteomalacia:
- Adults
- Vit. D deficiency= Poor Ca resorption-> Poor mineralisation
Compare symptoms of Rickets and Osteomalacia
R:
- Bowed legs
- Short stature
- Weak soft bones
- Painful to walk
O:
- Soft bones
- Muscle weakness
What is Achondroplasia?
- Genetic basis
- Cellular basis
- Which type of ossification is affected?
- Symptoms
- Autosomal dominant mutation in FGF3 Receptor gene
- FGF3R gene promotes Cartilage->Bone
- Endochondral
- Short stature, normal sized head and torso
What are the 2 types of Osteoporosis?
What are the 2 sub-types?
Primary and Secondary
Primary: Type 1 and Type 2
What does Osteoproris do to the bone?
What are 3 modifiable risk factors?
- Makes gaps in cancellous bone
- Don’t smoke
- Exercise regularly
- Increase Ca intake
