Skeletal Flashcards
How does cartilage receive nutrients?
Diffusion
What are the two means of cartilage growth and development?
Appositional growth
Interstitial growth
Describe appositional growth of cartilage
New cartilage is added to the surface of the older cartilage by chondroblasts from the deep perichondrium.
The chondroblasts then become more chondrocytic over time.
Describe interstitial growth of cartilage
New cartilage is formed within older cartilage by chondrocytes that divide and produce new matrix.
What are the three cartilage types?
Hyaline
Fibrous
Elastic
How does cartilage underpin long bone growth?
Hyaline cartilage present in the epiphysial plates of the long bones
New cartilage forms on the epiphysis side of the epiphysial plate and its ossifies into bone on the diaphysis side.
Describe how events at epiphysial plates lead to long bone growth?
Chondrocytes proliferate in the upper plate and arrange into vertical stacks, the cells hypertrophy lower down before they die and are ossified into the bone matrix.
What is bone tissue made of?
Tissue made up if several cells and connective fibres
What are functions of bone?
Load bearing
Protection (e.g. skull)
Attachment for muscles
Storage of calcium + phosphate
Contains bone marrow
What does bone consist of?
Cellular component and ECM mineralised by deposition of hydroxyapatite
What happens to the ECM in bone?
Mineralised by desposition of hydroxyapatite
2 features of bone
Resistant to tensile and compressive forces
What happens in rickets?
Lack of Vitamin D3 so failure to absorb calcium -bones bend
What happens as you add acid to bone, why?
Lose compressive strength
Becomes flexible as demineralised
What happens as you heat bone, why?
Collagen denatures and bone shatters when tensile force (but can deal with compressive forces)
What gives compressive strength to bone?
Hydroxyapatite crystals
What gives tensile strength to bone?
Collagen
What do calcium hydroxyapatite crystals attach to?
Collagen fibres
What 2 things does bone remodelling allow?
Bone shape maintenance during growth and fracture healing.
What are osteogenic cells derived from?
Mesenchyme
What are osteogenic cells?
Undifferentiated, pluripotent stem cells which can produce bone forming cells
Where are osteogenic cells found in adults?
Periosteum and endosteum in adults
Why are osteogenic cells important?
Remodelling, growth and repair of bones by providing new osteoblasts (when required)
What do osteoblasts do?
Secrete osteoid, make new bone
What happens to osteoid after secreted from osteoblasts?
Initially uncalcified but then mineralsed as it moves away from osteoblasts by deposition of hydroxyapatite
When are osteoblasts recruited?
When bone needs to grow
What do osteoclasts do?
Bone removal
What do osteoclasts allow?
Bone remodelling
Describe structure of osteoclasts?
Multinucleated marcophages
How do osteoclasts remove bone?
Acid and protease secretion, forming Howship’s lacunae
What are Howship’s lacunae?
Depression of bone surface where resorption has occured
How are osteoclasts anchored to bone?
Attach via integrins to matrix protein osteopontin in the bone matrix.
What do osteocytes do?
Preserve bone matrix, sitting in lacunae (surrounding bony matrix)
What are two types of bone formation?
Intramembranous and endochondral