Bone and cartilage biology Flashcards
What are the components of bone?
Cells
Extracellular matrix
What are the four types of bone cells?
Osteoprogenitor
Osteoblasts
Osteocytes
Osteoclasts
What are osteoprogenitor cells?
Precurssor cells that differentiate into osteoblasts
What are osteoblasts?
Specialised fibroblasts that produce bone
Deposit osteoid
Control mineralisation
What are osteocytes?
Differentiated osteoblasts encased in bone they produced
Cell bodies lie in lacunae
Cell processes project through canaliculi and communicate via gap junctions
What are osteoclasts?
Develop from monocytes and have phagocytic mechanisms
Breakdown and reabsorb bone in remodelling
Large and multinucleated
Found only on bone surface - lie in howship’s lacunae
What makes up the extracellular matrix of bone?
Organic
- collagen
- proteoglycans
- non-collagenous proteins
Inorganic
- calcium hydroxyappetite crystals
List four diseases that affect collagen of bone
Scurvy
Osteogenesis imperfecta
Ehlers-Danlos syndrome
Chondrodysplasis
What is scurvy?
Collagen degradation as a result of vitamin C (Ascorbic acid) deficiency
What is the role of Vitamin C (Acsorbic acid)?
Makes hydroxylases
- required to make hydroxylysine and hydroxyproline
Why are hydroxylysine and hydroxyproline important?
Stabilise triple helix and are needed to stop collagen degradation
Which tissues does Scurvy affect?
All tissues containing collagen
i.e. bones, tendons, ligaments, blood vessels, skin
What is osteogenesis-imperfecta?
Mutation in gene coding for type I collagen
What is Ehlers-Danlos syndrome?
Mutation in gene coding for Type III collagen
What is chondrodysplasias?
Mutation in gene coding for Type II collagen
What is the function of non-collagenous proteins?
To control bone growth
What is the function of Calcium hydroxyappetite crystals?
Give ‘hardness’ and mechanical strength
What are the three stages of bone development?
- Osteoid
- Woven bone
- Lamellar bone
What is osteoid?
Unmineralised bone composed only of organic compounds (collagen etc.) secreted by osteoblasts
What is rickett’s / osteomalacia?
Dietery deficiency leading to defective mineralisation of bone => remains an osteoid
Rickett’s = osteomalacia in children
What is woven bone?
Calcium hydroxyappetite crystal outside collagen fibres
Randomly organised collagen fibres -> look woven
Secreted by “osteoblasts in a hurry”
What is lamellar bone?
Calcium hydroxyappetite crystals lie within collagen fibres which are arranged in lamellae
Lamellar bone is mechanically strong
What are the components of cartilage?
Chondrocytes
ECM rich in proteoglycans
What are the three types of cartilage?
Hyaline cartilage
Elastin cartilage
Fibrocartilage
