15. Bone Flashcards
What are the 4 main types of bone cells?
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
What 2 factors are contained within the extraceullar matrix of bone?
- Collagen
- Calcium hydroxyapatite
What are osteoblasts derived from?
Embryonic mesenchyme (osteoprogenitor cells)
What is the function of osteoblasts?
Secrete osteoid (unmineralised bone) made from type 1 collagen
What are osteocytes?
Inactive form of osteoblasts that become trapped in their own matrix
How do osteoblasts/osteoclasts connect to surrounding cells?
Via canaliculi
What are osteoclasts derived from?
Monocytes
Name a unique feature of osteoclasts.
Multinucleate cells
What is the function of osteoclasts?
Absorb bone
Where are osteoclasts located?
Sit in Howship’s lacunae
What factor secreted by osteoblasts regulates osteoclast activity?
RANKL
What are the 2 different types of bone by origin?
- Primary (woven)
- Secondary (lamellar)
What are the 2 different types of bone by mode of formation?
- Membranous
Endochondrial
What are the 4 types of bone by gross appearance?
- Spongy/cancellous
- Compact
- Osteons
- Appositional
Describe secondary bone.
- Forms as osteons
- Central Haversian canal containing blood vessels
- Surrounding concentric rings of lamellar bone with osteocytes
Which bones are formed via intramembranous ossification?
- Flat bones of the skull
- Some cortical bone shafts
Describe synovium.
- Lines the inside of the joint capsule
- 1-4 layers of synovial cells
- Variable shapes (squamous to cuboidal)
- Richly vascularised and highly innervated
Type A synovium are…
Phagocytes
Type B synovium are…
Rich in rER
Describe woven bone.
- Formed rapidly during new bone formation
- Mechanically weak
- Remodelled to stronger lamellar bone
