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What are the functions of osteoprogenitor cells, osteoblasts, osteocytes, osteoclasts?
Osteoprogenitors differentiate into osteoblasts.
Osteoblasts: synthesize ECM; secrete vesicles that induce mineralization of the osteoid; lots of RER
Osteocytes: osteoblasts that become trapped in the matrix; maintain bone, stimulate osteoblasts and bone lining cells; can secrete or resorb small amounts of bone
Osteoclasts: bone resorption, very big and multinucleate
What is the difference between spongy (cancellous) and compact (cortical) bone?
Spongy: high strength to weight ratio; bone marrow is here.
Cortical: densly arranged, contains Haversian systems
Difference between woven and lamellar bone.
woven: early growth and development, lots of cells, disorganized collagen
Lamellar: almost the entire adult skeleton; collagen fibres are organized into layers called lamellae.
Label the architectural organization of bone.
Name the extracellular components of bone and their function.
- Organic (30% OF MASS):
- -mostly collagen (90%) (tensile strength)
- Inorganic (70% of Mass)
- -Mostly Hydroxyapatite intamitely attached to collagen (provides compressive strength)
The steps in endochondral ossification
- 1. Small ‘model’ of bone is formed from hyaline cartilage
- 2. Cartilage matrix calcifies and cells degenerate
- 3. Pericondrium transforms into a periosteum
- 4. A bony ‘collar’ forms
- 5. Blood vessels and mesenchymalcells invade
- 6. Osteoblast and bone marrow cell populations are established
- 7. Bone is formed on the remnants of calcified cartilage – to be later remodeled.
- 8. The initial ossification in the diaphysis is known as the primary centre
- 9. Secondary centres form within the epiphyses
- 10. Cartilage remains within the ‘growth plates’ (epiphyseal plates, physes) which facilitate continued longitudinal growth
What are the 4 functions of bone?
- 1) protection of organs
- 2) structural support
- 3) calcium and phosphorus reservoirs
- 4) Site for blood cell formation
How do bones mineralize at the osteoid?
- 1) osteoblasts secrete vesicles mineralization inhibitors
- 2) osteoblasts also secrete collagen
- 3) ions are elevated above the level of the osteoid
- 4) vesicles burst and allow mineralization of collagen to begin
Where does appositional growth happen in bones?
At the periosteum, the oseocytes here lay down bone that increases the diameter of long bones.
What is the difference between internal remodeling and external remodeling
internal: the internal turnover of bone
external: remodeling the extenal morphology of bone.