L12- Bones Flashcards
What are osteoblasts?
Cells that form bone (produce collagen)
What are osteocytes?
A bone cell formed when an osteoblast becomes embedded in the material it has secreted
What are osteoclasts?
Multinucleated cells that resorb bone by engulfing it via integrin proteins, pumping in HCl to degrade and decalcify bone and degrade collagen
What are osteoblasts derived from?
Osteoblasts and chondrocytes are derived from mesenchymal stem cells/skeletal stem cells
Which transcription factors cause production of bone cells?
- Runx2, Osx= osteocytes
- Sox9/5/6= chondrocytes
- CEBPa, PPARg= adipocytes
- Myf5, MyoD= muscle myoblasts
What are osteoclasts derived from?
From HSC’s by following the macrophage lineage pathway
• Colony stimulating factor- macrophage CSF
• Rank ligand specifies it to osteoclast lineage
What is intramembranous ossification?
Bone formed directly from precursors e.g flat bones of skull, calvaria, clavicle
What is endochondral ossification?
Bone formed via cartilage intermediate e.g long
What is osteopetrosis?
Increased bone mass
What is osteoporosis?
Decreased bone mass
/bone loss
How does bone remodelling occur?
- Quiescence (no activity)
- Osteoclast recruitment leads to resorption by osteoclasts
- Osteoclast removal by apoptosis and osteoblast recruitment leads to reversal
- Formation of osteocytes
- Mineralisation
What are factors regulating bone remodelling?
- Systemic hormones e.g parathyroid hormone
- Growth factors/cyotkines e.g TGF-b, Wnt
- Local factors- PGE2
- Trasncription factors e.g Runx2
What is sclerostin?
An osteocyte specific gene related to mechanical loading
Secretion decreases with mechanical loading which leads to increased bone formation
