Bones - Part 1 Flashcards
What is the extracellular component of bone?
Matrix
The Matrix is the extracellular component of bone. What are its 3 components?
- Osteoid
- Mineral
- Inorganic
What is the Osteoid component of the Matrix made of?
Type 1 collagen
Glycosamingoglycans
Osteopontin protein
What protein is included in the Osteoid component of the Matrix and what is its job?
Osteopontin protein
= Calcium Homeostasis
The Inorganic component of the Matrix is hard due to what material?
Hydroxyapatite (calcium and phosphorus)
What are the 2 histologic forms of bone?
Woven
Lamellar
Which histologic type of bone is produced rapidly and thus what is its correlating Collagen arrangement?
Woven
= Haphazard collagen arrangement => less structural integrity
Is woven bone normal in adults?
No
Which histologic type of bone is produced slowly and thus what is its correlating Collagen arrangement?
Lamellar
= Collage is parallel and stronger!
Which bone cells synthesize matrix and regulate mineralization?
Osteoblasts
What are Osteocytes?
Inactive osteoblasts with little cytoplasm
What bone cells control calcium and phosphate levels?
Osteocytes
How do Osteoclasts look and what is their job?
MULTI-nucleated macrophages
= Bone resorption
Long bones undergo what type of development?
Endochondral Ossification
Endochondral Ossification starts with what?
Cartilage mold (anlagen)
With Endochondral Ossification, how does Radial Growth occur?
New bone deposited beneath periosteum of Diaphysis (midshaft)
With Endochondral Ossification, how does Longitudinal Growth occur?
New bone deposited at the bottom of growth plates (epiphyses)
Flat bones undergo what type of development?
Intramembranous Ossification
Intramembranous Ossification
Mesenchyme directly ossified by osteoblasts
What type of growth is seen with Intramembranous Ossification?
Appositional Growth
= Direct deposit of new bone on surface
When does peak bone mass get achieved?
Early adulthood after cessation of skeletal growth
Usually, when does bone resorption > bone formation?
4th decade
What ligand/molecule do Osteoblasts express/secrete?
RANKL is expressed
OPG is secreted
What receptor do Osteoclasts express?
RANK
If the Osteoblast RANKL binds RANK on Osteoclasts, what will occur?
(+) NF-KB => (+) Osteoclasts => Bone Breakdown
If Osteoblast OPG binds RANK on Osteoclasts, what will occur?
Prevents RANKL from binding => Osteoclasts INHIBITED => Building bone
What (+) LRP5/6 receptors on Osteoblasts?
WNT
What occurs if WNT (+) LRP5/6 receptors on Osteoblasts?
(+) Beta-Catenin => Produces OPG
What can (-) the WNT/beta-catenin pathway in Osteoblasts?
Sclerostin
What 2 molecules are the main ones that balance bone formation and resorption?
RANK
WNT
What 3 molecules help to BUILD bone?
Estrogen
Testosterone
Vitamin D
What 3 molecules help to BREAKDOWN bone?
PTH
IL-1
Glucocorticoids
What bone cell does M-CSF activate?
Osteoclasts
What cascade does M-CSF activate that (+) Osteoclasts?
Tyrosine Kinase Cascade
