Basic Science Flashcards
Higher Young’s Modulus of elasticity means what?
MORE STIFFNESS
Young’s modulus is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression. Equal to the longitudinal stress divided by the strain.
What molecule or signal causes undifferentiated mesenchymal stem cells to differentiate into osteoprogenitor cells?
Runx2
What is the most specific marker of MATURE osteoblast?
Osteocalcin (stimulated by 1,25(OH) Vitamin D
What molecule activates osteoclasts?
RANKL
What molecule binds RANKL to limit its activity (inhibit osteoclasts)?
Osteoprotegrin
What molecule inhibits osteoblasts?
Sclerostin
- Sclerostin sequesters Wnts which are signaling molecules that promote osteoblast bone formation
- Sclerostin secretion is based on mechanical loading, decreased sclerostin in high areas of strain.
What antiseptics inhibit osteoblast bone formation?
Hydrogen peroxide, Betadine, Bacitracin
In relation to osteoblast activity - pulsatile PTH does what?
Stimulates osteoblast by producing Alk phos and Type I collagen
*High levels of PTH signal release of RANKL
In relation to osteoblast activity - 1,25(OH) vitamin D3 does what?
Stimulates osteoblast and leads to matrix and alk phos stimulation
In relation to bone activity - Estrogen does what?
Inhibits bone resorption through Adenylyl cyclase inhibition
In relation to bone activity - glucocorticoids do what?
Inhibit bone production
In relation to bone activity - Prostaglandins do what?
Stimulate bone resorption through Adenylyl cyclase
Osteocytes are former _______
Osteoblasts, which are surrounded by newly formed matrix
Osteocytes are connected and communicate via __________
Gap junctions
Osteocytes control extracellular __________ and ________
calcium, phosphorous
Osteocytes are stimulated by ______ and inhibited by_______
calcitonin (helps absorb extracellular calcium), PTH
Osteoclasts resorb bone by…
Binding _______
Increasing __________
Synthesizing__________
Binding bone surface through integrins (specifically αvβ3 or vitronectin receptor), having a “Ruffled border” to increase the surface area of resorption, synthesizing TRAP (tartrate-resistant acid phosphate - lowers pH utilizing carbonic anhydrase and thus increases solubility of hydroxyapatite crystals), cathepsin K, MMPs, lysosomal cysteine proteinases
RANKL is released by _________ and has a receptor on __________ and functions to _______. Lastly, RANKL is inhibited by _________.
osteoblasts, osteoclast precursor cells, activate them into mature osteocytes leading to bone resorption, osteoprotegerin (OPG)
Does activation of the following signaling molecules promote bone formation or resorption? RANKL Calcitonin IL-1 IL-10 Bisphoshonates 1,25 dihydroxy vitamin D Prostaglandin E2 IL-6 MIP-1A OPG (osteoprotegerin) Estrogen TGF beta
RANKL - resorption (binds to RANK receptor on osteoclasts)
Calcitonin - formation (inhibits osteoclasts by interacting with osteoclast surface receptors)
IL-1 - resorption (stimulates osteoclast differentiation)
IL-10 - formation
Bisphoshonates - formation
1,25 dihydroxy vitamin D - resportion (stimulates RANKL)
Prostaglandin E2 - resorption (activates adenylyl cyclase)
IL-6 resorption (myeoloma)
MIP-1A - resorption (myeoloma)
OPG - formation (sequesters RANKL)
Estrogen - formation (decrease RANKL)
TGF beta - formation
Wolff’s Law
Remodeling occurs in response to mechanical stress
(The compression side of bone is electronegative, stimulating osteoblasts
(formation))
Hueter-Volkmann law
Mechanical loading can influence the rate of growth.
-Compressive forces inhibit growth (gymnasts tend to be shorter); tension stimulates it
This type of remodeling occurs in small packets of cells
known as basic multicellular units (BMUs).
Endochondral bone formation occurs by _________ replacing _________. Two examples are…
bone replacing cartilage. Physeal growth (longitudinal growth) and fracture callous.
In endochondral bone growth this gene/protein promotes chondrocyte differentiation.
Sox-9