Bone and Bone Injury/Repair Flashcards
What tcx factor directs mesenchymal cells to the osteoblast lineage?
RUNX2
What maintains the ionic milieu of bone?
“Entrapped cells” of osteoblasts = disruption of the active-lining cell layers activates these cells
Example of woven bone?
Embryonic skeleton, fracture callus
What produces RANKL? What expresses RANKL receptor?
Osteoblasts and tumor cells produce it, osteoclasts express receptor for it = stimulates differentiation into mature osteoclasts, increases bone resorption
What produces osteocalcin?
Osteoblasts
Intermittent (pulsatile) PTH releases stimulates what?
Osteoblasts
What does TNF-a do to osteoblasts?
Inhibits it
How does osteocalcin and PTH affect osteocytes?
Osteocalcin stimulates it, PTH inhibits it
Howship’s lacunae?
Where bone resorption occurs by osteoclasts
What does osteoprotegerin do?
Inhibits binding of RANKL = decreases bone resorption
How does calcitonin affect osteoclasts?
Inhibits it
What interleukin is found in membranes surrounding loose total joints?
IL-1 = potent stimulator of osteoclasts (IL-10 inhibits osteoclasts)
Bisphosphonates?
Inhibit osteoclasts, have direct anabolic effect on bone
Which bisphosphonates are assoc with osteonecrosis of jaw?
Non-nitrogen-containing bisphosphonates
Ortho implications of bisphosphonate use?
- Reduced rate of spinal fusion in animal model (recommend withhold prior to surgery)
- Safe for cementless hips and cemented knees, may decrease subsidence rate in acetabular component
- No data on fracture healing
Osteoprogenitor cells and strain conditions?
1) Low strain = osteoblasts
2) Intermediate strain = cartilage
3) High strain = fibrous tissue
Type of collagen in bone?
Type I
What is the most abundant noncollagenous protein in bone?
Osteocalcin = can be measured in serum or urine as a marker for bone turnover
Peizoelectric remodeling?
Remodeling occurs in response to electrical charge
1) Compression side = electronegative, stimulating osteoblasts
2) +ension side = electropositive, stimulating osteoclasts
Hueter-Volkmann law?
Remodeling occurs in small packets of cells known as basic multicellular units (BMUs) = compressive forces inhibit growth, tension stimulates growth
1) May play role in scoliosis and Blount’s dz
Bones with tenuous blood supply?
Scaphoid, talus, femoral head, odontoid
Long bones receive blood supply from 3 sources?
1) Nutrient artery = inner 2/3, high BP
2) Metaphyseal-epiphyseal system
3) Periosteal system = outer 1/3, low BP
Normal blood flow to bone? What happens to blood flow with a fracture or in immature bone?
1) Normal = centrifugal (inside to outside)
2) Fracture/immature bone = centripetal (outside to inside), periosteal system predominates
What is the major determinant of how well a fracture heals?
Bone blood flow
