Bone Flashcards
Origin of osteoblasts
Undifferentiated mesenchymal stem cells
Multifunctional transcription factor that directs mesenchymal cells osteoblast lineage
RUNX2
Products of osteoblasts
OSTEOCALCIN Alkaline phosphatase Type I collagen Bone sialoprotein RANKL
Origin of osteoclasts
Hematopoietic cells in macrophage lineage
Actions of RANKL
Bind to receptors on osteoclasts
Stimulates differentiation into mature osteoclasts
Increase bone resorption
Action of bisphosphonates
Inhibit osteoclastic bone resorption
Types of bone
Normal
Lamellar
Cortical
Cancellous
Immature/pathologic
Woven
Origin of osteoclasts
Hematopoietic cells of macrophage lineage
Produced by osteoblasts, stimulates differentiation of osteoclasts to active mature osteoclasts
RANKL
Inhibits bone resorption by binding and inactivating RANKL
Osteoprotegerin
Directly inhibit osteoclastic bone resorption. Nitrogen containing (answer) are 1000 fold more potent
Bisphosphonates
Associated with osteonecrosis of jaw
Bisphosphonates
Bone matrix components
60% inorganic, 40% organic
Calcium hydroxyapatite majority of inorganic
Type 1 collagen majority of organic
Most abundant non collagenous protein in bone
Osteocalcin
Remodeling occurs in response to mechanical stress
Wolff’s law
Compressive forces inhibit growth, tension stimulates it
Heuter-Volkmann Law
Types of bone formation
Enchondral ossification
Intramembranous ossification
Appositional ossification
Bone formation. Bone replaces cartilage model
Enchondral ossification
Bone formation. No cartilage model. Aggregates of undifferentiated mesenchymal differentiate into osteoblasts which form bone
Intramembranous ossification
Bone formation. Osteoblasts lay down new bone on existing bone
Appositional ossification
3 stages of fracture repair
Inflammation, repair, remodeling
Fracture healing type in closed treatment
Periosteal bridging callus
Fracture healing type. Compression plate treatment
Primary cortical healing
Why do NSAIDS affect fracture healing?
COX-2 activity needed for normal enchondral ossification
properties of bone grafts
Osteoconduction - scaffold for bone growth
Osteoinduction- growth factors that stimulate bone growth (BMP in tibial fractures)
Osteogenic grafts
Highest compressive strength of any graft material
Calcium phosphate based grafts
Primary homeostatic regulators of serum calcium
PTH
1,25(OH)-vitamin D3
Bone mass peak age range
16-25
Most common cause of hypercalcemia
Malignancy
Definition of osteoporosis (WHO)
Lumbar bone density 2.5 or more SD less than peak bone mass of a healthy 25 year old
Tx of osteoporosis
Calcium supplements 100-1500mg/day
Bisphosphonates
