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Osteoblasts produce Type __ Collagen
1
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What controls normal OB differentiation?
cbfa (core binding factor alpha)
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__ downregulates osteoblasts
- PTH
- Glucocorticoids
- PG
- leptin
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__ upregulates OB
Estrogen
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__ & __ expressed during late stages of OB differentiation
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Describe blood supply to bone
- Outer 1/3: periosteal arteries
- Inner 2/3: nutrient arteries
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Which enzyme helps create Howship's Lacunae?
carbonic anhydrase
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OC stain for ___
tartrate-resistant acid phosphatase
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Half-life of OC's
10 days
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vitamin d requirements
- 400 IU
- 600 IU if >70yo
- (1mcg = 40 IU)
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How does PTH dosing have an anabolic effect on bone? resorptive effect on bone?
- Intermittent dosing
- Continuous dosing
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Origin of calcitonin?
clear cells of thyroid
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Ca requirements in kids, adult men, lactating women, pregnant women, post menopausal women with healing fx?
- kids 500-700mg/d
- adult men 750 mg
- lactating women 2000 mg
- pregnant women 1400 mg
- postmenopausal women 1500 mg
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Osteocytes:
- life span?
- stains for __?
- location?
- - decades
- - OC-specific monoclonal Ab
- - in lacunae within mineralized matrix of both cortical and lamellar bone
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Process of downregulating OC stimulation?
OPG binds to rank-L (on OB), which blocks rank-L to rank (on OC precursor)
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describe rank-rank-L relationship
- rank is receptor on OC precursor
- when rank-L (on OB) binds rank, OC precursor differentiates in OC
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Definition of osteoporosis
- decreased thickness & # of trabecular struts
- T score >2.5SD = osteoporosis (compares to normal young females)
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What is the Z score in osteoporosis?
- Z score is vs. own age-matched controls
- If >1.5 SD, look for secondary causes
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Target of bisphosphnates
farnesyl pyrophosphate synthase (FPPS)
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MOA of bisphosphonates
apoptosis
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Type I vs Type II senile osteoporosis
- Type I postmenopausal: trabecular bone, distal radius & vertebral fxs
- Type II senile: trabecular & corticla bone, hip & pelvis fxs, uncoupling of bone formation and resorption
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Painful hip, MRI with DIFFUSE osteoporosis. Dx? Tx? Px?
- Idiopathic Transient Osteoporosis
- unknown etiology affecting pregnant females or late-middle aged males
- Tx: protected WB +/- calcitonin
- Resolves with time
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Steps of Fx repair
- Inflammation
- Mesenchymal stem cells, fibroblasts
- Chondrocytes
- Soft callus
- Hard callus
- Remodeling
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Osteomalacia is a quantitative or qualitative problem?
Qualitative
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Types of ossification: (3)
- enchondral (bone replaces cartilage)
- embryonic (cartilage precursor converted to bone)
- intramembranous (no cartilage model, occurs with true rigid fixation)
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What is Groove of Ranvier? function?
supply chondrocytes to periphery of physis, allows widening of physis
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What is the perichondrial ring of LaCroix?
fibrous, support/anchors physis to diaphysis
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What type of collagen appears early in unstable fracture repair? Later?
Type I --> Type II
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BMP is part of the ___ family
TGF beta
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Host repair after AVN is _____
creeping substitution
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Name the physeal zones
- Reserve/Resting
- Proliferative
- Hypertrophic
- Metaphysis
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Reserve zone diseases
- "Reserve place kicker has good distance"
- pseudoachondroplasia
- kneist
- gaucher
- DD
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Diseases in proliferative zone
- GPA (big and small)
- Gigantism
- Achondroplasia
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Diseases in Hypertrophic zone
- MORE Sex Please
- Muchopolysaccharidoses
- Ostomalacia
- Rickets (provisional calcification zone)
- SCFE & Scurvy
- Physeal Fx
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How is regular SCFE different that endocrinopathy SCFE in terms of location of involvement in the physis?
- regular SCFE: Hypertrophic
- endocrinopathy SCFE: Metaphysis
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Weakest part of the physis?
hypertrophic
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