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Osteoblasts produce Type __ Collagen
What controls normal OB differentiation?
cbfa (core binding factor alpha)
__ downregulates osteoblasts
__ upregulates OB
__ & __ expressed during late stages of OB differentiation
Describe blood supply to bone
- Outer 1/3: periosteal arteries
- Inner 2/3: nutrient arteries
Which enzyme helps create Howship's Lacunae?
OC stain for ___
tartrate-resistant acid phosphatase
Half-life of OC's
vitamin d requirements
- 400 IU
- 600 IU if >70yo
- (1mcg = 40 IU)
How does PTH dosing have an anabolic effect on bone? resorptive effect on bone?
- Intermittent dosing
- Continuous dosing
Origin of calcitonin?
clear cells of thyroid
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
- life span?
- stains for __?
- - decades
- - OC-specific monoclonal Ab
- - in lacunae within mineralized matrix of both cortical and lamellar bone
Process of downregulating OC stimulation?
OPG binds to rank-L (on OB), which blocks rank-L to rank (on OC precursor)
describe rank-rank-L relationship
- rank is receptor on OC precursor
- when rank-L (on OB) binds rank, OC precursor differentiates in OC
Definition of osteoporosis
- decreased thickness & # of trabecular struts
- T score >2.5SD = osteoporosis (compares to normal young females)
What is the Z score in osteoporosis?
- Z score is vs. own age-matched controls
- If >1.5 SD, look for secondary causes
Target of bisphosphnates
farnesyl pyrophosphate synthase (FPPS)
MOA of bisphosphonates
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
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
Steps of Fx repair
- Mesenchymal stem cells, fibroblasts
- Soft callus
- Hard callus
Osteomalacia is a quantitative or qualitative problem?
Types of ossification: (3)
- enchondral (bone replaces cartilage)
- embryonic (cartilage precursor converted to bone)
- intramembranous (no cartilage model, occurs with true rigid fixation)
What is Groove of Ranvier? function?
supply chondrocytes to periphery of physis, allows widening of physis
What is the perichondrial ring of LaCroix?
fibrous, support/anchors physis to diaphysis
What type of collagen appears early in unstable fracture repair? Later?
Type I --> Type II
BMP is part of the ___ family
Host repair after AVN is _____
Name the physeal zones
Reserve zone diseases
- "Reserve place kicker has good distance"
Diseases in proliferative zone
- GPA (big and small)
Diseases in Hypertrophic zone
- MORE Sex Please
- Rickets (provisional calcification zone)
- SCFE & Scurvy
- Physeal Fx
How is regular SCFE different that endocrinopathy SCFE in terms of location of involvement in the physis?
- regular SCFE: Hypertrophic
- endocrinopathy SCFE: Metaphysis
Weakest part of the physis?