27: Physiology Of Bone Flashcards

1
Q

Function of organic components of bone

A

Contributes to flexibility and tensile strength of bone

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2
Q

Seven organic components of bone

A
  1. Collagen
  2. Osteonectin
  3. Osteocalcin
  4. proteoglycans
  5. sialoproteins
  6. osteopontin
  7. thrombospondin
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3
Q

major organic component of bone

A

collagen

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4
Q

osteonectin and osteocalcin: 2 functions

A

hydroxyapatite crystallization, Ca binding

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5
Q

what do sialoproteins, osteopontin, and thrombospondin do?

A

mediate osteoclast adhesion to bone surface

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6
Q

proteoglycan function

A

bind GFs

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7
Q

two main inorganic bone components

A

hydroxyapatite, mineral salts (Calcium phosphate, calcium carbonate, K, Mg)

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8
Q

osteocyte function

A

regulation of osteoblasts and osteoclasts by releasing paracrine factors

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9
Q

Major stimulator and inhibitor of osteoclast differentiation

A

Stimulator: RANKL
Inhibitor: OPG

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10
Q

TGF-B: two functions

A
  1. Osteoblast stimulation

2. Increased OPG production

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11
Q

BMP function

A

Potent osteoblast inducer

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12
Q

rhBMP-2

A

Clinical use for fracture healing and spinal fusion

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13
Q

RANKL function

A

Osteoclast activation

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14
Q

Osteoprotegerin (OPG)

A

Mock receptor for RANKL -> prevents osteoclast activation

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15
Q

FGFs (fibroblast GFs): two functions

A
  1. Osteoblast proliferation

2. Enhance callus formation during fracture repair

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16
Q

FGF-2

A

Stimulates angiogenesis during fracture repair

17
Q

IGFs (insulin-like GFs)

A

Increase bone collagen matrix synthesis

18
Q

What stimulates IGFs?

A

GH

19
Q

PDGF (platelet-derived GF)

A

Increases collagen synthesis

20
Q

Interleukins

A

Stimulate bone resorption

21
Q

IL-1

A

Most potent bone resorption stimulator

22
Q

What decreases IL-1 expression?

A

Estrogen

23
Q

What stimulates PTH production

A

Falling blood Ca levels

24
Q

Wolff’s Law

A

Bone reacts to mechanical cyclic stress by changing internal and external architecture to better withstand stress over a period of time

25
Q

Three reasons bones undergo constant remodeling

A
  1. Repair microdamage
  2. Maintain strength
  3. Regulate serum Ca
26
Q

Three steps in bone remodeling process

A
  1. Microdamage -> RANKL release
  2. Osteoclast activation -> bone resorption
  3. Reversal to bone formation, mineralization, and osteocytogenesis
27
Q

Primary vs secondary (direct vs indirect) fracture healing

A

Primary: requires no movement between fractured fragments
Secondary: some movement between fragments present

28
Q

Does a callus form in primary fracture healing?

A

No

29
Q

Three possibilities for fracture healing based on amount of space between fragments

A

No space: lamellar bone forms
200-500nm space: woven bone -> lamellar bone
500+nm space: indirect healing occurs

30
Q

Five stages of indirect fracture healing

A
  1. Hematoma
  2. Week 1: Inflammatory phase
  3. 2-3 weeks: soft callus forms
  4. 4-12 weeks: hard callus forms
  5. For years: remodeling of bone
31
Q

Three anti-resorption therapeutic agents

A

Bisphosphonates, estrogen, denosumab

32
Q

Bisphosphonates

A

Inhibit osteoclast activity

33
Q

Denosumab

A

mAb against RANKL

34
Q

PTH: continual vs intermittent (daily) administration (therapeutically)

A

Continual: stimulates osteoclast formation
Intermittent: stimulates bone formation

35
Q

Estrogen

A

Decreases RANKL production -> fracture healing

36
Q

Thyroid hormones

A

Stimulate osteoclasts

37
Q

Glucocorticoids

A

Inhibit Ca absorption in gut -> increased PTH -> increased osteoclasts

38
Q

GH

A

Stimulates osteoblasts -> increase callus formation and fracture strength