17. Cell biology of bone Flashcards Preview

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Flashcards in 17. Cell biology of bone Deck (21)
1

Osteoblasts action ich

build bone by secereting collafen and catalyzing mineralization

2

bone mineralization is process in which

crystals of calcium phosphate are produced and laid down within the bone's fibrous matrix

3

Osteoblasts - differentiate from

mesenchymal stem cells

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Osteoblasts - differentiate from ( where )

mesenchymal stem cells in periosteum

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osteoclasts apperance

multinucleated cells

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osteoclasts action

dissolce bone by secreting acid and collagenases

7

osteoclas - differentiate from

monocytes
macrophages

8

parathyroid hormone action on bone

- low intermittent levels --> anabolic effects ( bulilding bone ) on osteoblasts and osteoclasts ( indirect)
-chronically increased PTH ( 1ry hyperparath) --> catabolic effect ( osteitis fibrosa cystica)

9

estrogen action on bone

1. inhibits apoptosis in osteoblasts
2. induce apoptosis in osteoclasts

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bone - estrogen deficiency -->

excess cycles of remodelling --> bone resorption leads to osteoporosis

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bone - multinucleated cells

osteoclasts

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bone - monocytes and macrophages are differentiate to

osteoclasts

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bone - mesenchymal stem cells are differentiate to

osteoblasts

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• What is the source of osteoblasts, and how do they build bone?

Mesenchymal stem cells in the periosteum differentiate into osteoblasts, which secrete collagen and catalyze mineralization

15

• What secretions of osteoclasts effectively dissolve bone?

Acids and collagenases

16

• A doctor gives his rival a drug so that he can no longer break down old bone cells. Which enzyme does this drug most likely inhibit?

Collagenase, as osteoclasts release acids and collagenases to dissolve old bone

17

• The cells that dissolve bone are derived from what precursor cells?

Osteoclasts are derived from monocytes and macrophages

18

• How is parathyroid hormone involved in normal bone physiology?

At low, intermittent levels, it exerts anabolic (bone-building) effects by activating osteoblasts directly and osteoclasts indirectly

19

• A patient has osteitis fibrosa cystica. Which hormone is likely chronically elevated in him?

PTH, leading to excess bone catabolism

20

• How does estrogen exert its effects on bone?

It inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts

21

• How does estrogen deficiency lead to osteoporosis?

Excess remodeling cycles and bone resorption occur without the protective effects of estrogen, leading to osteoporosis

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