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MSK Final > Physiology of Bone > Flashcards

Physiology of Bone Flashcards

1
Q

What is mainly found in the organic portion of the ECM in bone?

A

collagen

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2
Q

What organic component in the ECM of bone aids in hydroxyl apatite crystallization and binds calcium?

A

Osteonectin and osteocalcin

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3
Q

What organic components of the ECM of bone binds growth factors?

A

Proteoglycans

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4
Q

What organic components of the ECM in bone mediate osteoclast adhesion to bone surface (bind osteoclast integrins)

A

Sialoproteins, osteopontins, and thrombospondin

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5
Q

What are the main inorganic components of the ECM of bone?

A

inorganic hydroxyapatites or mineral salts, primarily calcium phosphate

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6
Q

What functions to pack tightly, contributing to the hardness and ability to resist compression?

A

the inorganic components

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7
Q

What is the function of osteogenic cells?

A

develop into osteoblasts

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8
Q

Where are osteogenic cells located?

A

in the deep layers of the periosteum and the marrow

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9
Q

What is the function of osteoblasts?

A

Bone formation

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10
Q

Where are osteoblasts found?

A

in growing portions of bone, including periosteum and endosteum

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11
Q

what is the function of osteocytes

A

maintain mineral concentration of matrix

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12
Q

where are osteocytes found?

A

entrapped in matrix

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13
Q

what is the function of osteoclasts?

A

bone resorption

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14
Q

where are osteoclasts found?

A

bone surfaces and site of old or injured bone matrix

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15
Q

Which bone cell type is cuboidal shaped?

A

osteoblast

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16
Q

which bone cell type directly regulates bone matrix synthesis and mineralization?

A

osteoblasts

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17
Q

How doe osteoblasts indirectly control bone resorption?

A

Through release of paracrine factors that regulate osteoclasts (RANKL/OPG)

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18
Q

What do osteoblasts eventually become?

A

osteocytes

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19
Q

Which bone cell can initiate apoptosis?

A

Osteoblasts

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20
Q

Which bone cell type is the terminally differentiated osteoblast?

A

Osteocytes

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21
Q

Where do osteocytes become trapped?

A

Within the newly deposited bone matrix

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22
Q

How do osteocytes respond to mechanical loading?

A

by releasing paracrine factors

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23
Q

Which bone cell secretes acid and lytic enzymes?

A

Osteoclasts

24
Q

Which bone cells are multinucleated and are derived from mononuclear cells in the bone marrow?

A

Osteoclasts

25
Q

What stimulates the proliferation and differentiation of osteoblasts and bone formation?

A

TGF-B

26
Q

What increases OPG production?

A

TGF-B

27
Q

What is a potent inducer of osteoblasts and bone formation?

A

Bone Morphogenic Proteins (BMPs)

28
Q

How is BMP used clinically?

A

rhBMP-2 is used in fracture healing and spinal fusions

29
Q

What is secreted by osteoblasts, binds RANKL, and prevents osteoclast activation?

A

Osteoprotegerin (OPG)

30
Q

What increases proliferation of osteoblasts and enhances callus formation during fracture repair?

A

Fibroblast Growth Factors (FGFs)

31
Q

What does FGF-2 stimulate?

A

Angiogenesis during fracture repair

32
Q

What is stimulated by growth hormone and increases bone collagen matrix synthesis and inhibits degradation?

A

Insulin-like growth factors (IGFs)

33
Q

What increases collagen synthesis?

A

Platelet Derived growth factor (PDGF)

34
Q

What activates osteoclasts for bone resorption?

A

RANKL

35
Q

What secretes RANKL?

A

osteoblasts

36
Q

What is RANKL regulated by?

A

OPG

37
Q

What stimulates bone resorption and which is the most potent?

A

Interleukins; IL-1 is the most potent

38
Q

What is IL-1 expression decreased by?

A

Estrogen

39
Q

What signals release of PTH?

A

Falling blood calcium levels (hypocalcemia)

40
Q

What does PTH signal?

A

Signals osteoclasts to degrade bone matrix and release Ca into the blood

41
Q

Limited movement would result in which type of fracture healing?

A

indirect bone healing

42
Q

No movement would result in which type of fracture healing?

A

direct bone healing

43
Q

When is the inflammatory phase of indirect (secondary) fracture healing?

A

~1 week

44
Q

When is the soft callus formation in indirect (secondary) fracture healing?

A

weeks 2-3

45
Q

When is the hard callus formation in indirect (secondary) fracture healing?

A

weeks 4-12

46
Q

When does remodeling of bone occur in indirect (secondary) fracture healing?

A

years

47
Q

If there is direct contact between fragment ends, what forms?

A

lamellar bone

48
Q

If there is a gap of 200-500 nm, what forms?

A

woven bone and then eventually lamellar bone

49
Q

If there is a gap of 500 nm what occurs?

A

Indirect healing

50
Q

What inhibits osteoclast activity and induces osteoclast apoptosis?

A

bisphosphonates

51
Q

What is a monoclonal antibody against RANKL?

A

Denosumab

52
Q

What induces osteoblast proliferation and activity for increased bone matrix production?

A

BMP-2

53
Q

What effect do thyroid hormones have on bone metabolism?

A

They (thyroxine and triiodothyronine) stimulate osteoclastic bone resorption

54
Q

What effect do glucocorticoids have on bone metabolism?

A

they inhibit calcium absorption from gut, which causes increased PTH and therefore increased orthoclastic bone resorption

55
Q

What does intermittent exposure to PTH stimulate?

A

osteoblasts and increased bone formation

56
Q

What does more chronic exposure of pathological levels of PTH stimulate?

A

osteoclasts to release calcium, which can lean to hypercalcemia

57
Q

What effect does growth hormone have on bone metabolism?

A

It increases callus formation and fracture strength by stimulating osteoblasts

MSK Final (16 decks)

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