Bone: Structure and Function Flashcards

1
Q

_______ is the major connective tissue of the body

A

bone

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2
Q

the extreme hardness of bone is due to ________

A

mineralization of its extracellular matrix

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3
Q

5 functions of bone

A
  • provide support for the body’s organs and soft tissue
  • function as attachment sites for muscles
  • provide protection for organs
  • enclose hematopoietic tissues
  • serve as metabolic stores for selected minerals
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4
Q

______: very dense bone

A

compact or cortical bone

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5
Q

______: lattice-like bone, composed of spicules and trabeculae of bone within bone marrow

A

cancellous/trabecular/spongy bone

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6
Q

5 features of (the majority of) bones

A
  • articular surfaces covered by articular cartilage
  • cortex
  • a medullary cavity
  • periosteum
  • endosteum
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7
Q

______: the outer wall of compact bone

A

cortex

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8
Q

_______: the space bounded by the cortex that contains cancellous bone and bone marrow

A

medullary cavity

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9
Q

_____: a layer of fibrous connective tissue tat completely lines the external surface of the cortex except for the articular surfaces

A

periosteum

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10
Q

_____: a layer of fibrous connective tissue that completely lines the inner surface of the cortex as well as the surfaces of spicules/trabeculae of cancellous bone and the canals of cortical bone

A

endosteum

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11
Q

3 additional features of long bones

A
  • diaphysis
  • metaphysis
  • epiphysis
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12
Q

flat bones of the skull develop by ________ ossification

A

intramembranous ossification

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13
Q

most bones develop via _____ ossificatin

A

endochondral ossification

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14
Q

what makes up the axial skeleton?

A

the head, ribs, vertebrae, and sternum

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15
Q

what makes up the appendicular skeleton?

A

thoracic and pelvic limbs

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16
Q

3 examples of flat bones

A
  • skull
  • scapula
  • pelvis
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17
Q

long bones make up the _____

A

appendicular skeleton

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18
Q

the primary center of ossification occurs in the _____

A

diaphysis

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19
Q

the secondary center of ossification occurs in the _____

A

epiphysis

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20
Q

_____: the end of a long bone

A

epiphysis

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21
Q

_____: the shaft or central part of a long bone

A

diaphysis

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22
Q

_____: the wide portion of a long bone that contains the growth plate (funnel shaped)

A

metaphysis

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23
Q

the ______ layer of the periosteum participates in appositional growth

A

osteogenic (cambium) layer

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24
Q

4 types of cells unique to bone

A
  • osteoblasts
  • osteocytes
  • bone lining cells
  • osteoclasts
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25
Q

osteoblasts are cellularly derived from _______

A

mesenchymal stem cells

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26
Q

osteoblasts are present where on the bone?

A

on the bone surfaces

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27
Q

_____ are responsible for bone formation

A

osteoblasts

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28
Q

osteoblasts are responsible for _____

A

bone formation

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29
Q

osteoblasts produce ______ and initiate ______

A
  • bone matrix (osteoid)

- mineralization of the bone matrix

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30
Q

What is a counterintuitive function performed by osteoblasts?

A

they control the resorption of matrix by the osteoclasts

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31
Q

3 substances/materials produced by osteoblasts

A
  • type I collagen
  • proteoglycans
  • bone specific proteins
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32
Q

(osteoblasts/osteoclasts): possesses a single and eccentric nucleus

A

osteoblasts

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33
Q

(osteoblasts/osteoclasts): ovoid to cylindrical in shape and become more flattened with age

A

osteoblasts

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34
Q

(osteoblasts/osteoclasts): never found singly; occur in groups along bone surfaces

A

osteoblasts

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35
Q

unmineralized bone matrix, known as an _______ is found between active osteoblasts and the bone surface

A

osteoid seam

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36
Q

What is an osteoid seam?

A

the line of unmineralized bone matrix found between active osteoblasts and the bone surface

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37
Q

osteocytes are most abundant where?

A

in mature bone

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38
Q

______: differentiated osteoblasts buried in the bone matrix which subsequently becomes calcified

A

osteocytes

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39
Q

______ occupy the lacunae in mature bone and ______ occupy the canaliculi

A
  • osteocyte nuclei

- osteocyte cell processes

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40
Q

osteocytes sense and translate _____ into _____ to orchestrate bone gain or bone loss as needed

A
  • mechanical strains

- biochemical signals

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41
Q

_______: flattened cells covering resting bone surfaces

A

bone lining cells

42
Q

bone lining cells communicate with osteocytes via ______ within _____

A
  • cell processes

- canaliculi

43
Q

bone lining cells are involved in the regulation of what?

A

the flow of calcium ions from bone to the extracellular fluid

44
Q

certain hormonal and mechanical stimuli induce bone lining cells to convert into __________

A

osteoblasts

45
Q

_______ are involved in the regulation of the flow of calcium ions from bone to the extracellular fluid

A

bone lining cells

46
Q

conversion of bone lining cells into osteoblasts can be triggered by the hormone _____

A

parathyroid hormone (PTH)

47
Q

(osteoblasts/osteoclasts): large and multinucleated cells

A

osteoclasts

48
Q

______ are responsible for bone resorption

A

osteoclasts

49
Q

osteoclasts are responsible for _________

A

bone resorption

50
Q

osteoclasts are cellularly derived from ___________

A

hematopoietic stem cells

51
Q

__________: the resorption surface/concavity of osteoclasts

A
  • resorption bay

- Howship’s lacuna

52
Q

osteoclasts increase activity under the influence of _________

A

parathyroid hormone

53
Q

osteoclasts decrease activity under the influence of _____ and _______

A
  • estrogen

- calcitonin

54
Q

osteocyte activation is controlled by __________ and ________

A
  • osteoblasts

- bone marrow stromal cells

55
Q

bone resorption is regulated mainly via the _________ pathway

A

RANK-RANKL-OPG signaling pathway

56
Q

the RANK-RANKL-OPG signaling pathway is primarily responsible for regulating what process?

A

bone resorption

57
Q

(osteoblasts/osteoclasts) possess numerous vacuoles in the cytoplasm

A

osteoclasts

58
Q

___________: extensive membrane infoldings at the bone/osteoclast interface

A

ruffled borders

59
Q

2 steps to bone resorption

A
  • decalcification of the bone matrix

- digestion of the organic components of the bone matrix (collagen, proteoglycans, etc.)

60
Q

_____________ is the solubilization of calcium salts by acidification of the local microenvironment within the subosteoclastic compartment

A

decalcification of bone matrix

61
Q

digestion of the organic components of bone matrix requires the release of ____________ (______) in the subosteoclastic compartment by exocytosis

A

lysosomal acid hydrolases (cathepsins)

62
Q

three main components of bone matrix

A
  • amorphous ground substance
  • collagen fibers (type I)
  • minerals
63
Q

the 2 primary minerals in bone matrix are _______ and ______ which are arranged into ________ that are deposited in the gap regions of collagen fibers

A
  • calcium
  • phosphorus
  • hydroxyapatite crystals
64
Q

the endosteum is composed of _________ and a ________ lining (osteoprogenitor cells)

A
  • loose connective tissue

- squamous cell lining

65
Q

3 principal lamellar patterns in cortical bone

A
  • haversian systems/osteons
  • interstitial lamellae
  • outer and inner circumferential lamellae
66
Q

_________: consist of concentric rings of matrix surrounding a circular vascular canal

A

haversian systems/osteons

67
Q

__________: angular lamellae situated between haversian systems

A

interstitial lamellae

68
Q

_______: cortical lamellae that extend completely around the entire cortex just beneath the periosteum and endosteum

A

outer and inner circumferential lamellae

69
Q

_______: thin lines of uncalcified matrix that delineate the margins of haversian and interstitial systems are

A

cement (reversal) lines

70
Q

_______: the central openings of haversian systems which contain 1-2 small vessels supported by delicate connective tissue

A

haversian canals

71
Q

most often the vessels found within haversian canals are ______ or ______

A
  • capillaries

- postcapillary venules

72
Q

2 principal vascular channels that communicate with haversian canals and their vessels

A
  • Volkmann’s canals/communicating canals

- perforating canals

73
Q

___________/______: tubes passing transversely or obliquely through the lamellae that connect adjacent haversian canals

A

Volkmann’s canals/communicating canals

74
Q

_________: tubes that allow blood vessels from the periosteum and the endosteum to connect with haversian canals

A

perforating canals

75
Q

the orientation of cancellous bone usually reflects _______________

A

adaptation (modeling) to mechanical stresses applied to the bone

76
Q

trabecular bone is also arranged in lamellae which are oriented ______to the surface

A

parallel

77
Q

sclerostin is secreted by ______

A

osteocytes

78
Q

_______: a protein secreted by osteocytes which binds to the lipoprotein receptor-related protein 5 (LRP5) receptor on osteoblasts, thereby inhibiting bone formation

A

sclerostin

79
Q

What is the function of sclerostin?

A

inhibition of bone formation by binding to the lipoprotein receptor-related protein 5 (LRP5) receptor on osteoblasts (released by osteocytes)

80
Q

at the margins of the ruffled border, the plasma membrane is closely applied to the bone surface, forming the ___________ with an intracellular actin ring that creates an extracellular ______________ in which bone resorption occurs

A
  • sealing zone

- subosteoclastic compartment

81
Q

In order to decalcify bone and solubilize calcium salts, an acidic environment is required. How is this accomplished?

A

The actions of carbonic anhydrase in the cytoplasm of the ruffled border produces bicarbonate and hydrogen ions. The hydrogen ions are then transported into the subosteoclastic compartment by an ATP-dependent proton pump, lowering the pH.

Additionally, chloride ions pass into the subosteoclastic compartment through a cholfide channel, which results in formation of HCl and a highly acidic microenvironment (pH 4.5)

82
Q

the extracellular matrix of bone is approximately one-third ______ and two-thirds _________ inorganic salts

A
  • organic matrix

- inorganic salts

83
Q

the amorphous ground substance of bone includes proteoglycan aggregates composed of ________, ________, and ________

A
  • chondroitin sulfate
  • keratin sulfate
  • hyaluronic acid
84
Q

bone specific proteins of the matrix include ________ and _______, which are synthesized by osteoblasts

A
  • osteocalcin

- osteopontin

85
Q

_______: a bone specific protein bound to hydroxyapatite

A

osteocalcin

86
Q

________: a bone specific cell binding protein like fibronectin that binds to hydroxyapatite

A

osteopontin

87
Q

hydroxyapatite crystals reside principally within _________________

A

the gap regions of collagen fibers

88
Q

(demineralized/organically digested) bones are very resilient and pliable and exhibit considerable tensile strength

A

demineralized

89
Q

(demineralized/organically digested) bones retain their hardness but become extremely brittle

A

organically digested

90
Q

2 mechanisms that appear to influence hydroxyapatite deposition:

A
  • extracellular osteoid and calcifying cartilage contain matrix vesicles are believed to be calcification initiators (since hydroxyapatite crystals appear to form within or near matrix vesicles)
  • collagen fibers and their specific molecular spacing act as nucleation sites for the deposition of hydroxyapatite within the gap regions
91
Q

_________ are believed to be calcification initiators since hydroxyapatite crystals appear to form within or near them

A

matrix vesicles

92
Q

_________ and their specific ___________ act as nucleation sites for the deposition of hydroxyapatite within gap regions

A
  • collagen fibers

- molecular spacing

93
Q

__________: involves the calcification of osteoid within a few days after its formation and accounts for about 70-75% of the total mineralization

A

primary mineralization

94
Q

_________: requires weeks to complete and accounts for 25-30% of the total mineral content

A

secondary mineralization

95
Q

(primary/secondary) mineralization is 70-75% of the total

A

primary mineralization

96
Q

(primary/secondary) mineralization is 25-30% of the total

A

secondary mineralization

97
Q

RANKL has a strong _____ effect on bone resorption

A

stimulatory

98
Q

RANKL is secreted by _________

A

osteoblasts

99
Q

when _____ binds to _______, osteoclast precursor cells differentiate into multinucleated osteoclasts, and mature osteoclasts along bone surfaces are activated

A
  • RANKL

- RANK

100
Q

osteoblasts also secrete _____ (___) which is a decoy receptor with high affinity for RANKL and, as such, acts as an inhibitor of bone resorption

A

osteoprotegerin (OPG)

101
Q

osteoblasts can secrete signals to either stimulate (_______) or inhibit (_______) bone resorption and the balance between these two is a key factor in the regulation of bone resorption and remodeling

A
  • RANKL

- OPG