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Histology block 2 > bone > Flashcards

bone Flashcards

1
Q

describe the vascularity of bone

A

well-vascularized

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2
Q

what composes the inorganic portion of bone?

A

hydroxyapatite crystals

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3
Q

what composes the organic portion of bone?

A

collagen type I and ground substance

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4
Q

what are the 2 layers of periosteum?

A

outer- fibrous, dense CT

inner- cellular, osteoprogenitor cells

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5
Q

what is endosteum?

A

connective tissue covering the internal surfaces of bone, like aversion canals

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6
Q

describe osteopblasts

A

immature bone cells that develop from osteoprogenitor cells

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7
Q

what do osteoblasts secrete?

A

osteoid- organic portion of bone only (not mineralized)

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8
Q

where are osteoblasts located?

A

underlying the periosteum

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9
Q

what is the appearance of osteoblasts?

A

cuboidal or columnar, basophilic cytoplasm

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10
Q

what are osteocytes?

A

mature bone cells

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11
Q

where do osteocytes reside?

A

in lacunae

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12
Q

who do adjacent osteocytes communicate?

A

via cytoplasmic processes that are housed in canaliculi

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13
Q

what connects the cytoplasmic processes of osteocytes?

A

gap junctions

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14
Q

what are osteoclasts?

A

bone resorbers

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15
Q

what are the progenitor cells of osteoclasts?

A

share progenitor cells with monocytes, part of the mononuclear phagocyte system

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16
Q

where do osteoclasts reside?

A

Howship’s Lacunae

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17
Q

what is the basic appearance of an osteoclast?

A

large, multi-nucleated cell with a ruffled border

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18
Q

what is the “clear zone” in osteoclasts?

A

zone around the ruffled border that is clear of organelles but abundant in actin microfilaments that allow osteoclasts to attach to bone

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19
Q

how do osteoclasts break down bone?

A

through the secretion of lysosomal enzymes

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20
Q

what are the 2 features of spongy bone?

A

spicules- spikes, trabecula- bridges

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21
Q

describe primary bone

A

immature, irregular/unorganized collagen fibers, low mineral content, abundant osteocytes

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22
Q

where is primary bone found in an adult? (3)

A

tooth sockets, near skull sutures, tendon insertions

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23
Q

what are other names for primary bone?

A

immature or woven bone

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24
Q

describe secondary bone

A

mature, more typical in adults, well-organized collagen fibers, contain haversian systems/lamellae

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25
Q

what are other names for secondary bone?

A

mature or lamellar bone

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26
Q

described haversian systems

A

concentric lamellae of collagen fibers and bone matrix, center of system in an endosteum lined canal

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27
Q

what is housed in Haversian Canals?

A

blood vessels, nerves and loose CT

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28
Q

what is the orientation of Haversian Canals?

A

longitudinal

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29
Q

in what type of bone are Haversian systems most commonly seen?

A

compact bone

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30
Q

what are Volkmann’s Canals?

A

perpendicular canals that provide route for communication between Haversian Systems and communication with bone marrow

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31
Q

what is the primary route for newly formed blood cells to exit bone marrow cavity?

A

volkmann’s canals

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32
Q

describe the 3 types of lamellae

A

outer circumferential- directly under periosteum
inner circumferential- adjacent to marrow cavity
interstitial- remnants of Haversian systems that have degenerated during bone remodeling

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33
Q

what are the 3 general structural components of long bones?

A

diaphysis, epiphysis and metaphysis

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34
Q

which part comprises the shaft?

A

diaphysis

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35
Q

what is the composition of the diaphysis?

A

outer-compact bone

inner- spongy bone

36
Q

what comprises the end of long bones?

A

epiphysis

37
Q

what type of bone is the epiphysis?

A

outer- thin compact layer

inner- spongy bone

38
Q

what is another name for metaphysis?

A

growth plate

39
Q

what are the 2 important structural factors of the metaphysis?

A

highly vascularized and innervated

40
Q

what is an example of a long bone?

A

humerus, femur, etc

41
Q

what is an example of short bone?

A

metacarpals

42
Q

what are the structural characteristics of short bone?

A

outer- compact bone

inner- spongy bone

43
Q

where are flat bones found?

A

skull

44
Q

what is the general structure of flat bones?

A

outer-compact bone (plates)

inner- spongy bone (dipole)

45
Q

what type of bone undergoes intramembranous ossification?

A

flat bones

46
Q

why is is called “intramembranous ossification”?

A

because mesenchymal cells condense to form a membrane

47
Q

what do mesenchymal cells differentiate into in intramembranous ossification?

A

osteoblasts, to form primary ossification center

48
Q

what is the method for most long and short bone formation?

A

endochondral ossification

49
Q

what forms the scaffolding in endochondral ossification?

A

hyaline cartilage

50
Q

where is the primary ossification center in long bones?

A

diaphysis

51
Q

what happens to the perichondrium in endochondral ossification?

A

perichondrium becomes highly vascularized allowing for differentiation of chondrogenic cells to osteoprogenitor cells to osteoblasts

52
Q

what happens to the perichondrium once osteoblasts are present?

A

it is renamed to periosteum

53
Q

what is the bone collar?

A

structure at primary ossification center that is formed by osteoblasts. located just deep to periosteum

54
Q

through what process does the bone collar form?

A

through intramembranous ossification

55
Q

what are one marrow spaces formed from?

A

chondrocytes that hypertrophy and degenerate, the coalescence of their lacuna form marrow spaces

56
Q

where are the blood vessels found in forming bone?

A

osteogenic bud

57
Q

how does forming bone access the osteogenic bud?

A

osteoclasts eat away the bone collar

58
Q

in what direction does the diaphysis grow?

A

toward the epiphysis

59
Q

where is the secondary ossification center?

A

epiphysis

60
Q

what is another name for secondary ossification?

A

closure of growth plate

61
Q

does secondary ossification center have a bone collar?

A

NO

62
Q

after growth plates close, what 2 places retained their cartilage?

A

articular surfaces and epiphyseal plate

63
Q

name the 5 zones of the epiphyseal plate

A 
Resting Cartilage
Proliferation
Hypertrophy
Calcification
Ossification
64
Q

what is occurring at the zone of resting cartilage?

A

nothing! contains resting hyaline cartilage

65
Q

what is occurring at the zone of proliferation?

A

chrondrocytes proliferate, sometimes with “coin stack” appearance

66
Q

what is occurring at the zone of hypertrophy?

A

chrondrocytes enlarge before they die and lose their ability to maintain normal cellular functioning

67
Q

what is occurring at the zone of calcification?

A

chondrocytes degenerate and the cartilage matrix that surrounded the chondrocytes begin to calcify, often appears basophilic

68
Q

what is occurring at the zone of ossification?

A

osteoblasts present, depositing bone matrix on the cartilage scaffold, acidophilic

69
Q

when are osteoblasts renamed osteocytes?

A

when they are entirely surrounded by matrix (housed in lacunae)

70
Q

how does bone grow in width?

A

appositional growth

71
Q

describe the 6 steps of fracture repair

A 
blood clot forms 
periosteum and endosteum proliferate
hyaline cartilage forms 
primary bone is laid down 
bone callus unites fracture
remodeling occurs
72
Q

what is the purpose of PTH?

A

raise blood calcium

73
Q

how does PTH raise blood calcium?

A

activates osteoprogenitor cells to make more cells, more osteoclasts are formed and bone resorption occurs (indirect mechanism)

74
Q

what is the purpose of calcitonin?

A

lower blood calcium

75
Q

how does calcitonin lower blood calcium?

A

stabilizes bone by inhibiting osteoclasts (direct)

76
Q

what is the role of estrogen in bone?

A

estrogen limits excessive bone resorption

77
Q

how does estrogen limit bone resorption?

A

inhibition of osteoclasts, regulation of osteoblasts

78
Q

how does menopause affect bone density?

A

estrogen levels decrease in menopause, allows increased bone resorption

79
Q

what is the effect of estrogen on OPG?

A

estrogen upregulates OPG

80
Q

what is the effect of estrogen on OPGL?

A

estrogen down regulated OPGL

81
Q

describe osteopetrosis

A

defective bone resorption, osteoclasts lack ruffled borders

82
Q

describe osteitis fibrosa cystica

A

abnormally high osteoclast activity

83
Q

describe osteomalacia

A

impaired mineralization leading to weak bones, can be 2/2 calcium deficiency

84
Q

what type os cancer frequently met to bone?

A

prostate, breast and lung

85
Q

what is a benign bone tumor?

A

osteoblastoma

86
Q

what is a malignant bone tumor?

A

osteosarcoma

87
Q

what are he histologic characteristics of woven bone?

A

few osteons, larger osteocytes, irregular collagen bundles

Histology block 2 (9 decks)

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