5.3 lect - cartilage, bone, synovial joint Flashcards

1
Q

which is the “apical” side of an osteoblast?

A

faces the osteoid

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2
Q

the apical side of this bone cell is thrown into folds to increase surface area

A

osteoblast (secreting osteoid)

osteoclast has ruffle border (H+ pumps)

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3
Q

what are the 3 specialized regions of an osteoclast?

A
  • ruffle border (incrased surface area for H+ pumps into howship lacuna)
  • sealed clear zone (actin filaments & adhesion proteins seal off active resorbing area)
  • basolateral region (exocytosis of digested vesicles to enter capillaries and systemic circulation)
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4
Q

what is hyaline cartilage

A

a hydrated matrix of type II collagen with entrapped chondrocytes

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5
Q

while chondrocytes are found at the center of a hyaline cartilage tissue, these cells are found on the periphery

A

chondroblasts

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6
Q

chondrocytes that divide after being entrapped form …

A

isogenous groups

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7
Q

the cartilage matrix can be divided by staining properties into __ and __

A
  • territorial matrix (rich in GAGs) near chondrocytes

- interterritorial matrix away from chondrocytes

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8
Q

the dense connective tissue layer surrounding hyaline cartilage is called

A

perichondrium

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9
Q

this tissue type is usually found where dense connective tissue inserts into cartilage

A

fibrocartilage

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10
Q

what is contained within canaliculi?

A

processes of osteocytes

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11
Q

this cell functions to secrete osteoid, pre-mineralized bone matrix

A

osteoblasts

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12
Q

a quiescent osteoblast is a…

A

bone lining cell

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13
Q

5 resident cells of bone

A
osteoprogenitor
osteoblast
bone lining
osteocyte
osteoclast
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14
Q

this cell is responsible for resorption of bone

A

osteoclast

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15
Q

how is an inactive osteoclast morphologically different from an active osteoclast?

A

inactive - mononucleated (monocyte)

active - large multinucleated (fusion of monocytes)

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16
Q

how does an osteoclast resorb bone?

A

creates a sealed space, howship’s lacuna, into which H+ ions and enzymes are pumped across the ruffled border

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17
Q

creates a sealed space, howship’s lacuna, into which H+ ions and enzymes are pumped across the ruffled border

A

osteoclast

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18
Q

together, __, __, and __ surround the surfaces of mineralized bone

A

osteoblasts
osteoclasts
bone lining cells
(perhaps morphologically indistinguishable osteoprogenitor cells)

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19
Q

T/F osteoprogenitor cells give rise to osteoclasts

A

false

monocytes do

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20
Q

osteoprogenitor cells give rise to…

A

osteoblasts
osteocytes
bone lining cells

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21
Q

__ bone comes about through remodeling

A

lamellar (secondary) bone

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22
Q

__ bone is newly formed

A

woven (primary) bone

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23
Q

how is a haversian canal formed?

A

-cutting cone of osteoclasts
-closing cone of osteoblasts
(tunneling along axis of maximal stress)

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24
Q

cutting cone

A

cone of osteoclasts tunneling along axis of maximal stress to make room for a new osteon

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25
Q

closing cone

A

cone of osteoblasts filling tunnel created by cutting cone of osteoclasts along axis of maximal stress to make new osteon

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26
Q

what ensures patency of the bone’s blood supply?

A

volkmann’s canals growing across lamellae to join haversian canals

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27
Q

what is an “anastomosing network”

A

linking of streams

e.g. volkmann’s canals connect haversian canals to creat an anastomosing network of vessels

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28
Q

T/F bone is a static structure

A

false

dynamic structure, constantly remodeling

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29
Q

where is cartilage present on ribs?

A

ventrally at connections to sternum

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30
Q

this tissue functions in:

  • structure with flexibility
  • structure in the context of intermittent forces (joints, respiratory system)
  • shock absorption
  • fast growth
A

cartilage

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31
Q

this tissue functions in:

  • withstanding compressive and tensile forces
  • levers for movement
  • protection of organs
  • calcium storage
A

bone

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32
Q

cells dispersed in an ECM =

A

connective tissue

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33
Q

cells of this connective tissue are not especially important to funciton

A

cartilage

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34
Q

“hylos” =

A

greek for glassy

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35
Q

hyaline cartilage matrix is composed of…

A
70% water
collagen
ground substance
glycoproteins (e.g. fibronectin)
proteoglycans
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36
Q

what is the predominant material in cartilage?

A

water

70%

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37
Q

why are there large vacuoles in cartilage on LM?

A

fixation artifact

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38
Q

T/F cartilage is avascular

A

true

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39
Q

this ECM component has a “bottle brush” appearance

A

proteoglycan aggregates

-glycoscylations stemming / radiating out from hyaluronic acid core

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40
Q

what is a proteoglycan in the ECM?

A

glycoscylations stemming / radiating out from hyaluronic acid core

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41
Q

aggrecan

A

one type of proteoglycan aggregate

-glycoscylations stemming / radiating out from hyaluronic acid core

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42
Q

glycoscylations stemming / radiating out from hyaluronic acid core

A

proteoglycan aggregate

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43
Q

proteoglycans bind…

A

water and collagen

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44
Q

proteoglycans have a net __ charge

A

negative

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45
Q

how are nutrients transported to chondrocytes?

A

via hydrated ECM of proteoglycan aggregates and water

through compressive forces

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46
Q

is territorial matrix more eosinophilic or more basophilic? why?

A
basophilic
more GAGs (which are negative)
47
Q

surrounds isogenous groups in hyalin cartilage

A

territorial matrix

48
Q

between isogenous groups in hyalin cartilage

A

interterritorial matrix

49
Q

what kind of cartilage is found in the trachea and lung airways?

A

hyaline cartilage

50
Q

eustation tube
epiglottis
external ear
are made up of…

A

elastic cartilage

51
Q

the epiglottis is made of…

A

elastic cartilage

52
Q

cartilage with thin dark staining fibers in the matrix is probably…

A

elastic cartilage

53
Q

what kind of cartilage in intervertebral disks?

A

fibrocatilage

surrounding juicy nucleus pulposus

54
Q

herniated disk

A

fibrocartilage in intervertebral disk tears and juicy nucleus pulposus leaks out

55
Q

how to distinguish chondrocytes from fibroblasts in fibrocartilage?

A

round cells - chondrocytes

fusiform cells - fibroblasts

56
Q

synovial fluid consists of…

A

water (transudate from capillary plexus)
proteoglycans
hyaluronic acid
(secreted by B-cell synoviocytes)

57
Q

2 layers of synovial membrane

A
  • intimal layer (1-4 layers of synoviocytes)
  • subintimal layer (fibrovascular)
  • both encompassed within joint capsule*
58
Q

intimal layer of synovial membrane

A

1-4 layers of synoviocytes
A-cells (macrophages)
B-cells (synovial fluid secretion)

59
Q

T/F synovial fluid consists of a mixture of transudate from capillary plexus and ground substance

A

true

60
Q

subintimal layer of synovial membrane

A

fibrovascular layer between intima and joint capsule

61
Q

T/F cartilage has a highly limited capacity for repair

A

true

avascular

62
Q

T/F cells in the perichondrium have the capacity to differentiate into chondrocytes to aid cartilage repair

A

true

but this capacity is limited

63
Q

cartilage repair

A
  • cells in perichondrium have limited capacity to differentiate into chondrocytes
  • defects are often filled by fibroblasts, which produce dense scar limiting and impairing recovery of function
64
Q

T/F any trauma to cartilage (over-training, surgery, etc) does not repair well and will probably scar

A

true

65
Q

fibronectin

A

a glycoprotein found in round substances of connective tissues

66
Q

what substance is exclusively found in cartilage?

  • type I collagen
  • fibronectin
  • type II collagen
  • heparin
A

type II collagen

67
Q

what are the consequences of the avascular an non-innervated nature of catilage

A
  • lower chance of transplant rejection
  • poor recovery after damage
  • no direct pain from damage
  • diffusion from surrounding ct must supply metabolic support
68
Q

T/F cartilage has a relatively lower chance of transplant rejection

A

true

avascular and non-innervated

69
Q

T/F no direct pain is felt from cartilage damage

A

true

avascular and non-innervated

70
Q

T/F diffusion from surrounding connective tissue supplies metabolic support to chonrocytes

A

true

avascular and non-innervated

71
Q

where does bone marrow exist?

A

between trabeculae of spongy cancellous trabecular bone

72
Q

this type of bone is highly organized to confer strength without increasing weight (e.g. like the eiffel tower)

A

trabecular spongy cancellous bone

73
Q

this type of bone is a three-dimensional latticework that uses arches, rods, and plates to counter forces and provide maximum support for weight

A

trabecular spongy cancellous bone

74
Q

3 main parts of compact bone

A

outer circumferential lamellae
inner circumferential lamellae
osteons (haversian systems)

75
Q

T/F circumferential lamellae refer to osteons

A

false

surround entire inside or outside of bone

76
Q

T/F osteons usually run perpendicular to the long axis of the bone

A

false

usually run parallel to long axis of bone

77
Q

how are adjacent lamella of an osteon oriented to one another?

A

90 degree angles (opposite twisting slants)

-reason for appearance in polarizing microscope

78
Q

what are the lamellae of the osteon?

A

10% water
45% organic material (mostly type I collagen, some ground components)
45% mineral (hydroxyapatite crystals Ca10(PO4)6(OH)2 )

79
Q

what is the organic material of bone?

A

mostly type I collagen
some ground components
-osteonectin (binds mineral to collagen I)
-osteopontin (binds cells to matrix)

80
Q

what is the ground substance in bone?

A
  • osteonectin (binds mineral to collagen I)

- osteopontin (binds cells to matrix)

81
Q

what is bone mineral?

A

hydroxyapatite crystals

Ca10(PO4)6(OH)2

82
Q

what is hydroxyapatite?

A

Ca10(PO4)6(OH)2

bone mineral

83
Q

what is the collagen type in bone?

A

type I

84
Q

how is bone mineralized?

A

hydroxyapetite is deposited inside type I collagen fibers, between fibrils

85
Q

osteogenesis imperfecta

A

bone deprived of type I collagen elements, minerals are more brittle, bones broken more easily

86
Q

T/F osteoblasts are interconnected by gap junctions

A

true

87
Q

on EM, a cell with prominent golgi apparati beside a layer of collagen beside a layer of very dark black probably depicts…

A

an osteoblast next to an osteoid layer next to a mineralized bone matrix

88
Q

T/F canaliculi are the osteocyte processes that communicate with one another in tiny canals across osteon lamellae

A

false

canaliculi are the actual tunnels, not the osteocyte processes within them

89
Q

how are osteocyte processes linked to one another?

A

gap junctions

90
Q

what is one function of an osteocyte?

A

sense forces through the filaments connecting it to bone

91
Q

how do bone lining cells connect to each other?

A

gap junctions

92
Q

T/F gap junctions connect both bone lining cells and osteoblasts to one another

A

true

93
Q

T/F you will be asked to identify osteoprogenitor cells

A

false

too similar morphologically to bone lining cells

94
Q

where are osteoprogenitor cells present?

A

inner cellular periosteum
endosteum
lining haversian canals

95
Q

where do osteoprogenitor cells come from?

A

mesenchymal stem cells

96
Q

osteoclasts regulate …

A

calcium homeostasis

97
Q

how do osteoclasts regulate calcium homeostasis?

A

low serum calcium

  • thryoid secretes parathyroid horomone to inhibit osteoblasts
  • osteoblasts release osteoclast stimulating factor (RANKL) to activate osteoclasts

high serum calcium
-thyroid secretes calcitonin to inhibit osteoclasts

98
Q

how does the thyroid gland regulate calcium homeostasis?

A
  • parathyroid hormone inhibits osteoblasts and stimulates them to release RANKL to activate osteoclasts
  • calcitonin inhibits osteoclasts
99
Q

what gland is key in regulating calcium homeostasis

A

thyroid gland

  • parathyroid hormone inhibits osteoblasts and stimulates them to release RANKL to activate osteoclasts
  • calcitonin inhibits osteoclasts
100
Q

how does parathyroid hormone affect bone?

A

inhibits osteoclasts and stimulates them to release RANKL to activate osteoclasts

  • increase serum calcium concentrations
  • released by parathyroid gland
101
Q

how does calcitonin affect bone?

A

inhibits osteoclasts

  • decreases serum calcium levels
  • released by thyroid gland
102
Q

RANKL

A

osteoclast stimulating factor

-released by osteoblasts in response to parathyroid parathyroid hormone

103
Q

what is the process by which the transition from woven immature bone to lamellar mature bone accomplished?

A

bone remodeling

104
Q

bone remodeling

A

what is the process by which the transition from woven immature bone to lamellar mature bone accomplished

105
Q

describe bone remodeling in 3 steps

A
  • cutting cone of osteoclasts
  • vascularization
  • closing cone of osteoblasts
106
Q

what happens to osteoblasts in the closing cone during bone remodeling?

A

become trapped osteocytes or bone lining cells along haversian canal

107
Q

what is the name of the structure created by a cutting cone of osteoclasts

A

resorption tunnel

108
Q

T/F bone remodeling ceases when all woven immature bone has been converted to lamellar mature bone

A

false

remodeling continues to respond to stressors, creating new osteons and revising structure

109
Q

type X collagen

A

short chain collagen expressed by hypertrophic chondrocytes during endochondral ossification at the growth plate

110
Q

short chain connective tissue fibers expressed by hypertrophic chondrocytes during endochondral ossification at the growth plate

A

type X collagen

111
Q

how can you differentiate between an osteoblast and an osteoclast on EM?

A
  • osteoblast: folds are not as apparent, collagen fibers in osteoid unmineralized matrix
  • osteoclast: ruffled border is Very apparent, no apparent collagen fibers in demineralized matrix
112
Q

T/F gogli aparati are apparent in EM of osteoblast but not of osteoclast

A

false

  • osteoblast secretes osteoid and vesicles for calcification
  • osteoclast repackages endocytosed vesicles for basolateral release for eventual reuptake into plasma
113
Q

how to tell difference between osteoblast and osteocyte on EM?

A

-osteocyte will be completely surrounded by mineralized matrix, osteoblast will only have apical mineralized matrix
(both may have a layer of unmineralized matrix - apically for osteoblast, in lacuna for osteocyte)