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Flashcards in LEC 7 - Bone Deck (169):
1

What are the three cell types responsible in the maintaince and construction of bone?

Osteoblasts 

Osteocytes 

Osteoclasts

2

Where do osteoclasts orginate from?

Hematopoietic stem cells

3

What is the function of osteoclasts?

Responsible for bone resorption 

Attach to mineralized bone surface 

4

Where are osteocytes located?

Osteoblasts that have been surrounded bu mineralized osteoid 

Occupying small clear spaces called lacunae 

5

Where do osteoblasts arise from?

Mesenchymal cells 

6

What is the function of osteoblasts?

Initiate mineralization 

Produce matrix

Initiate resorption of the resorption by osteoclasts 

7

What do osteocytes and osteoblasts control together?

Calcium homeostatisis 

8

In what direction does bone grow?

In length by intersitial growth 

Within metaphyseal growth plates 

9

Describe: Endochondral ossification 

Process in which bone desposited at mineralized longitudinal septa of the physes 

10

How many zones are there in the physes?

11

What are the three physeal zones?

Resting 

Proliferative 

Hypertrophic 

12

Describe: Resting Zone

Source cells for proliferative zone 

13

Describe: Proliferative zone

Cell multiply 

Accumulate glycogen 

Produce matrix and become arranged in longitudinal columns 

14

Describe: Hypertrophic zones 

Chondrocytes secrete macromolecules to allow capillary invasion and initiate matrix calcification 

15

What are the two sub-zones of hypertrophic zones?

Maturation 

Degeneration 

Calcification 

16

How does growth of epihysis occur? 

Endochondral ossification at articular-epiphyseal complexes 

(AEC)

17

What is the AEC composed of?

Articular cartilage 

Subajacent temporary growth cartilage 

18

How does bone grow in width?

Intermembranous bone formation 

19

What is the surfaces of bone covered by?

periosteom 

20

What is periosteom made from? 

Loosely attached membrane 

Outer fibrous layer = structural support 

Innter osteogenic layer = normal lamellar apossitional bone 

21

What type of bone is laid down in response to injury?

Abnormal woven bone

22

What hormonal agents are released in response to insult on the bone?

Calcitrol 

PTH 

23

What are two examples of disruption of endochondral ossification?

Growth arrest lines 

Growth retardation lattice 

24

Describe: Growth arrest lines 

Multiple nutrient deficiencies cause the growth plate to become narrow 

Metaphyseal face of the plate can be sealed by layer of bone 

= transverse trabeculation 

25

Describe: Growth retardation lattice

Impairment of osteoclastic resporption of bone within primary trabeculae 

= retention primary trabeculae 

they then elongate because of continous EO 

26

 What does tension cause to the bone?

Resporption 

27

What does compression cause to the bone?

Bone formation

28

Describe: Wolff's Law

Ability of bone to change its shape and size to accomodate altered mechanical use 

29

What happens with normal mechanical use? 

Suppression of resorptive activity = maintaince of bone mass

30

What happens when there is a decrease in mechanical use of a bone?

Bone resorption = less mass 

31

What happens with increased mechanical use of the bone?

Increased bone mass

32

Describe: Woven bone

Newly formed 

Hypercellular bone deposited in reaction to injury 

 

33

When is woven bone normal?

Young animals

34

When is woven bone pathologic?

Adult animals 

35

What does woven bone look like in histiologically?

Collagen fibers randomly arranged 

More numerous osteocytes 

Osteocytes are larger

36

How does injured periosteum resond to injury?

Forms bone 

37

What is reactive periosteal woven bone mostly made of?

Cartilage

38

What decides the production of cartilage from the injured periosteum?

Avalibility of oxygen 

Low = cartilage predominates 

 

39

What can happen to the cartilage once it is from in a low tension oxygen environment?

Endochondral ossification

40

What are the two paths that reactive woven bone can occur?

Remodeled lamellar bone 

-- or -- 

Removed by osteoclastic resorption 

41

Describe: Osteophytes 

New bone that occurs in response to joint injury/instability 

42

What can occur with infectious inflammation of the periosteum?

Marked osteoclastic bone resorption at the periosteal surface

43

What is the problem with the articular cartilage responding to injury?

Minimal capacity of repair due to no blood supply 

44

What happens with erosion of the cartilage?

Clusters of chondrocytes form 

45

What happens if the erosion of the cartilage extends to the subchondral bone?

Mesenchymal cells access teh area and become quickly filled with vascular fibrous CT 

46

What are the causes of sterile injury to the articular cartilage?

Trauma 

Joint instability 

Lubrication failure 

47

What activates MMP's? 

Products of degenerating/reactive chondrocytes 

-- and -- 

Inflammatory cells 

48

What is the function of MMP's?

Digest the matrix

49

What is the mechanism by which the loss of proteoglycans lead to mechanical injury of the cartilage?

Alters hydraulic permeability 

Abnormal joint lubrication 

Increases susceptibility to mechanical injury

50

What does the surface of the articular cartilage look like when there is damage?

Surface is yellow-brown 

Dull, slightly roughended appearance 

51

Term: Fibrillation

Condensed + fray collagen ibers due to loss of proteoglycans

52

Term: Eburnation

Smooth + Shiny surface of subchondral bone after cartilage ulceration

53

How does the synovium respond to injury?

Villous hypertrophy + hyperplasia 

Synoviocyte hypertrophy + hyperplasia 

Pannus formation

54

Describe: Pannus

Fibrovascular + Histocytic tissue 

Arises from synovial membranes 

Spreads over articular cartilage 

55

What is the mechanism by which pannus causes the fusion of joints?

Histocytes + Callagenases from fibroblasts 

lead to lysis and destruction of underlying cartilage 

Fibrous Tissues unite the surfaces = Fibrous ankyloses 

56

Describe: Rickets

Affects bone and epiphyseal cartilage

57

Describe: Osteomalacia 

Effects bones only

58

What is the cause of rickets and osteomalacia?

Vitamin D + Phosphorus deficency 

59

What is rickets and osteomalacia?

Failure of mineralization with subsequent bone deformaties + fractures 

Growing skeleton = Rickets 

Adult Skeleton = Osteomalacia

60

What is the pathogenesis of Rickets and osteomalacia?

Vitamin D deficiency 

Hypercalcemia 

Stimulates secreation of parathyroid hormone 

renal phosphorus loss is enhanced 

Reduce the deposition of calcium further 

61

What lesions are seen with rickets?

Diffuse, irregular thickened growth plates 

Most common at the costo-chondral junctions 

aka Rachitic rosary 

62

What lesions are seen with osteomalacia?

Accumulation of microfractures or fractures

63

What lesions are seen in both rickets and osteomalacia?

Cortical bone can be softened 

Increased depostion of osteoid in trabecular zone

64

Describe: Fibrous osteodystrophy 

Increased, widespread osteoclastic resorption of bone 

Replacement by primitive fibro-osseus tissue 

= weak bones 

65

What can cause primary fibrous osteodystrophy?

Pituitary adenoma 

Carcinoma 

Hyperplasa 

66

What can cause secondary fibrous osteodystrophy?

Hyperparathyroidism 

(nurtritional or renal)

-- and -- 

Pseudohyperparathyroidism 

67

What is the pathogenesis of fibrous osteodystrophy caused by increased PTH?

promotes excretion of phosphorous + retention of calcium

68

What is the pathogenesis of fibrous osteodystrophy when caused by renal disease?

Loss of glomerular function

Inability to excrete P + Inadequate calcitriol production

Hyperphsohatemia 

69

What is the pathogenesis of fibrous osteodystrophy when caused by excess P or inadequate calcium?

Stimulation of osteocytic/osteoclastic bone resorption

Decrease bone mineralization 

Replacement by fibrous CT 

Weak bone structure 

70

What are the disorders of encochondral ossification?

Chondrodysplasias 

Osteochondroses 

71

What are the different types of chondrodysplasias?

Primordial dwarfism 

Spider lamb 

 

72

Describe: Chondrodysplasias

Disorders of bone growth 

Result in primary lesions in growth cartilage 

73

What do chondrodysplasias result in?

Disporportionate dwarfism 

74

What breeds are presdisposed to disportionate dwarfism?

Dachshunds 

Pekingese 

Basset hounds

75

What is the cause of chondrodysplasia resulting in disproportionate dwarfism?

Mutaiton in FGF4 

Inapproriate activation of FGF3 receptor 

Negative regulator of bone growth 

76

Describe: Primordial dwarfism 

Limb length proportional to body length 

 

77

What causes primordial dwarfism?

Endocrine disease or malnutrion 

78

What are examples of dog breeds that have primordial dwarfism?

Miniature schnauzer 

Miniature pinchers 

79

What lambs are at risk for spider lamb chondrodysplasia?

Suffolk 

Hampshire

80

What causes spider lamb chondrodysplasia?

Mutation in FGF3 receptor

Impairs inhibition of chondrocyte proliferation 

Results in elongation of limbs and multiple centers of ossification in the epiphyses

81

What are the three types of osteochondroses?

Latens 

Manifesta 

Dissecans 

82

Describe: Joint mouse

Cartilage or Osteochondral flap that has fractured/detached from articular surface 

83

Describe: Osteochondrosis latens

Well demarcated areas of necrosis of epiphyseal cartilage

Centered on necrotic blood vessels 

84

Describe: Osteochondrosis manifesta

retained necrotic epiphyseal cartilage 

Seen grossly

85

Describe: osteochondrosis dissecans

Lesion at AEC 

Forms cleft in necrotic cartilage with subsequent fracture of articular cartilage 

leads to joing mouse 

86

Term: Osteitis 

Inflammation of bone

87

Term: Periostitis

Inflammation of bone with involvement of medullary cavity 

88

Term: Osteomyelitis 

Inflammation of bone with involvement of medullary cavity 

89

What are the three causes of infectious inflammation of bone?

Hematogenous bacteria 

Fungi 

Virus

90

What is the bacterial form of infectious inflammation of bone most common in?

neonatal foals 

food animals 

91

What are possible bacterial causes of infectious inflammation of the bone?

T. pyogenes 

Strep/Staph 

Salmonella 

E. Coli 

92

What fungi can cause infectious inflammation of the bone?

Coccidioides immitis 

Blastomyces dermatitidis 

93

What can coccidioides + blastomyces do to the bone?

Granulomatous to pyogranulomatous osteomylitis 

94

What viruses are known to cause infectious inflammation in the bone?

Swine fever 

infectious canine hepatitis 

95

What does the viral form of infectious inflammation of the bone cause?

Endothelial damage 

-- and-- 

Ischemic necrosis 

96

What does distemper virus do to the bone?

Infect osteoclast 

Disrupt bone modeling 

Leads to growth retardation

97

What does FeLV do to the bone?

Associated with myelosclerosis 

98

What can cause reactive bone formation?

Fracture repair 

Chronic osteomyelitis 

DJD 

99

Term: Exostosis

Nodular benign bony growth projecting outward from surface of bone

100

Term: Enthesophyte

Calcification of tendon or ligament at the point of its insertions

101

Term: Hyperostosis 

Increased diameter of bone and implies uniform thickening on periosteal surface rather than nodularity

102

Term: Enostosis

Bony growth within medullary cavity 

Originates from cortical-endosteal surface 

= Medullary cavity obliteration 

103

What are the characteristics of hypertrophic osteopathy?

Progressive, bilateral, periosteal new bone formation in diaphyseal regions of distal limbs 

Secondary reaction to primary lesion

104

What are the characteristics of osteochonromas?

Eccentric masses loacted adjacen to physes 

105

What are osteochondromas?

Multiple cartilaginous exostoses 

Reflect a defect in skeletal development 

106

What does osteochondromas look like microscopically?

Outer cap of hyaline cartilage 

Undergo endochondral ossification that give rise to trabecular bone 

107

What are the three types of bone cysts?

Subchondral 

Simple 

Aneurysmal 

108

Describe: Subchrondral cysts 

Sequela to osteochondrosis (failure of EO) 

-- and -- 

DJD (herniation of synovial fluid)

109

Describe: Simple cysts

Contain clear, colorless, seroanguious fluid 

Wall composed of dense fibrous tissue + Woven bone 

 

110

Term: Aneurysmal cyst

Filled with blood 

Not lined by endothelium 

111

What are common bones that are sites of secondary bone neoplasms, in dogs?

Rib shafts 

Vertebral bodies 

Humeral/Femoral metaphyses 

112

In cats where do secondary neoplasms of the bone tend to go?

Appendicular skeleton

113

Where do pulmonary carcinomas tend to go in a cat?

Digits 

114

What predispose an animals to pathologic fractures?

osteoporosis 

osteomyelitis 

bone neoplasia 

115

By what method are fractures of the growth plate classified?

Salter-Harris

116

What does a grade V to VI fracture mean?

Crush growth plate 

117

What does a grade III to IV fracture mean?

Cross growth plate 

118

What does grade I and II fracture mean?

Only involve hypertrophied layers of cartilage 

and/or  

Primary bone trabeculae 

119

What predisposes an animal to fractures of the trabecular bone?

Inflammation 

Necrosis 

120

Term: Infractions

Fractures without external deformation of the cortex

121

Term: Closed fracture

Skin is unbroken

122

Term: Open fracture

skin is broken

bone is exposed to exterior

123

Term: Comminuted 

Bone is shattered in several small pieves

124

Term: Avulsed

Caused by traction of a ligament

125

Term: Greenstick

One cortex of the bone is broken and the other is bent

126

Term: transverse or spiral fracture

Depending on orientation of the fracture line, whatever it looks like

127

Describe: Stable fracture repair

Immobilization of fractured ends to give relative stability 

but NOT surgically fixed 

128

What is the first step in stable fracture repair?

Macrophages + Platelets in: 

Blood clot 

Proliferating osteogenic tissue 

Produce growth factors which stimulate proliferation of repir tissue  

aka woven bone 

129

What are the growth factors secreted by the macrophages + platelets in the first stage of stable fracture repair?

Bone Morphogenic proteins 

TGF-B

PDGF

130

What forms granulation tissue in stable fracture repair?

Undifferenitiated mesenchymal cells penetrate area

131

Where do the undifferentiated mesenchymal cells come from in stable fracture repair?

Periosteum 

Endosteum 

Medullary cavity 

132

What is the outcome of the granulation tissue in stable fracture repair?

Cartilage 

-- and -- 

Bone metaplasia

133

What are the final stages of stable fracture repair?

Primary callus formation (woven bone) 

Secondary callus formation forms when woven bone is replaced by lamellar bone

134

Describe: Rigid fracture repair

Surgical intervention that involves the application of devices to keep the bone ends in contact with each other for fracture stability during the repair process 

135

What is the process of healing in rigid fracture repair?

Direct osteonal bridging of teh fracture 

136

What do osteoclasts do during rigid fracture repair?

Osteoclasts forming channels for new osteons will jump fracture line 

New osteons with will knit the bone ends together without formation of callus 

137

What are the five complications of fracture healing?

Inadequate blood supply 

Instability 

Infection 

Malnutrition 

Associated with implants 

138

What happens with fracture healing when there is an inadequate blood supply?

Hyaline cartilage will form 

-- or -- 

Necrosis if anoxia is present

139

What can cause instability during fracture healing?

Mechanical tension + compression 

Developments fibrous CT 

if there is excessive movement 

140

What are the problems associated implants in fracture repair?

Too large 

Blood supply damage 

Bacterial growth

141

What happens when a fracture implant is too big?

Deprive the bone of normal mechanical forces 

Leads to atrophy of disuse

142

What animals are at risk for arthrogryposis?

Cattle 

Sheep

143

What is arthrogryposis?

Congenital contracture of a joint 

Normally bilateral

144

What are the etiologies that can cause arthrogryposis?

Damage to the CNS

-- or -- 

Fetal paralysis caused by maternal intoxications

145

What viral infections can lead to arthrogryposis?

Akabane virus 

Bluetongue virus 

146

What can toxins can cause fetal paralysis?

Lupine plants - Anagyrine 

Poison hemlock - Coiine 

147

Who is hip dysplasia a major problem for?

Dogs

148

Describe: Hip dysplasia

Biomechanical disease 

Joint laxity of the hip = instability 

 

149

What does hip dysplasia result in?

Chronic subluxation 

Severe secondary DJD

150

Describe: DJD

Disease of synovial joints 

 

151

What can cause DJD to occur?

traumatic injury to the articular cartilage 

inflammation of synovium 

Abnormalities in conformation/jt. stability 

 

152

What are most cases of DJD secondary to?

Osteochondrosis 

153

What is the three cellular reasons for degeneration of intervertebral discs?

Loss of water + proteoglycans 

Hypocellularity 

Increase collagen content 

154

Where are cellular changes that lead to degeneration of the intervertebral disks occur?

Nucelus pulposus + Weakened annulus fibrosus

155

What happens to the IVD once cellular abnormalites occur?

Concentric/radial fissures in annulus 

Leads to buldging or herniation of nucleus pulposus material 

156

What occurs because of instability in the IVD?

Development of osteophytes at margins of vertebral margins 

-- -- or -- 

Adjacent disks 

157

158

Infectious arthritis (animal + presentation): Erysipleothrix rhusiopathiae

Pigs 

Septicemia leading to synovial joint + IVD lesions

159

Infectious arthritis (animal + presentation): trueperella pyogenes

Cattle + Pigs 

Suppurative arthritis 

160

Infectious arthritis (animal + presentation): Haemophilus parasuis

Piglets 

8 to 16 weeks 

Polyarthritis 

161

Infectious arthritis (animal + presentation): Borrelia burdogferi

Dog + Cattle + Horses 

Arthrtis 

Lyme disease

162

Infectious arthritis (animal + presentation): Mycoplasma hyorhinis

Pigs 

Weaning 

Fibrinous polyarthritis 

163

Infectious arthritis (animal + presentation): Mycoplasma bovis

Cattle 

Fibrinous to pyogranulomatous arthritis 

164

What are viral causes of arthritis?

Caprine arthritis 

Encephalitis virus 

165

What disease is responsible for noninfectious arthritis?

Crystal deposition disease 

166

What are the characterizations of crystal deposition disease?

Deposition of minerals such as urates + calcium phosphates 

within articular cartilage +/- soft tissue joints 

167

What speices lack the urease enzyme?

Primates 

Birds

Reptiles

168

What does uriase do?

Promotes oxidation of uric acid 

 

169