LEC 7 - Bone Flashcards
1
Q
What are the three cell types responsible in the maintaince and construction of bone?
A
Osteoblasts
Osteocytes
Osteoclasts
2
Q
Where do osteoclasts orginate from?
A
Hematopoietic stem cells
3
Q
What is the function of osteoclasts?
A
Responsible for bone resorption
Attach to mineralized bone surface
4
Q
Where are osteocytes located?
A
Osteoblasts that have been surrounded bu mineralized osteoid
Occupying small clear spaces called lacunae
5
Q
Where do osteoblasts arise from?
A
Mesenchymal cells
6
Q
What is the function of osteoblasts?
A
Initiate mineralization
Produce matrix
Initiate resorption of the resorption by osteoclasts
7
Q
What do osteocytes and osteoblasts control together?
A
Calcium homeostatisis
8
Q
In what direction does bone grow?
A
In length by intersitial growth
Within metaphyseal growth plates
9
Q
Describe: Endochondral ossification
A
Process in which bone desposited at mineralized longitudinal septa of the physes
10
Q
How many zones are there in the physes?
A
3
11
Q
What are the three physeal zones?
A
Resting
Proliferative
Hypertrophic
12
Q
Describe: Resting Zone
A
Source cells for proliferative zone
13
Q
Describe: Proliferative zone
A
Cell multiply
Accumulate glycogen
Produce matrix and become arranged in longitudinal columns
14
Q
Describe: Hypertrophic zones
A
Chondrocytes secrete macromolecules to allow capillary invasion and initiate matrix calcification
15
Q
What are the two sub-zones of hypertrophic zones?
A
Maturation
Degeneration
Calcification
16
Q
How does growth of epihysis occur?
A
Endochondral ossification at articular-epiphyseal complexes
(AEC)
17
Q
What is the AEC composed of?
A
Articular cartilage
Subajacent temporary growth cartilage
18
Q
How does bone grow in width?
A
Intermembranous bone formation
19
Q
What is the surfaces of bone covered by?
A
periosteom
20
Q
What is periosteom made from?
A
Loosely attached membrane
Outer fibrous layer = structural support
Innter osteogenic layer = normal lamellar apossitional bone
21
Q
What type of bone is laid down in response to injury?
A
Abnormal woven bone
22
Q
What hormonal agents are released in response to insult on the bone?
A
Calcitrol
PTH
23
Q
What are two examples of disruption of endochondral ossification?
A
Growth arrest lines
Growth retardation lattice
24
Q
Describe: Growth arrest lines
A
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
