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VETM 425 Sys Path > Lecture 28: MSK 1 > Flashcards

Lecture 28: MSK 1 Flashcards

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1
Q

List 3 cell types in bone and their respective origin?

A

osteoblasts: mesenchymal cells on bone surface
- immature

osteocytes: mature osteoblasts that are found in lacunae surrounded by ECM
- cannaliculi allow communication

osteoclasts: multinucleated hematopoietic cells formed from the fusion of monocyte/macrophages
- found on bone in howships lacunae

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2
Q

What is the function of osteoblasts

A

make osteoid and initiate mineralization

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3
Q

What is the function of oseocytes

A
  • stimulate formation and resorption of bone in response to mechanosensation
    make regulatory factors and regulate Ca/P homeostasis
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4
Q

What is the function of osteoclasts

A

resorb bone via acid hydrolases

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5
Q

What is extracellular matrix of bone made out of

A

hydroxyapetite - inorganic
- Ca/P
- other minerals: carbonate/Mg/Zn/Ca

osteoid - organic
- 90% type 1 collagen
- glycoproteins

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6
Q

What is the periosteum

A

The outer fibrous layer containing blood and nerves

inner cambrium layer is osteogenic and spindle shaped

It is separated from bone by the layer of osteoblasts

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7
Q

Compare and contrast woven bone and lamellar bone

A

woven bone aka reactive or new bone
- immature (young or remodelling)
- disorganized collagen

lamellar
- mature
- concentric collagen lamellae
- long term stability

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8
Q

Compare and contrast compact and cancellous bone

A

compact aka cortical bone
- high density (lamellar or woven)
- cortex and subchondral plate

cancellous aka trabecular or spongey bone
- low density (lamellar or woven bone)
- medulla

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9
Q

What is intramembranous ossification? Provide examples of bones formed this way

A

Bone forming from the mesenchymal tissue

no cartilage precursor

ex. flat bone of the skull
form the periosteal surface of all bones

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10
Q

What is endochondral ossification

A

Bone forming from a cartilage precursor/ossification center

aka physeal growth - from a growth plate

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11
Q

What is a physis? What are the 3 main zones of a physics?

A

growth plate

reserve/resting zone: lazy chondrocytes
proliferative: active chondrocytes, accumulate glycogen
- lengthening
hypertrophic: old chondrocytes - becoming mineralized

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12
Q

What characterizes the epiphysis?

A

It is capped by trabecular bone

no bone growth on this side of the physis

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13
Q

What characterizes the metaphysis

A

Bone growth occurs on this side of the physics

It has primary spongiosa: the blueprint for bone growth
- there is an abrupt demarcation between the physis and hypertrophic regions
- spiracules of mineralized cartilage from the scaffhold

secondary spongiosa is remodelling

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14
Q

What are 5 reactions to injury bone can have

A

necrosis

change trabeculae

change size/shape/mass

produce new bone

periosteal reaction

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15
Q

What can cause bone necrosis?

A

Reduced or blocked blood supply

osteocytes phagocytose necrotic bone

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16
Q

What are 2 consequences of bone necrosis?

A

sequestrum: mummified necrotic bone
- it leaves just mineral

involucrum: sequestrum surrounded by fibrosis/osseus and granulation tissue
- form bone cyst

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17
Q

What can cause bone to change its trabeculae? What is the result?

A

disruption of the endochondral ossification at the physis - alter the appearance of the primary spongiosa
- due to trauma/damage - salter harris fx

it causes premature close of the growth plate
- either focal or complete resulting in asymmetrical or symmetrical reduced elongation of the bone

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18
Q

What is wolffs law

A

bone will adapt to use

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19
Q

What is remodelling? What are the types of remodelling

A

normal process of bone replacement

if it is normal there is no change in shape or amount of bone made

primary: resorption and replacement of bone in growth

secondary: continuous replacement through life

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20
Q

What can cause a bone to produce more bone? What kind of bone does it produce?

A

In normal fetal development this occurs

can also be stimulated by irritation
- bone formation in a mature skeleton is abnormal

forms woven bone

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21
Q

What is hyperosteosis

A

excess production of bone

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22
Q

What is a periosteal reaction bone can have

A

woven bone production that is perpendicular to the long axis of the cortex

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23
Q

What is exostosis

A

hyperoseosis

osteophyte formation
- restricted to periarticular new bone
- ‘ knobs around joint’

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24
Q

Compare and contrast the 2 types of fractures

A

traumatic: normal bone experiencing excess force (trauma)

pathologic: abnormal bone experiencing normal force
- osteomyelitis (T. pyogenes)
- neoplasia
-metabolic dz

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25
What are 2 main factors that fx repair depends on
stabilization and complications
26
What are the 4 stages of fracture repair
1. hematoma: inflammation within days of injury 2. soft/primary callus: fibroblasts and cartilage form in days-weeks 3. hard/secondary callus: woven bone replacing cartilage 4. remodelling: lamellar bone replacing woven bone, shrinking callus
27
What can you infer from the size of the fx callus
it indicated the stability larger callus = less stable fx smaller callus = more stable fx hyperplastic callus can complicate diagnostic interpretation
28
What is a salter harris fracture
A fracture in a young animal that affects their growth plate it mainly affects the physis because that is the weakest point = most likely to break
29
What are 4 major factors that contribute to fracture complications
1. instability: inhibiting hard callus formation - can lead to pseudoarthrosis (false joint) 2. reduced blood supply: causing osteonecrosis and sequestrum formation 3. infection: bacterial osteomyelitis 4. systemic disease: malnutrition or cachexia
30
A young animal is brought in to you with a long bone fracture. What fracture type do you expect to see?
a type 2 salter harris fracture - through the growth plate and metaphysis this is the most common type of salter harris fracture
31
Compare the complication rate of the different types of salter harris fractures
least complications with type 1 and 2 salter harris type 3, 4, 5 can permanently damage the physis type 3 and 4 can cause angular limb deformities - valgus or varus
32
Compare valgus and varus
valgus - lateral deviation of the distal limb varus - medial deviation of the distal limb
33
List 5 causes of angular limb deformity
trauma cartilage deformity malposition in utero joint laxity hypothyroidism
34
What is epiphysiolysis? Why does it occur?
separation of the epiphysis due to high amounts of shear forces - transphyseal fissure - underlying dysplasia
35
Give examples of epiphysiolysis in cat, pig, and dog
cat: slipped capital femoral epiphysis pig - gilt - femoral head - sow - ischial tuberosity dog - un-united aconeal process
36
What is the function of parathyroid hormone
increase blood Ca reduce blood P cause bone degredation - increase excretion of P and absorption of Ca
37
What is the function of calcitonin
decrease blood Ca and P increase bone density (PTH antagonist)
38
What is the function of vitamin D
increase blood Ca and P causes reduced PTH and increased resorption in kidneys and intestines - increase osteoclast activity
39
What is the function of fibroblast growth factor 23?
reduce blood P cause increase PTH and inhibition of vitamin D synthesis
40
What are 3 general categories of dysfunction that result in osteodystrophies?
failure of producing bone mineralization maintenance of bone
41
What 2 main factors contribute to metabolic bone disease
nutrition hormones
42
What is osteoporosis
reduced amount of normal bone - bone resorption exceeds bone prod bone is porous, thin, and brittle retains. abnormal shape
43
When is osteoporosis diagnosible via radiographs
When there is a minimum of 30% bone loss early stages are often missed
44
What type of lesion is osteoporosis associated with commonly
pathological fractures loss of trabecular bone preferentially also loss of bone cortices
45
What is the most common metabolic bone disease
osteoporosis
46
What are 6 major causes of osteoporosis
malnutrition Gi parasitism secondary to lactation malabsorption (chronic IBD) starvation disuse - wolffs law
47
Define serous atrophy of fat? What does this indicate? What is the common lesion affecting bone?
It is the preferential use of fat from body compartments due to a negative energy balance SC > visceral > bone marrow It causes watery and gelatinous bone marrow
48
What are growth arrest lines? What causes them?
It is disruption in endochondral ossification due to a transient decrease in growth. It causes a temporary sealing of the growth plate - can visualize in the trabecualr parallel to the physis - as growth continues this line will be carried into the metaphysics due to malnutrition or debilitation (ex. BVD/distemper)
49
Compare osteomalacia and ricketts
Osteomalacia - mature animals - occurs in areas of remodelling Ricketts - young animals - in growth plates They are both due to problems with mineralization - vitamin D or P deficiency
50
List 2 common disease conditions that can occur due to calcium deficiency
fibrous osteodystrophy osteoporosis It will not cause ricketts or osteomalacia
51
What is the gross lesions associated with osteomalacia
unmineralized osteoid that persists
52
What are the gross lesions of ricketts
irregular thickening tongues of cartilage in the metaphysis enlargement of the costochondral junctions - rachitic rosary soft and malleable bone
53
What is a characteristic histologic feature of ricketts
Persistent hypertrophic chrondrocytes - normally they would initiate mineralization and apoptosis
54
List 4 causes of vitamin D deficiency
reduced UV light vitamin D anatagonist ingestion (plant) reduced dietary intake congenital
55
What is fibrous osteodystrophy? Why does it occur?
It is the replacement of bone with fibrous tissue and woven bone occurs in adults due to chronically high PTH
56
List 2 causes of primary hyperparathyroidism and what is a common sequelae
parathyroid tumor pseudohyperparathyroidism (hypercalcemia of malignancy) both result in fibrous osteodystrophy
57
What are 2 types of secondary hyperparathyroidism and what is a common sequelae
renal nutritional both cause fibrous osteodystrophy
58
How does nutrition cause hyperparathyroidism? What species does it affect?
if there is an imbalance in the Ca:P ratio - high P + low Ca dogs/cats: all meat diets horses/goats: high grain/cereal/oxalate diet cause FOD sheep/cows - nutritional hyperparathyroidism will cause osteoporosis not FOD
59
A horse presents to you with a history of a high cereal grain diet and bilateral swelling of maxillary bones. What is your top differential? Why?
bighead disease due to nutritional secondary hyperparathyroidism it causes the bilateral swelling of the maxillary bones because horses are always chewing can also cause displaced/loose teeth and compression of nasal passages
60
Describe the pathogenesis of renal secondary hyperparathyroidism
1. CKD 2. low GFR 3. P retained (should be excreted) 4a. C and P precipitate (low blood P) 5a. Stimulate parathyroid = high PTH 4b. high fibroblastic growth factor 23 5b. reduced vitamin D
61
What are the gross features of fibrous osteodystrophy
swollen and weak bones normal physis - except if young with low vitamin D and concurrent ricketts
62
What animals are susceptible to vitamin A (retinol) deficiency? Why
cattle and pigs if given unsupplemented ration or if given old hay (vit A will decrease over time)
63
What are the gross and clinical consequences of vitA deficiency?
causes defective remodelling of membranous bone - asynchronous skull development causing - micropthalmia - blindness due to optic foramina narrowing - cerebellar herniation through foramen magnum because braincase doesn't grow
64
What is the pathological and clinical consequences of vitC (ascorbic acid) deficiency
impairs collagen synthesis and osteoblast differentiation causing bleeding
65
What 3 animals are primarily prone to vitC deficiency?
humans guinea pigs cetaceans

VETM 425 Sys Path (38 decks)

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