Skeletal Diseases

Question 1

Osteoblasts

Answer 1

Bone formimg cells that produce the organic matrix (single nuclei)

Question 2

Osteocytes

Answer 2

In lacunae
Regulates minute to minute Ca flux with osteoblasts

Question 3

Osteoclasts

Answer 3

Bone removing cells (multinucleate)
Restores bone by secreting H+ and metalloproteinases

Question 4

____________ is up inhibitor of osteoclasts

Answer 4

Calcitonin

Question 5

Endochondrial ossification

Answer 5

Bone forms and replaces a cartilage model

Question 6

Osteoclasts bone resorption

Answer 6

Activation of osteoblasts —> resorption of lamina limitans —> exposure of mineralized tissue for osteoclasts —> attachment of osteoclast and resorption

Question 7

What stimulates osteoclast activity?

Answer 7

PTH
Tension on bone
IL1, IL6, TNFa, PGE2a, RANK, Ligand

Question 8

Deformities/ anomalies of development

Answer 8

Abnorm. Modeling into appropriate shape
Inadequate growth during development
Defective endochondral ossification @ physis of articular- epiphyseal complexes
Genetic and acquired

Question 9

Types of chondrodysplasia and skeletal dysplasia

Answer 9

Dwarfism
Angular deformities (foals and sheep)
Amelia/ hemimelia
Skull/ mandible abnormalities (prognathism, brachygnathism, chiari malformation)

Question 10

What causes chondrodysplasia and skeletal dysplasia?

Answer 10

Genetic defects
Teratogens (veratrum californicum and thalidomide)
Nutritional abnormalities (iodine deficient goiter in foals)

Question 11

Osteochondrosis (dissecans)

Answer 11

Focal defect in endochondral ossification
Articular- Epiphyseal (AE) complex —> OCD
Disease of animals bred to rapid long bone growth

Question 12

Lesions associated with OCD

Answer 12

Plug of necrotic cartilage
Defect/ flap of articular cartilage
Uneven joint surface and subchondral bone

Question 13

OCD pathogenesis

Answer 13

Premature vessel closure —> AE ischemia —> cartilage necrosis —> necrotic cartilage breaks free into joint

Question 14

Loss of bone

Answer 14

Osteoclastic resorption exceeds bone production
Diffuse: osteoporosis and osteopenia
Focal: bone lysis

Question 15

Hyperostosis

Answer 15

↑ amount of bone production
Caused by compression, periosteal/ endosteal injury

Question 16

Osteosclerosis

Answer 16

Abnormally dense bone due to failure of osteoclasts (↓ # and activity of osteoclasts)

Question 17

Osteopetrosis

Answer 17

Diffuse osteosclerosis
Marble bone disease
Defective osteoclast bone resorption (no trabeculae)

Question 18

Fractures

Answer 18

Fx through the physis results in premature closure
Fx healing → callus formation
Remodeling

Question 19

Osteoporosis

Answer 19

Atrophy of bone (& mineralized cancellous bone)
↑ resorption than formation
Causes: lack of vit. D

Question 20

What causes osteoporosis?

Answer 20

Normal aging, malnutrition, excess Vit. A, deficiencies of Ca and P, disuse, parasitism, declining estrogen

Question 21

Gross lesions associated with osteoporsis?

Answer 21

↑ fragility
Reduction in cancellous bone and thinning of cortices of compact bone
Enlargement of marrow cavities

Question 22

Histo lesions associated with osteoporosis?

Answer 22

Reduction in #s of trabeculae
Abnormal activity of osteoblasts and osteoclasts

Question 23

Osteopenia

Answer 23

↓ in bone density and mass with no CS

Question 24

Osteomalacia

Answer 24

Softened bone (membranous bone formation)
In adult animals
Excessive bone resorption + unmineralized osteoid
Deficient in Vit. D or calcium

Question 25

Rickets

Answer 25

Softened, bowed bones (endochondral and membranous bone) In juvenile animals Failure of deposition of Ca salts in the matrixes Deficient in Vit. D or calcium

Question 26

Rickets pathogenesis

Answer 26

Chondrocytes proliferate and don't mature and degenerate → cartilage retained and widens growth plate

Question 27

Gross lesions of rickets

Answer 27

Enlargement of ends of long bones and costo-chondral articulations Epiphyseal cartilage wide Bones soft (severe)

Question 28

Fibrous osteodystrophy (FOD)

Answer 28

Prolonged hyperparathyroidism ↑ osteoclastic resorption of bone Deposition of immature fibrous tissue, IM and periosteal

Question 29

What causes Fibrous osteodystrophy?

Answer 29

Any mechanism that ↓ serum Ca: low dietary Ca, high dietary P, Vit. D deficiency, chronic renal failure

Question 30

Toxic osteodystrophies

Answer 30

Hypervitaminosis A and D Lead intoxication

Question 31

Lesions associated with Fibrous osteodystrophy

Answer 31

Diffuse osteoclastic bone resorption Proliferation of fibrous tissue in bone

Question 32

Nutritional FOD

Answer 32

↓ dietary Ca or ↑ dietary P ↓ Vit. D → ↓ serum Ca → ↑ PTH

Question 33

Species affected by nutrional FOD

Answer 33

Horses with high bran diet (High P) → big head disease Dogs, reptile with all meat diet (high P) Reptiles with all fruit diet (low Ca)

Question 34

Renal FOD

Answer 34

↓ TGFR → ↑ serum P (can't excrete) → ↓ D3 production ↓ serum Ca →↑ PTH → secondary soft tissue mineralization (nephrocalcinosis)

Question 35

Fibrous osterodystrophy is associated with __________

Answer 35

Parathyroid adenoma (check the kidneys and parathyroid glands!!)

Question 36

Gross effects of FOD

Answer 36

Bone pliable Changes in bones of face and mandible (thickened)- in horses and dogs

Question 37

Microscopic effects of FOD

Answer 37

Haversian canals enlarged Osteoclasts line receding bone Spaces OG with calcified bone now have fibrous CT

Question 38

Hypovitaminosis D

Answer 38

Physeal chondrodystrophy (Rickets) Osteomalacia FOD

Question 39

Osteonecrosis

Answer 39

Death of bone cells and medullary tissue Due to ischemia, bacterial toxins, heat and cold Necrotic bone in situ until osteoclastic removal

Question 40

Osteitis

Answer 40

Inflammation of the bone

Question 41

Periosteitis

Answer 41

Inflammation of the periosteum and medullary cavity

Question 42

Osteromyelitits

Answer 42

Inflammation of the medullary cavity and bone

Question 43

Parts of the joint capsule

Answer 43

Fibrous layer, loos fibrovascular layer and synoviocyte layer

Question 44

What makes up the articular cartilage?

Answer 44

Chondrocytes Collagen matrix Proteoglycan/ GAG matrix Water

Question 45

___________ is the nutritional source for chondrocytes

Answer 45

Synovial fluid

Question 46

Chondromalacia

Answer 46

Thinning and fibrillation of cartilage due to matrix loss ↑ wear and tear due to loss of lubrication

Question 47

Eburnation

Answer 47

Subchondral bone hyperstosis ↑ focal compression on subchondral plate due to loss of cartilage and abnormal joint loading

Question 48

Joint response to inflammation

Answer 48

Synovial villi hypertrophy ↑ synovial fluid volume ↓ synovial fluid viscosity Fibrinous exudate Neutrophil-rich exudate Neutrophil enzymes → cartilage erosion Septic artritis in more than one joint