General Bone and joints Flashcards
What cell produces osteoid?
Osteoblasts
What does Alk Phos correlate with?
Osteoblast activity
What is the role of Osteocytes?
Detect changes in bone stress
Mechanism of Bone resorption
PTH binds O-blasts –> retract from bone surface
- -> O-clast attach surface
- -> RANK Lig (O-blast) binds RANK receptor (O-clasts) –> stimulates Carbonic acid & collagenases secretion
- -> acid dissolves mineral / collagenases break down osteoid
What promotes osteoclastic activity?
IL1, TNF alpha, PTH
What inhibits osteoclastic activity?
Calcitonin
Organic Matrix composition
- Type 1 collagen
- proteoglycans
- GAGs
- Lipids
-Synth by O-blasts
Arrangement of compact bone
- Concentric lamellae
- Osteons (haversian system)
- Function:
- Reduces propagation of micro cracks = bone strength!
Arrangement of Trabecular bone
- Parellel lamellae
- Mechanical stress
Bone Mineral
Hydroxyapatite crystals deposited in collagen fibers
What is a cement line
- Proteoglycan rich seams in remodeling or modeling units
Modeling Vs Remodeling
Modeling
- change shape or contour of bone
- in response to normal growth or dz
- change in external pressures
Remodeling
-Resorption of old bone –> replaced by new bone
Reversal lines
Scalloped cement lines
-indicates previous resorptive activity
Resting cement lines
Smooth lines
-where bone formation temporarily stopped
Describe intramembranous ossification
Mesenchymal cells differentiate to O-blasts
–> flat bone formation
-also long bones (width)
Zones of growth plate in Endochondral ossification
Resting
Proliferative
Hypertorphic
Post mortem Bone exam
- Use same long bone always
- -Marrow fat stores / hematopoietic activity
- -Cortical bone (thickness)
- -Trabecular bone (amt/distribution)
- -Metaphyseal plates (Thickness-young animals)
- -Articular surfaces
- -Tendons/ligaments
- Compare gross changes w/ rads
- *Autolysis less severe than other tissues
Post mortem Joint exam
Open several joints MEDIAL aspect
- -EXCEPT for stifle
- Check synovial fluid
Important components of synovial fluid
- viscosity
- color
- volume
Growth Arrest lines
- Parallel lines
- involving primary trabeculae
- malnutrition
Growth Retardation lattice
- Dense band of vertically oriented trabecular bone near growth plate
- failure of osteoclastic bone resorption
Retention of primary trabeculae

Causes for Premature growth plate closure
- Hypervitaminosis A
- Mn deficiency
- inflammation
- vascular trauma
According to Wolff’s law, compression…
–> bone formation
Tension –> resorption
When is Woven bone normal?
= Immature bone, so Young animals
-pathologic in adults
What is Periostium’s response to injury?
- Formation of woven bone
- perpendicular to the long axis of the bone - Cartilage present if oxygen tension is low
