Lecture 3- Skeletal Activities Flashcards
Three main skeletal activities
Growth, modeling, remodeling
Bone growth by length
Endochondral ossification
Bone growth by width
Appositional growth
Primary ossification center
Forms in diaphysis
Secondary ossification center
Formed late in development in epiphysis; no medullary cavity, unlike primary ossification center
Where is cartilage not replaced by bone?
Epiphyseal growth plate and articular cartilage
Zones of articular cartilage
Resting cartilage
Proliferating zone
Hypertrophic zone
Primary spongiosa
Immature trabeculae on cancellous bone
Secondary spongiosa
Mature trabeculae
Bone modelling
Follows elongation of growth
Life-long process
Formation and absorption occurs at separate bone surfaces
Remodeling
Old bone resorbed by osteoclasts and new bone put down by osteoblasts at the same bone surface
Does not change shape or position of bone
Integral part of calcium homeostatic system
Steps in remodeling
- Resorption
- Reversal
- Formation
- Resting
Factors that impair bone fracture healing
Advanced age, poor nutritional status, inadequate blood supply, soft tissue between fractured ends of bone, inadequate immobilization, infection at fracture site
Arterial supply to long bones
Nutrient artery (marrow cavity)
Metaphyseal artery
Epiphysiseal artery
Periosteal artery
Direct bone healing
No callus formation
Occurs under conditions of absolute stability
Indirect bone healing
Requires fibrous/cartilaginous callus
Steps of indirect bone healing
Inflammation
Soft callus
Hard callus
Remodeling
Nonunions
Can be vascular (elephants foot) or avascular
