Endochondral Ossification Flashcards
First 3 steps of EO
Hyaline cartilage grows Apositionally and interstitially and is the blueprint for EO
At a genetically pre-determined stage, periosteal bony collar forms within the perichondrium via Intramembranous ossification
As the periosteal collar mineralizes, perichondrium becomes periosteum and compact bone is laid down on the outer surface of the shaft
2 steps after perichondrium becomes Periosteum
The periosteal bony collar extends to the epiphysis and chondrocytes stack and then enlarge in size, becoming hypertrophic cartilage (can begin calcifying)
The presence of periosteal bony collar and calcification inhibits oxygen and nutrients from diffusing to the skeleton
2 Steps after diffusion of nutrients and and oxygen is inhibited
The diaphysis is inhibited by a periosteal bud made of blood vessels, Mesenchymal cells, and chondro/osteoblasts. This establishes the primary ossification center
Chondro/osteoclasts secrete enzymes that degrade hypertrophic cartilage and Mesenchymal cells differentiate into cells of primitive bone marrow and osteoblasts
What happens after Mesenchymal cells begin differentiating and osteoclasts degrade
Vascularization and degradation of the hypertrophic cartilage establishes the marrow cavity and osteoblasts are deposited
The secondary ossification center forms at the epiphyses and contains 5 cartilaginous growth plate zones
Growth plate zones
Resting zone
Zone of proliferation
Zone of hypertrophy
Zone of degradation
Zone of ossification
Once the growth plate and zones are established, what happens
Transition from hypertrophic cartilage to bone and marrow continues within the growth plate and is responsible for longitudinal growth
What happens when the growth plate closes and is any cartilage left
Growth plate closure terminates longitudinal bone growth
In adults, no cartilage is left except the hyaline articular cartilage around the epiphyses (they lack perichondrium)
