Endochondral ossification Flashcards
When does it begin
fetus
What bones does it make
all but flat
What does it start with
Hyaline cartilage model
What is the 1st step
Primary ossification centre forms in mid region.
What happens at the primary ossification centre
1) chondroblasts build cartilage model, covered by perichondrium
2) Chondroblasts hypertrophy
3) Cartilage calcifies
4) chondroblasts die, leaving empty lacunae
5) Nutrient artery enters w/ osteogenic cells
6) Osteogenic into osteoblasts
7) Osteoblasts build bone matrix on lacunae
8) Primary ossification centre forms in mid region
9) Perichondrium becomes periosteum
10) forms thin layer of compact bone around spongy bone center
What is step 2
Medullary cavity forms
What happens when the medullary cavity forms
1) Osteoclasts remove spongy bone in mid-region to form medullary cavity
2) osteoblasts remodel spongy bone into compact bone
3) osteoclasts and osteoblast form endosteum (lines medullary
4) BV in medullary cavity forms the red bone marrow
What is step 3
Secondary ossification centers form in the ends (around time of birth) (Same things repeats in the ends)
What is Step 4
Cartilage remaining at bone ends becomes articular 1
What is step 5a
Cartilage remaining at epiphysis growth plate allows for lengthening
How does bone lengthening work
There are resting cartilage, dividing cartilage which produce more and maintain the place, hypertrophying cartilage where the chondrocytes swell and die and calcifying cartilage where the osteogenic cells enter and lay new bone to make it grow longer.
What is step 5b
Bones thicken by appositional growth
What is appositional growth
- osteoclasts in endosteum remove matrix to make a bigger medullary cavity
- Osteoblasts in periosteum add bone in circumferential lamellae
- circumerential lamellae are remodelled into osteons for better nutrient supply
