Endochonral Ossification

Front 1

enodochondral ossification

Back 1

osseous tissue is formed from hyaline cartilage
6 steps

Front 2

step one

Back 2

mesenchyme develops into a body of hyaline cartilage, covered with a fibrous periochodrium in the place of future bone. periochodrium produces chodrocytes, growing the cartilage in thickness.

Front 3

step 2

Back 3

periochodrium stops producing condrocytes, and begins producting osteoblasts. osteoblasts produce a bony collar. periochondrium is now consider periostium. chondrocytes enlarge forming lacunae making the matrix thin walls. Region of chondrocytes is the primary ossification center. walls of matrix calcify causing chondrocytes to lack nutrients and die. their lacunae form a single cavity in the middle

Front 4

step 3

Back 4

blood vessels penetrate bony colalre and invade promary ossification center. center become hollowed out and filled with blood forming the primary marrow cavity. various stem cells give rise to osteoblasts and osteoclasts. osteoblasts line cavity and begin depositing osteoid tissue, and calcify it to create bony trabeculae. bony collar thickens and elongates, causing a wave on condrocyte death toward the ends. osteoclasts follow this wave disolving cartilage reminants and enlarging he marrow cavity.
eventualy condrocyte growth and death form in epiphyses creating secondary ossification centers.

Front 5

step 4

Back 5

secondary ossification center is hollowed out creating secondary marrow cavity. lag between ossification centers at birth

Front 6

step 5

Back 6

epiphyses fill with spongey bone. the only cartilage left is the articular cartilage and the epiphyseal plate. serves as growth zone for bone elongation

Front 7

step 6

Back 7

by late teens to early 20s, cartilage in epiphyseal plate is gone closing the gap epiphyses and diaphyses.marrow cavities unite and bone cant grow in length any more.