Intramembranous Ossification: Step One: Development of Ossification Center
Osteoblasts secrete organic extracellular matrix
Intramembranous Ossification: Step Two: Calcification
Calcium and other mineral salts are deposited and extracellular matrix calcifies (hardens).
Intramembranous Ossification: Step Three: Formation of Trabeculae
Extracellular matrix develops into trabeculae that fuse to form spongy bone
Intramembranous Ossification: Step Four: Development of the Periosteum
Mesenchyme at the periphery of the bone develops into the periosteum.
Endochondral Ossification: Step One: Development of the Cartilage Model
Mesenchymal cells develop into chondroblassts which form the cartilage model.
Endochondral Ossification: Step Two: Growth of Cartilage Model
Growth occurs by cell division of chondrocytes.
Endochondral Ossification: Step Three: Development of Primary Ossification Center
In this region of the diaphysis, bone tissue replaces most of the cartilage.
Endochondral Ossification: Step Four: Development Of the Medullary (Marrow) Cavity
Bone breakdown by osteoclasts forms the medullary cavity.
Endochondral Ossification: Step Five: Development of Secondary Ossification Centers
These occur in the epiphyses of the bone.
Endochondral Ossification: Step Six: Formation Of Articular Cartilage and Epiphyseal Plate
Both structures consist of hyaline cartilage.
Ossification Center
Mesenchymal cells cluster together and differentiate (First into osteogenic cells and then into osteoblasts). This is the area where cells cluster.
Cartilage Model
Consists of Hyaline cartlage. Produced by chondroblasts secreation of cartilage extracellular matrix.
Perichondrium
Develops around the cartilage model.
Interstitial (Endogenous) Growth
A type of cartilaginous growth. Growth from within. Results in an increase in length.
Appositional (Exogenous) Growth
Growth at the outer surface. Growth of the cartilage in thickness because extracellular matrix material is deposited on the cartilage surface of the model by chondroblasts.
Periosteum
Once the perichondrium starts to form bone
Primary Ossification Center
A region where bone tissue will replace most of the cartilage.
Secondary Ossification Centers
When branches of the epiphyseal artery enter the epiphyses. Spongy bone remains in the interior of the epiphyses and no medullary cavities are formed here. Ossification proceeds outward from the center towards the outer surface.
Epiphyseal (Growth) Plate
A layer of Hyaline cartilage in the metaphysis of a growing bone that consists of four zones.
Zone Of Resting Cartilage
The topmost layer and nearest the epiphysis and consist of small, scattered condrocytes.
Zone Of Proliferating Cartilage
The second layer from the top, Slightly larger chondrocytes in this zone are arranged like stacks of coins. Undergo interstitial growth as they divide and secrete extracellular matrix. Also Chondrocytes in this zone divide to replace those that die at the
Zone of Hypertrophic Cartilage
The third layer. This layer consist of large, maturing chondrocytes arranged in columns.
Zone of Calcified Cartilage
The final zone. Only a few cells thick and consists mainly of dead chondrocytes because of matrix surrounding them are calcified.
Epiphyseal Line
When the epiphyseal plate fades leaving a bony structure called this ______.