2 Types of Ossifications

Endochondral Ossification creates...

All bones below head except clavicle

Step 3 of Intramembranous Ossification

1. Early Spongy Bone is formed as osteoblasts form trabeculae 2. Mesenchyme cells form periosteum and some forms red bone marrow

Step 2 of Intramembranous Ossification

1. Osteoblasts secrete organic matrix/osteoid, which calcifies. 2. Calcium salts and inorganic matrix/hydroxyapatite deposited in trabeculae during calcification. 3. Osteoblasts trapped in lacunae, become osteocytes

Step 2 of Endochondral Ossification

2. Bones begin to ossify from the outside 2A. Osteoblasts build bone collar on external surface 2B. Internal cartilage begins to calcify and chondrocytes die, leave lacunae

Step 1 of Intramembranous Ossification

A. Osteoblasts develop in the primary ossification center B. Mesenchymal Cells-->Osteogenic Cells-->Osteoblasts

Step 1 of Endochondral Ossification

Chondroblasts in perichondrium differentiate into osteoblasts Chondroblasts-->Osteogenic-->Osteoblasts Periosteum forms

Step 4 of Intramembranous Ossification

Early Compact Bone is formed beneath periosteum by osteoblasts

Intramembranous Ossification is based on model of...

Embryonic Connective Tissue

Intramembranous Ossification creates...

Flat bones of skull and clavicles

Endochondral Ossification is based on model of...

Hyaline Cartilage

Step 3A of Endochondral Ossification

In primary ossification center, osteoblasts replace calcified cartilage with early spongy bone; secondary ossification centers and medullary cavity develop

Step 3B of Endochondral Ossification

Medullary cavity enlarges due to ossification and epiphysis ossify. Remaining cartilage replaced with spongy bone. Filled with red bone marrow. Cartilage remains in epiphyseal plate and articular cartilage.