intramembranous ossification step 1
An ossification center occurs within the embryonic tissue where mesenchymal cells cluster together, differentiate into osteoblasts, and secrete bone matrix. Some of the osteoblasts become trapped in the bone matrix and become osteocytes.
intramembranous ossification step 2
Blood vessels grow into the area to supply the cells and matrix with oxygen and nutrients. These blood vessels get trapped within the developing bone.
intramembranous ossification step 3
the bone assumes a foundation of spongy bone
intramembranous ossification step 4
remodeling creates compact bone and the finalized form of the bone
endochondral ossification step 1
cartilage cells differentiate into osteoblasts and secrete a bony collar around the diaphysis of the hyaline cartilage model
endochondral ossification step 2
a primary ossification center opens up and the cartilage at the center calcifies
endochondral ossification step 3
Blood vessels grow into the internal cavities. Fibroblasts within the blood vessels differentiate into osteoblasts. Osteoblasts secrete a spongy bone matrix down the length of the diaphysis.
endochondral ossification step 4
shortly before or right after birth, a secondary ossification center appears in the epiphyses
endochondral ossification step 5
The epiphysis ossify and the bone is remodeled (marrow cavity opens up and compact bone is formed) until the bone is in its final form. Some hyaline cartilage remains to form the articular cartilage and the epiphyseal cartilage seperating the epiphysis and the diaphysis.