Ossification = Osteogenesis

Ossification = Osteogenesis

Ossification = Osteogenesis Parts of the fetal skeleton form during the first few weeks after conception By the end of the 8 th week, the skeletal pattern is formed : cartilage & connective tissue membranes

There are two classifications of ossification: Intramembranous: Endochondral: *Replacement of sheetlike connective tissue with bony tissue *Primarily in flat bones of skull & some irregular *Replacement of hyaline cartilage with bony tissue *Most bones are formed this way bones

Intramembranous Ossification Osteoblasts migrate to the membrane and deposit bony matrix around themselves.

Intramembranous Ossification Osteoblasts migrate to the membrane and deposit bony matrix around themselves. Once surrounded by matrix, they are called osteocytes.

Intramembranous Ossification Osteoblasts migrate to the membrane and deposit bony matrix around themselves. Once surrounded by matrix, they are called osteocytes. Islands of bone grow outward from the origin and connect with one anaother

Intramembranous Ossification Osteoblasts migrate to the membrane and deposit bony matrix around themselves. Once surrounded by matrix, they are called osteocytes. Islands of bone grow outward from the origin and connect with one anaother After formation, growth continues only from border cells

Endochondral Ossification Hyaline cartilage bones are infiltrated with blood vessels & osteoblasts. Formation of periosteum Collar of compact bone around diaphysis

Endochondral Ossification At the same time, cartilage in center of diaphysis begins to disintegrate Replaced with spongy bone * Primary Ossification Center*

Ossification continues from the primary ossification center towards the ends of the bones.

Ossification continues from the primary ossification center towards the ends of the bones. After spongy bone is formed in diaphysis, osteoclasts break it down to open up medullary cavity

Ossification continues from the primary ossification center towards the ends of the bones. After spongy bone is formed in diaphysis, osteoclasts break it down to open up medullary cavity The cartilage in the epiphysis continues to grow, so developing bone increases in length

Ossification continues from the primary ossification center towards the ends of the bones. After spongy bone is formed in diaphysis, osteoclasts break it down to open up medullary cavity The cartilage in the epiphysis continues to grow, so developing bone increases in length After birth, secondary ossification centers form in epiphyses ossification is similar, except spongy bone is not broken down.

Ossification continues from the primary ossification center towards the ends of the bones. After spongy bone is formed in diaphysis, osteoclasts break it down to open up medullary cavity The cartilage in the epiphysis continues to grow, so developing bone increases in length After birth, secondary ossification centers form in epiphyses ossification is similar, except spongy bone is not broken down. Once ossification is complete the cartilage is all replaced except at the surface of the epiphysis [articular cartilage] and between the diaphysis and epiphysis [epiphyseal plate]