Ossification = Osteogenesis

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Ossification Osteogenesis
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Ossification Osteogenesis

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

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There are two classifications of
ossification Intramembranous
Endochondral Replacement of Replacement of
sheetlike connective hyaline
cartilage tissue with bony tissue with bony
tissue Primarily in flat bones Most
bones are of skull some irregular formed
this way bones
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Intramembranous Ossification
Osteoblasts migrate to the membrane and deposit
bony matrix around themselves. Once surrounded by
matrix, they are called osteocytes.
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Endochondral Ossification

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

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Endochondral Ossification

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

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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
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Secondary Growth Center
Epiphyseal Plate ? Line
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Epiphyseal Growth
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Appositional Growth
Although bone length growth stops in the 20s,
bones can continue to increase in thickness or
diameter throughout life in response to stress
from increased muscle activity or weight.
Osteoblasts in the periosteum form compact bone
around the external bone surface Osteoclasts in
the endosteum break down bone around the
medullary cavity