Development of Bones

• Ossification


  the process by which bones form within the body.

  begins at sixth embryonic week until adulthood
• Blood cell production

  RBCs are produced by the red bone marrow (sternum, ribs, vertebrae, and pelvis)
• Intramembranous ossification


  when bone replaces membranes.

  occurs rapidly

  takes place in bones that are needed for protection (e.g. suture of the flat bones of the skullcap).
• Endochondral (intracartilaginous) ossification


  when bone replaces cartilage.

  much slower than intramembranous.

  occurs in most parts of the skeleton (long bones)
• Primary center (diaphysis)

  • the first center of ossification occurs in the midbody area.
  • they appear before birth
• Secondary centers (Epiphysis)

  • appear near the ends of the limbs of long bones.
  • they appear after birth.
• Epiphyseal plates


  cartilaginous plates found between the metaphysis and each epiphysis until skeletal growth is complete.
• Metaphysis

  • the wider portion of a long bone adjacent to the epiphyseal plate.
  • it is the area where bone growth in length occurs.