Bone Development _during fetal development_ - AnatomyFreaks by hcj


									          Bone Development
                 (during fetal development)

• Intramembranous ossification
  – Takes place in connective tissue membrane
• Endochondral ossification
  – Takes place in cartilage
• Both methods of ossification
  – Produce woven bone that is then remodeled
  – After remodeling, formation cannot be
    distinguished as one or other

    Intramembranous Ossification
                     (8th week – 2 years of development)

•   Takes place in connective tissue membrane
    formed from embryonic mesenchyme
•   Forms many skull bones, part of mandible,
    diaphyses of clavicles
•   When remodeled, indistinguishable from
    endochondral bone.
•   Centers of ossification: locations in membrane
    where ossification begins (centers of ossification expand
    outwards to form a bone by gradually ossifying the membrane)
•   Fontanels: large membrane-covered spaces
    between developing skull bones; unossified (bones
    eventually grow together & all fontanels have closed by 2 years of age)
Intramembranous Ossification

      Endochondral Ossification
• Bones of the base of the skull, part of the
  mandible, epiphyses of the clavicles, and most
  of remaining bones of skeletal system
• Cartilage formation begins at end of fourth
  week of development
• Some ossification beginning at about week
  eight; some does not begin until 18-20 years
  of age

Endochondral Ossification

Endochondral Ossification

Endochondral Ossification

Endochondral Ossification

         Growth in Bone Length
• Growth in length occurs at the epiphyseal plate
• Involves the formation of new cartilage by
   – Interstitial cartilage growth
   – Appositional growth on the surface of the cartilage
• Closure of epiphyseal plate: epiphyseal plate is
  ossified becoming the epiphyseal line. Between
  12 and 25 years of age
• Articular cartilage: does not ossify, and persists
  through life
• Appositional growth only
   – Interstitial growth cannot occur because matrix is solid
   – Occurs on old bone and/or on cartilage surface

To top