Bone Formation, Growth, and Remodeling

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Bone Formation, Growth, and Remodeling

• Chris Symans, Calli Goodnoe, and Kaitlyn Karpinski

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Bone Formation

• The skeleton is made of bone and cartilage.
• In embryo, the skeleton is made of hyaline
  cartilage.
• As the child ages, the hyaline cartilage is
  replaced by bone tissues through ossification.

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Ossification

• Ossification occurs in two major steps.
• Step 1 the hyaline cartilage model is completely
  covered with bone matrix by osteoblasts.
• osteoblasts are bone-forming cells.
• Step 2 The articular cartilage covers the end of
  bones and lasts throughout life. The epiphyseal
  plates also remain as cartilage to provide room
  for longitudinal bone growth throughout
  childhood. They are then ossified into compact
  bone.

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How Growth is Controlled

• The process of bone growth is controlled by two
  major hormones.
• Growth Hormones- the most important part
• Sex Hormones- which become active during puberty.
• Bone growth ends after adolescence when the
  epiphyseal plates become fully fused.

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Dynamic Bone

• Bone is dynamic, or active. Bones are remodeled
  continuously in response to two factors
• Calcium levels in the blood and
• The pull of Gravity and Muscles on the skeleton.

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Calcium

• When blood calcium levels drop, the parathyroid
  glands release parathyroid hormone into the
  blood.
• The PTH activates osteoclasts, which break down
  bone cells and release calcium into the blood
  stream.
• On the other hand, when calcium levels are too
  high, calcium is deposited into bone matrix as
  hard calcium salts.

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Gravity

• Gravity applies a constant force on the body. To
  compensate for this force, the bones must become
  stronger.
• At the same time the muscles are always applying
  forces across the skeleton.
• Thus to compensate for these forces, the bones
  must become stronger themselves.

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Bone Remodeling

• In order to retain normal proportions and
  strength, during bone growth the Skeleton becomes
  denser and develops projections to compensate for
  stress.
• At such sites osteoblasts lay down new bone
  matrix and are trapped within it. They then
  become osteocytes, or mature bone cells.

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The End
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Works Cited

• Google Images
• Essentials of Human Anatomoy Physiology by
  Elaine N. Marieb