Bone Growth & Development

1
Bone Growth Development

• p. 134-139

2
Types of Bone Cells

• Osteocyte mature bone cell, enclosed in lacuna
• Osteoblast bone-forming cell secretes ECM of
  bone tissue (collagen fibers calcium salts)
• Osteoclast bone-destroying cell breaks down
  ECM to release calcium into the bloodstream

3
Fetal Bone Growth

• Bones of hyaline cartilage
• ECM is mostly collagen fibers
• Chondrocytes (in lacunae)
• Chondroblasts
• Chondroclasts

4
Ossification

• Cartilage is covered by bone internal hyaline
  cartilage is broken down

5
Epiphyseal Plates

• At birth, epiphyseal plates still made of
  cartilage
• (Also articular cartilage!)

6
Bone Growth Through Adolescence

• Controlled by growth hormone, and after puberty,
  sex hormones
• Longitudinal growth occurs at epiphyseal plates
• Completely ossified by end of adolescence

7
Continued

• Bones also grow in diameter along length of
  diaphysis
• Medullary cavity gets bigger
• Animation

8
Bone Remodeling

• Constant osteoblast osteoclast activity
  throughout life
• Causes
• Ca2 levels in blood
• If too low, parathyroid hormone activates
  osteoclasts
• If higher than needed, calcitonin (a hormone)
  activates osteoblasts
• Pull of gravity muscles
• Activates osteoblasts
• If not active, activates osteoclasts - atrophy

9

• Positive or negative feedback?????
• Ah, yes, its NEGATIVE!

10
Fractures

• Reduction realignment of bone ends
• Remember granulation tissue? During which step
  does it occur?
• New capillaries, phagocytes

11
Common Types of Fractures
12
Review

• Which cell type forms new bone?
• Which cell type destroys bone?
• Which cell type is a mature bone cell?
• What is the name of the bubble that a mature
  bone cell is enclosed within?
• What kind of tissue are fetal bones made of?
• What is ossification?
• What is the site of longitudinal bone growth
  called?

13

• Which hormones control bone growth through
  adolescence?
• Which hormones control bone remodeling? What does
  each one do?
• Distinguish between the three types of fractures.
• If a doctor reduces a fracture, what is she
  doing?
• Describe the four steps of bone repair after a
  fracture.