Osseous Tissue (Bone Tissue)

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Osseous Tissue (Bone Tissue)
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1. Cells

• Osteocytes mature bone cells
• Osteoblasts bone-forming cells (germ cells or
  bud cells)
• Osteoclasts bone-destroying cells (breakers)
• A. primarily collagen fibers
• flexibility
• tensile strength (the strength to endure
  stretching forces)
• B. calcium salts (hardness)
• contain calcium and phosphorus
• great compressional strength (the strength to
  endure squeezing forces)

2. Matrix
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Bone Remodeling

• constant balance of bone deposit and removal that
  occurs throughout your life
• bone deposit occurs at a greater rate when bone
  is injured
• bone reabsorption allows calcium of degraded bone
  matrix to move into the blood.

About 10 of bone is replaced every year in an
adult skeleton
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Maintenance of Bone
boneformation
bonereabsorption
osteoblasts
osteoclasts
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Calcium Negative Feedback Cycle
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• Control of Remodeling
• Hormonal                                          
               
•  Rising blood Ca2 levels trigger the thyroid to
  release calcitonin 
•  Calcitonin stimulates calcium salt deposit in
  bone 
•  Falling blood Ca2 levels signal the parathyroid
  glands to release Parathyroid hormone (PTH) 
•  PTH signals osteoclasts to degrade bone matrix
  and release Ca2 into the blood 

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Hormonal effects
boneformation
bonereabsorption
osteoblasts
osteoclasts
Calcitonin (CT)from thyroid
Parathyroidhormone (PTH)from parathyroid
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Increase bone mass
boneformation
bonereabsorption
osteoblasts
osteoclasts
Before age 25
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boneformation
bonereabsorption
osteoblasts
osteoclasts
Age 25-50
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Decrease bone mass
boneformation
bonereabsorption
osteoblasts
osteoclasts
Age 50-on
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Bone Loss with Age
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Stress effects
boneformation
bonereabsorption
osteoblasts
osteoclasts
Stress increases bone density
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http//www.youtube.com/watch?vyFJ4iswRiu4feature
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