Bone tissue

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Bone tissue

• Anatomy of a bone
• Structure of bone tissue
• Formation and growth of bone
• Fracture and repair
• Effects of physiological processes on bone

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The parts of a long bone

• Diaphysis-shaft
• Epiphyses- ends
• Come together at metaphyses
• Articular cartilage protects epiphyses
• Periosteum covers bone
• Medullary cavity contains marrow is lined by
  endosteum

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Bone cells
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Organization of bone tissue
compact
spongy
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Compact vs. spongy bone

• Compact bone
• External layer
• Arranged in osteons
• Lamellae are found around periphery and between
  osteons
• Central canals connected to each other by
  perforating canals

• Spongy bone
• No osteons
• Arranged in trabeculae
• Major type of tisse in short, flat, irregular
  bones
• Much lighter than compact bone
• Supports red bone marrow

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Blood and nerve supply to bone

• Abundant supply of blood
• May have several nutrient arteries
• Nerves accompany blood vessels

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Ossification (osteogenesis)

• Bone forms within mesenchyme in layers
  (intramembranous)
• Flat bones of skull and mandible
• Osteocytes secrete calcium
• Compact and spongy bone form

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Endochondral ossification

• Most bones are formed this way
• Calcification is triggered when chondrocytes die
• Vascularization triggers ossification

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Bone growth in length (epiphyseal plate)

• Growth is on epiphyseal side
• Resting cartilage secures epiphyseal plate
• Dividing cells are in proliferating cartilage
• Cells mature in hypertrophic cartilage
• Osteoblasts replace calcified cartilage

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Bones get thicker by appositional growth

• Osteoblasts form new extracellular matrix
• Blood vessel becomes enclosed, supports new
  osteon
• Osteoblasts lay down extracellular matrix

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Bone remodeling replaces old tissue

• Resorption by osteoclasts, deposition by
  osteoblasts
• Strengthens bone
• Repairs damaged bone

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Types of fracture
Stress fracture is not visible Overuse or
degeneration
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Process of fracture repair
Bone grows slowly blood supply may be affected
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Life processes and bone formation

• Why is exercise good for bones?
• How does aging affect bones?
• Loss of bone mass due to calcium loss
• Decreased production of collagen

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Treatment of osteoporosis

• Prevention
• Steroid hormone replacement (stimulates
  osteoblast activity)
• Evista has estrogen-like effects on bone
  formation
• Fosamax blocks bone resorption

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Summary

• Bone is a complex tissue
• It is constantly being remodeled
• Bones consist of compact and spongy bone, lots of
  blood vessels and nerves
• Functions of bone
• Support and protection
• Movement
• Calcium levels
• Blood cell formation
• Fat storage