102 The Foundations of Health

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102 The Foundations of Health and Disease
Development Growth of the Human Skeleton
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skeleton

• bilateral symmetrical pattern
• segmental axis - allows flexibility
• limbs attached by girdles
• skull

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nature of bone

• strong
• flexible
• tubular structure
• strong
• light
• economical

• large compression forces at articular
• surfaces

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development

• hyaline cartilage model
• some in mesenchyme
• soft tissue model
• undergoes osteogenesis
• primary centre of ossification

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ossification

• begins intra-uterine life - 8 weeks IU
• completed late teens, early 20s
• adaptation to growth
• smaller bones - one ossification
• centre
• estimate age through radiology

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long bones

• ossify from several different centres
• first centre 8 weeks IU life
• primary centre progressive
• ossification towards ends of bone
• ends ossify in separate centres
• secondary centres of ossification

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long bones
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ossification of long bones

• shaft diaphysis primary ossification
• centre
• epiphysis secondary centres for
• ossification
• epiphyseal plate between epiphysis and
• diaphysis
• adaptation to growth
• maturity fusion of diaphysis with epiphysis

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skeletal tissues

• cartilage and bone
• 3 elements
• cells
• intercellular matrix
• system of fibres
• collagen
• elastin
• reticulin

• bone and cartilage
• modified connective tissues solid matrix

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classification of bones

• by appearance
• compact
• spongy, trabecular, cancellous
• by developmental origin
• intramembranous bones of skull
• endochondral long bones
• by region of the bone
• diaphysis
• epiphysis
• metaphysis

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intramembranous ossification
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endochondral ossification
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structure of bone
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compact bone
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how does bone arise?

• endochondral
• intramembranous
• very little difference in process
• tissues of origin

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endochondral

• cartilagenous model
• starts at primary centre of
• ossification
• outside cartilagenous model
• mesenchymal cells
• mesenchymal cells perichondrium
• deep layers of perichondrium
• contain osteogenic precursor cells

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primary centre ossification

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bone growth
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endochonral ossification
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further development

• initially spongy bone laid down
• Haversian systems
• interstitial bone fill in spaces

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compact bone
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bone growth