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Longitudinal Growth

- See:
      - Limb Development
      - Pediatric Bone Circulation
      - Salter Harris
      - Epiphyseal Physis:

- Discussion:
    - longitudinal growth depends on both proliferation and hypertrophy of chondrocytes in the growth plate;
    - longitudinal growth of bone is complicated by physical limitations of bone tissue and by need to maintain function during growth process;
    - appositional growth:
          - application of new bone on surface of existing bone;
          - requires of haversian systems to maintain viability of the osteocytes;
    - longitudinal growth is complicated by presence of articular cartilage at each end;
          - this cartilage must retain its specific shape and strength to permit proper joint function during growth;
    - small bone growth (cuboid);
          - accomplished through cell division & growth of deeper layers of articular cartilage, which is subsequently replaced by bone on its 
                 deep surface;
          - articular cartilage is thus constantly being pushed forward by newly formed cartilage, which in turn is replaced by bone;
    - long bone growth:
          - requires relatively rapid growth rate;
          - epiphyseal plate permits rapid growth;
                  - exchanging of cartilage for bone is called enchondral ossification;
                  - deeper layers of cartilage cells multiply & enlarge, pushing epiphysis & its overlying articular cartilage away from metaphysis & 
                  - multiplication & growth of epiphyseal cartilage cells tend to thicken growth plate, but as rapidly as new cartilage cells are 
                           formed at base of the plate, cartilage cells are destroyed and replaced by bone on the metaphyseal side of the plate;
                           - plate, therefore, maintains a relatively constant thickness during growing period

Quantitation of chondrocyte performance in growth-plate cartilage during longitudinal bone growth.

Earliest evidence of cartilage and bone development in embryonic life.

Longitudinal growth and growth-plate activity in the lower extremity.