Early development of nutrient vessels
In the 5th week after conception, the human skeleton is blastemal in structure, consisting of mesenchyme cells in a tissue fluid matrix. In the 7th week, the skeleton of the human embryo is cartilaginous, the long bones consisting of a shaft, enlarged at both ends into the epiphyses of the embryonic bone. Surrounding the shaft of the cartilage model is a vascular perichondrium made up of inner osteogenic and outer fibrous zones (Fig. 4.1). At the beginning of the 8th week (3.5 cm CR length) the centre of the shaft shows chondrocyte hypertrophy, immediately followed by the laying down of a cylindrical primary lamella of bone (Lovén 1863) (Figs 4.2, 4.3). The lamella of Lovén is the first deposit of bone tissue to appear in tubular bones. It is on the primary lamella that a perichondrial collar of bone trabeculae (Ranvier 1875) is then laid down (Figs 4.4, 4.5, overleaf).
KeywordsBone Trabecula Growth Zone Original Magnification Growth Cartilage Nutrient Vessel
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