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Photograph of a section of a foetal hand showing ossification sites at the centre of the metacarpals & phalanges (speckled areas). Human bones are preformed in cartilage (clear areas), forming a soft tissue model, which is later converted into hard osseous tissue. Osteogenesis begins, usually, in a central position (as here) & spreads throughout the skeleton, transforming the cartilage to bone. This process begins during embryonic life & continues through the growing period of the child.
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