Skeletal units of the human embryonic mandible.

The development of the mandible was traced on serial sections of 20 human embryos aged 5-8 weeks (developmental stages 13-23). Special consideration was given to the differentiation of skeletal units proposed by Sperber. The first skeletal units, namely the mandibular body, the alveolar unit and the condylar unit, may be distinguished in the 7(th) week. The primordia of all units are identified by the end of the embryonic period (8 weeks).