Observations on the ultrastructure of the ectodermal component during odontogenesis inHelostoma temmincki

摘要

AbstractThe role played by the ectodermal component during lower vertebrate tooth development has been a subject of much speculation. In order to provide new information on this matter the cytostructural changes occuring in the ectodermal part of the tooth buds of a small fresh water fishHelostoma temminckiwere investigated.The cells of the two epithelial layers which form the ectodermal cap of the tooth bud showed little sign of specialization during the early phase of tooth formation. There was no evidence of the synthesis and secretion of enamel matrix. With the onset of the calcification of the dentin specializations indicating an absorptive activity were observed in the cells of the outer epithelial layer. These changes consisted of an elaborate system of canalicular spaces and coated vesicles. Concurrently the cells of the inner layer accumulated large amounts of iron in the form of ferritin particles. The iron was subsequently deposited over the outer layer of the dentin imparting a reddish‐brown coloration to the teeth.The ultrastructural specialization of the ectodermal component during tooth development are suggestive of transport functions similar to those which are thought to occur in post‐secretory enamel organs during the maturation of ena