Ultrastructure of the enamel layer in developing teeth of the shark Carcharhinus menisorrah

摘要: Abstract The first two rows of teeth at the posterior end dental lamina in a 60 cm specimen Carcharhinus menisorrah were uncalcified, but calcification had begun tooth-cap layer tips third-row teeth. Enamel crystals developed within hollow enameline fibrils (tubules) which polymerized beneath basement menbrane underlying ameloblasts. Vesicles containing fine granules present apical cytoplasm ameloblasts tooth buds prior to calcification. Fine granular material accumulated extracellularly between and membrane, also matrix on pulpal side membrane. morphology suggests that secrete precursor for mineralizing fibrils. with their fibrous coatings tightly packed zones. Crystals became indefinitely long equilaterally hexagonal cross section. They aligned parallel bundles interwoven Odontoblast processes myelinated nerve fibres penetrated into cap Giant banding periodicity 14.5 nm occurred partitioning zones mineralization. Their origin nature are uncertain. Conventional collagen connective tissue base tooth, dentine after it began differentiate. mineralized needle-shaped as mammals. shark's is considered be composed tubular enamel probably homologous mammalian enamel, by odontoblast mesodermal origin.