Human tooth development the formation of odontoblasts continue from the tips of the cusps, the odontoblasts secrete a substance, an organic matrix, into their immediate surrounding. The organic matrix contains the material needed for dentin formation. As odontoblasts deposit organic matrix termed predentin, they migrate toward the center of the dental papilla. Thus, unlike enamel, dentin starts forming in the surface closest to the outside of the tooth and proceeds inward. Cytoplasmic extensions are left behind as the odontoblasts move inward. The unique, tubular microscopic appearance of dentin is a result of the formation of dentin around these extensions. After dentin formation begins,
Sociology of human consciousness presumed evolutionary advantages of human reflectivity must be qualified or viewed as conditional. In sum, recent research, building on the work of George Herbert Mead, suggests that a sociological and social psychological perspective can be a point of departure with which to define and analyze certain forms of human consciousness, or more precisely, one class of consciousness phenomena, namely verbalized reflectivity: monitoring, discussing, judging and re-orienting and re-organizing self; representing and analyzing what characterizes the self, what self perceives, judges, could do, should do (or should not do)). The "hard problem" of consciousness can be approached fruitfully by beginning with