Abstract

We examined sixty-three human embryos ranged from three weeks to eight weeks of fertilization age and 117 human fetuses from eleven weeks to fourty weeks of gestational age. Anatomical structure of developing tongue could be classified into eight developmental stages. The first is the sgage of mesial swelling of tongue primordium in the fertilization age of 28~40 days (Streeter stage 13~16), the second is the stage of lateral swelling of tongue primordium in the fertilization age of 41~46 days (Streeter stage 17~18), the third is the sgage of vertical positioning of tongue in the fertilization age of 47~53 days (Streeter stage 19~21), the fourth is the transitional stage of tongue from vertical position to horizontal position in the fertilization age of 54~56 days (Streeter stage 22~23), the fifth is the stage horizontal positioning of tongue in the gestational age of 11 weeks, the sixth is the stage of protrusion of tongue in the gestational age of 12 weeks, the seventh is the stage of maturation of tongue muscle in the gestational age of 7-10 months. The development of tongue papilla characteristically progresses into three stages. The first stage is the epithelial ingrowth for the crypt formation, the second stage is the anatomical formation of vallate, fungiform and filiform papillae, and the third stage is the differentiation of taste buds in the vallate and fungiform papillae or the formation of thick spike-like keratinization at the tip of filiform papilla. We observed that the tongue primordium mainly derived from occipital myotome developed more repidly than other oro-facial structures, so it transitionally occuied the spaces of the pharynx and the posterior nasal cavity, and directly affected the formation of palate and the growth of maxilla and mandible. Whereas the tongue papilla development showed continuous developmental sequences during the fetal period.

• Keywords: Fetus;Tongeu;Development;Papilla;Taste Bud;