Histological study of age related changes in the non-gustatory portion of the tongue in male albino rats

ABSTRACT

Twenty male albino rats were utilized in this study to investigate the histological and ultrastructural changes that occur during morphogenesis of the filiform papillae in the rat. The animals were divided into five groups [four animals each] according to their age. Group A [18-19 day of gestation], group B [0 day - old] group C [2 week old], group D [5-7 months] and group E [18-24 months]. The animals were anaesthetized using ether inhalation, their tongue were removed immediately and processed for light and electron microscope examination. The dorsal surface of the tongue of the prenatal group is covered with the rudiments of the filiform papillae; they were rounded elevation covered by 4-5 layers of epithelial cells with no evidence of keratinization. Scanty collagen fibers appeared in between the lingual muscles. In the 0 day old rat, the filiform papillae were rounded, however a keratinization layer was clearly visible on the tip of each filiform papillae. The distributions of collagen fibers were few in between the lingual muscles and below the mucosa of dorsal surface. In the 2 weeks old rats the filiform papillae on the anterior part of the tongue were conical with pointed tips and covered by a thick keratin layers. Its epithelium was differentiating into anterior and posterior cells columns. The anterior cell column was formed of several layers of flattened epithelial cells. Their cytoplasm were fined with many keratohyaline granules of different size and shapes and few tonofilaments. The cells of the posterior column were elongated with oval nuclei. The cells in this layer were fined with large number of tonofibrils in both the deep and the shallow intermediate layers. Some collagen fibers were increased in between the lingual muscle fibers and in the lamina propria and connective tissue core of the papillae. In the adult group the filiform papillae on the anterior part of the tongue were compactly distributed. They were long, slender and covered by a thick keratin layer. Its epithelium was differentiated into anterior cell column and the posterior cell columns of the filiform papillae and interpapillary cell columns contained keratohyaline granules. Many collagen fibers were increased between the lingual muscle fibers and in connective tissues underlying the papillae. In the senile animals the filiform papillae were less distributed on the dorsal surface of the tongue. They were conical in shape with pointed tips. Their epithelium differentiated into anterior cell columns of filiform papillae fined with many keratohyaline granules and posterior cell columns fined with tonofibrils. The interpapillary cell columns appeared wide and their superficial cells were fined with many keratohyaline granules of different sizes and shapes. Extensive distribution of the collagen fibers in the lamina propria and in the connective tissue core of the papillae. These results indicate that, in rat the morphgenesis of filiform papillae was advanced in parallel with keratinization of the lingual epithelium from the stage just before birth to a stage a few weeks after birth. In senile group the collagen fibers were increased in lamina propria and connective tissue of filiform papillae. These changes affect the distribution and function of these papillae