Histological study of the taste buds of the circumvallate papilla in the tongue of male albino rat in different ages

Twenty male albino rats were utilized in this study to investigate the histological, and ultrastructural modification in the circumvallate papillae of male albino rat with special attention to the development of taste bud during prenatal, postnatal development and aging. The animals were divided into five groups [four animals each] according to the their age Group A prenatal animals [18-19 day of gestation] group B [0 day old] group C [2 week old, group D [adult 5-7 months] and group E senile [18-24 months]. The animals were anaesthetized using ether inhalation, their tongues were dissected immediately and processed for light and electron microscope examinations. The circumvallate papilla of the prenatal group was dome shaped elevation covered with non keratinized stratified squamous epithelium and surrounded by a closed furrow from both sides, No taste buds were observed. In 0 day old rats the circumvallate papilla was surrounded by a partially obliterated furrow and the papillary wall was lined by immature taste buds, formed of few clusters of dark and light cells without taste pore. Their nuclei were found at the apical and basal poles of the buds, also unmyelinated nerve fibers were detected between these cells. By the age of two weeks the circumvallate papilla was surrounded by an opened furrow which lined by immature taste bud without taste pore. Many light cells and some dark cells were noticed on the apical and basal pole of the buds. In addition unmyelinated nerve fibers were detected between taste cells. In adult group, the circumvallate papilla was surrounded by an opened furrow and its wall was lined by many mature taste buds with taste pores. Each task bud was formed of elongated cells, that converge at the taste pore, their nuclei occupied the basal half of the bud. The taste bud was formed of dark, light, intermediate and basal cells. The dark cells were small irregular in their outline with electron dense cytoplasm and nuclei. They extended cytoplasmic processes that separated and surrounded the other taste cells and intragemmal nerve fibers. The apical part of these cells contained dense secretory granules. The light cells were larger than dark cells and contained large smooth outline oval. They were characterized by electron lucent vesiculated cytoplasm. The intermediate cells were less common type of cells found in the adult rat taste buds. They were found to share characteristic of both light and dark cells and their cytoplasm were moderate in electron density between light and dark cells. In senile group, the circumvallate taste buds were formed from few elongated cells that converge at the taste pore and their nuclei occupied the basal half of the bud. Each taste bud was formed of dark and light cells. The dark cells were the commonest cell type and they were small irregular in outline with electron dense cytoplasm and nuclei. Few light cells with electron lucent cytoplasm and large oval nuclei Unmyelinated nerve fibers were observed between these cells. It become clear that the peripheral gustatory system was maintained histologically over a wide age range. Thus the change in the taste acuity reported in old age may be due to histological or biochemical changes in the taste cells

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

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