الفهرس 
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Abstract
The tongue is the responsible organ for speech and detecting foreign bodies in the oral cavity. It has a role in mastication and helps in swallowing the food.
This study was carried out to investigate the histological and scanning electron microscopic characters of the middle part of anterior two thirds of the rat tongue after birth during postnatal and aging periods.
The experimental animals: 20 white albino rats, they were divided into: young age: (1,14,30 days), middle age (3 months) and old age ( 2 years).
Tongue specimens were taken and processed to be examined by Light and Scanning electron microscopy.
The present results revealed during postnatal development (1 day to 3 months):
The histological findings: There was an increase in thickness of epithelium of dorsal and ventral surfaces, increase in thickness of keratin layer, increase in size of filiform and fungiform papillae, increase in size of taste bud in fungiform papillae and increase in size of muscle fibers.
Also Scanning electron microscope findings revealed an increase in size of filiform papillae, increase in size of fungiform papillae, increased depth of their circular furrows and increase in numbers of micropits and microridges on the surface epithelium of filiform and fungiform papillae.
Microvilli projecting from taste pores could be seen at adult age.
Growth factors and hormones might be the responsible factors for postnatal development of the tongue. Differences in environment, diet might modify the morphology and structure of the tongue in postnatal
developmental periods.
Our light microscopic results as a result of aging of the rat tongue revealed a decrease in thickness of epithelium of dorsal and ventral surfaces, decrease in thickness of keratin layer, increase in size of filiform and fungiform papillae, decrease in size of taste bud in fungiform papillae and decrease in size of muscle fibers.
Also Scanning electron microscope revealed an increase in the size of filiform papillae and fungiform papillae, increase in the depth of their circular furrows, decrease in numbers of micropits and microridges on the surface epithelium of filiform and fungiform papillae. Well defined microvilli projecting from taste pores. Taste pores couldn’t be identified at some fungiform papillae confirmed absence of presumed underlying taste buds.
Apoptosis (programmed cell death) or accumulation of oxygen free radicals inside the cells might be the major contributors of aging. Damage in DNA, proteins, membranes, and organelles, as well as the accumulation of high molecular weight insoluble aggregates were theories of aging process. Environmental, genetic, metabolic, disease and behavioral factors might modify the morphology of the tongue.
Albino rats could be a useful experimental model of studying postnatal development, aging changes of tongue and of the relationship between age and oral diseases as the changes were similar to those in human lingual epithelium might explain the impairment of taste and difficulties of swallowing in elderly persons.
Further researches are recommended to explain mechanisms and theories of these changes of the tongue during development and aging periods.