الفهرس 
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Abstract
Introduction : One hundred and thirty eight albino rats were used in this study. They were divided into three groups; the first group (control) includes six adult male and six adult female albino rats, used for evaluation of the postnatal development and to compare the effect of castration with or without androgen treatment. The second group formed of one hundred and eight albino rat of both sexes, their ages started from day of birth up to sixteen weeks. This group used to follow the postnatal development and determine how sex differences arise during postnatal development of rat SMG. The third group comprised of eighteen male rats used to study the effect of castration with or without androgen treatment. At birth, the SMG was not completely developed. Its development was completed at the twelfth week of postnatal development. During the first six weeks of postnatal life, the structure of the gland was similar in both sexes. Sexual dimorphism was first detected at the age of the sixth week when GCTs appeared. Their number increased gradually with reduction in the number of SD. The size and number of GCTs were more in male than in female. The maturation of the GCT was complete at the 12th week. Regarding the morphometric analysis in the present study, sexual dimorphism was detected in the area % of GCT, height of its cells, area % and diameter of the acini. But no sexual dimorphism was detected in the area % and diameter of SD. The area %, height of cells of GCTs and diameter of acini were larger in male than in female. While area % of the acini was larger in female than in male which indicated increase the number of acini in female. The present study yielded evidence of testosterone sensitivity of the submandibular gland in so far castration decreased while testosterone injection increased the weight of the gland. It was found that castration caused hypotrophy of the GCT that appeared small, less convoluted and sparsly distributed within the glandular parenchyma. Conversely, testosterone injection resulted in a considerable increase in the number, size and convolution of these tubules. After castration, the histological structure of the submandibular gland became like that of normal female rats. After testosterone injection, the picture of normal male rats was restored. Regarding the morphometric analysis, it was found that castration decreasaed area percent and height of cells of GCT while testosterone injection restored them. Conclusion : (1) At birth, the submandibular gland is not completely developed in both sexes; it reaches maturity at the 12th week of postnatal development. (2) No sexual dimorphism till the age of puperty which indicate the sensitivity of the gland to sex hormones. (3) Area %, height of GCT and diameter of acini larger in male than in female which indicate sensitivity of GCT and acini to androgen. (4) Castration abolishes sex dimorphism while testosterone injection established it.