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Abstract layer and auter loose one. Collagenous and elastic fibers ~he presen~ s~udy has revealed that the paramesonephric ducts are the primordial s t r uc t ur-e s irom which ~he u~erus lped. They begin to develop in the 35 days old embryo as )w epi~helial invaginations at the cranial poles of -::he sphr o t . In 38 days old embrvo, ~heir grow~h level has led -;:0 abou~ -::he biginning of the caudal third of ”the -phr oa . During the 2nd developmentalmorrt n , the growth of ::he lad extended beyond the mesonephroi and they beEin to f us e 19 the uterine body and the uterovaginal primordium which lue its caudal growth to reach the urogenital sinus by -::he ,ay. Uterine differentiation began its initiation during the veloomental month. At ~his period ~he uterine wall of -;:he nd horns was comprised of; an epithelial lining of densely cells resting on thin, even basal lamina and a thelial layer of undifferentiated mesenchyme. By the onset 4-::h d,::.veloomental mon~h. the uterine epithelium tended pseudostra~ified columnar type. The subepi-::helial hymal layer was made up of two distinct layers 3n inner n~irelv absen~. By -::he day 110, the outer mesenchymal layer ted some differen~iated’ fibroblasts and by the end of this small bundles of collagenous fibers were encoun~ered. 85 Through the 5th month, the wall of the uterine horn and body exhibited a circular band of developing myoblasts between the inner and outer mesenchymal layer. Accordingly. the uterine wall appeared to be formed of inner mucosa. middle muscular layer and an outer serosa. By the end of the 5th month. the caruncles initiated their development as shallow epithelial invaginations penetrating thG underlying stroma. Through the 6th month, -:he uterine lumen irregularity was gradually increased due progressive epithelial invaginations, forming 3 or 4 epithelial clefts. consequently the uterine mucosa appeared to be organized of raised circumscribed areas separated by deep clefts forming nodular and internodular areas. At the last week of the 6th month. the inter nodular clefts showed basal branches extending in a direction parallel to the summit of the nodular area. The propria submucosa was still of primative mesenchymal nature. The myometrium was slightly increased in thickness. from the 7th to the 10th month, the polymorphic uterine nodules were graduall:! increased in size and protruded more into the lumen. The myometrium showed progressive increase in thickeness being formed mainly of circularly arranged smooth muscle fibers and an outer. comparatively thin, logitudinal layer. was The perimetrium differentiated into loose connective tissue layer with an outer mesothelium. By the end of the 10th developmental month. the uterine glands primordia were firstly observed as short epithelial downgrowths from the bases and sides of the intercaruncular areas into the underlying stroma. The fetal myometrium and perimetrium 86 showed ~he normal developmental growth related to gradual increase in thickeness as a resul~ of the proliferation of their components. Cervix : The cervix was firstly recognized in ~he caudal fused part of ~he paramesonephric ducts a~ about the middle of the 3rd developmental month. At this age, the cervical mucosa was slightly folded and the cervical wall consisted of lamina epithelialis surrounded by exclusively cellular mesenchymal layer. Within the latter layer, small isolated bundles of smooth muscles were noticed dividing it into an inner layer representing the future propria-submucosa and an outer one representing the serosa. Through the 4th month, the folding process was continued and the cervical epithelium showed some areas of pseudostratification. The epithelial cytoplasm showed considerable amount of glycogen granules and marked reactivity to PAS. By the begining of the 5th month, the cervical mucosa appeared organized of large, number of short, comparatively wide folds. The propria-submucosa showed ~he presence of several epithelial sinuses which were encountered throughout the succeeding developmental stages. The muscular layer was slightly increased in thickness and by the end of the 5th month, i~ was organized into an inner circular and thin ou~er longitudinal layer. The inner circular layer has been given off cental or bilateral ramifica~ions into the cores of ~he major cervical folds. At the begining of the 6th month, the cervical 87 mucosa was ~hrown into large primary folds superficially divided were evident along the entire length of the cervix. At the into smaller ones. By the end of this month. two annular rings begining of the 7th month, folding and branching of the cervical muscosa wa~ advanced with a substantial reduc~ion in the width of the lumen. During the 8th months, the large primary cervical folds were equipped with secondary and tertiary folds and goblet cells were noticed among the epithelial lining. Through the 10th month, the elaborately folded cervical mucosa had reached its full expression. The cervical epithelium became mostly simple columnar or cuboidal by the end of this month. The propria-submucosa showed a gradual relative increase in the number of fibroblasts collagenous and elastic fibres and by the end of the 10th month it was looking like loose connective tissue. The muscular layer has been extensively thickened and became composed of 4 or 5 inner circular and one outer longitudinal layers of smooth muscle cells. 88 |