Histogenesis Study of Fetal Cerebellum in Gezel sheep

The purpose of this study is to determine the differentiation time of cerebellum tissue during fetal life. This study is a descriptive observation of 100 fetuses of pregnant sheep uterus that were chosen randomly. After fixation, morphological measurement and preparing histological sections, the samples were stained by H&E and were examined under a light microscope. According to microscopic observations of 40th day of gestation, cerebellum tissue had not yet differentiated. Therefore, at this stage, the appearance of cerebellum was like an overlying mass of neuroepithelial cells in metencephalon area of neural tube. At the 50th day of gestation, the initial form of the cerebellum was separable due to the placement of migrating cells in layers and creating initial wrinkle under the pia mater. At the 70th day, great number of wrinkles could be seen on long strips in a way that primary wrinkle was underneath the secondary wrinkle. At the 80th day of gestation, Purkinje cells were observed between granular and molecular layers. At the 90th day of gestation, cerebellum tissue had primary, secondary, and tertiary wrinkles. At the 120th day, the whole tissue structure of cerebellum, in the last month of pregnancy, was seen as a mature form in a way that in the last three months there were no significant changes. This can be concluded that the differentiation of cerebellum tissue from the mass of migrating cells of neural tube starts after the sixth week and the whole cerebellum tissue structure appears in fetal life and a month before birth.