Palis S. Peculiarities of morphogenesis and structure of the mandible during prenatal period of human ontogenesis

With the purpose to determine peculiarities of development and spatial-temporal dynamics of formation of the mandible at the early period of ontogenesis, to find out correlation regularities of the constitutional and sexual-age changeability of the mandible in human fetuses, the specimens of 30 embryos, 30 pre-fetuses and 60 human fetuses were investigated. For the first time, by means of a set of methods of morphological examination the peculiarities of dynamics of spatial-temporal transformations of the mandible and its morphological changes during the fetal period of prenatal human ontogenesis are clarified. The study concerning morphogenesis and structure of the mandible during intrauterine period of human development is expanded and added: the origin, time of anlage and peculiarities of chronologic regularity of the human mandible morphogenesis are stipulated due to application of a set of classical and up-to-date methods of morphological examination and medical diagnostic visualization. For the first time, the regularities of spatial-temporal dynamics of the mandible formation during the early period of human ontogenesis are determined. For the first time, the constitutional and sexual-age changeability of the mandible is found out on the basis of detection of constitutional types of human fetuses and their correlation analysis by the sex and term of the prenatal development. For the first time, critical periods of development and formation of the human mandible are determined, three-dimensional reconstructions and mathematical models of the human mandible are designed. On the basis of the obtained digital indices of the main morphometric parameters of the human mandible in the dynamics of pre-fetal period of the intrauterine development, we have found out critical periods of their morphogenesis and deduced mathematic functions describing normal course of the mandible organogenesis, which can be used for diagnostic algorithms of the norm during prenatal diagnostics and monitoring of the fetal condition. Therefore, the 9-10th weeks of the intrauterine development are critical for the development of human mandible, since during this time intensive growth processes occur manifested in radical changes in the size of the organ, and it can cause different structural variants and possible congenital defects of the mandible and dental-facial system on the whole. The study of interrelations between age, constitutional type coefficient and morphometric parameters of human fetuses of both sexes has enabled to find out the regularities of individual anatomical variability, sexual-age and constitutional features of the mandible structure during the fetal period of human ontogenesis. The distance between the articular processes of the mandible in human fetuses of both sexes is found to increase evenly, although in dolichomorphic female objects the rates of growth of this index increase intensively since the 6th month of the intrauterine development. The angle of the mandible of the human fetuses decreases during the prenatal development except brachimorphic female objects. On the contrary, their morphometric parameter increases since the 4th month of development and till birth. The angle of the mandible possesses the tendency to increase in all the examined fetuses except brachimorphic objects whose parameter decreases during the prenatal development. The mandible height in brachimorphic objects of human fetuses of both sexes decreases, while in the rest of fetuses – increases. The mandible body length and maximal mandible length in all the examined human fetuses decrease but in female fetuses of all the constitutional types this parameter begins to grow intensively since the 6th month and till the end of the prenatal period of ontogenesis. Sagittal length and thickness of the mandible in fetuses of both sexes of brachimorphic constitutional type have the tendency to decrease, and in dolichomorphic female objects it increases linearly since the 6th month of development. The volume and area of the mandible surface in human fetuses prevail in female fetuses of brachimorphic constitutional type, and the smallest values of these parameters are found in male fetuses of dolichomorphic constitutional type at the end of the fetal period and in female fetuses of brachimorphic constitutional type in the 6-7th months of the intrauterine development. The 6-7th months of the intrauterine development are a critical period of mandible morphogenesis during the fetal period of human development sometimes including intensive changes of growth rate of the organ depending on sex and constitutional type