Morphological changes in ventricular germinal zone and neocortex of the cerebral hemispheres in human fetuses and newborns on weeks 22–40 of prenatal development

Abstract

In this study, we investigated the morphology of the ventricular germinal zone and neocortex of the cerebral hemispheres in the projection field no. 4 of the motor area in human fetuses in dynamics from week 22 to 40 of fetal development. Morphological study allowed us to clarify the following patterns of prenatal ontogeny of the human CNS. On weeks 22-27, an intensive formation of the main sulci of the first order, differentiating the brain into lobes, is observed. By weeks 28-32, the formation of all sulci of the first order is completed; and on weeks 33-37, additional sulci characteristic of an individual are formed. The spurt of gyrification of the cortex (weeks 22-27) practically coincides with the completion of neuronal differentiation and formation of the motor neocortex. The structure of the latter is characterized by a clear stratification of cytoarchitectonic layers and modular organization of neurons with their vertical orientation in cell columns (weeks 25-27). In subsequent weeks of prenatal development until birth, no significant changes in the topography and structure of the neocortex are observed. Structural rearrangement of the ventricular germinal zone on weeks 22-40 of prenatal development consists in its gradual reduction and is completed on weeks 37-40. The criteria of physiological reduction of this area are the zonal location of glioblasts and a progressive decrease in its thickness on weeks 33-37 of prenatal development.