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Transient zones of the hemispheric wall, histogenesis of the neocortex.
At Carnegie stage 20 (the beginning of the 10th GW), three clearly distinguishable zones were visible in the lateral wall of the hemispheres.The thick-cell ventricular zone (zona ventricularis, matrix germinalis, VZ) was at the border with the ventricles, followed by a sparser cellular zone prelamina (PP}.The third zone of the neuromesenchyme contained few cell nuclei. At this stage, only two zones were identified in the medial wall: the proliferative VZ and the neuromesenchyme.
At Carnegie stage 20 (the beginning of the 10th GW), three clearly distinguishable zones were visible in the lateral wall of the hemispheres.The thick-cell ventricular zone (zona ventricularis, matrix germinalis, VZ) was at the border with the ventricles, followed by a sparser cellular zone prelamina (PP}.The third zone of the neuromesenchyme contained few cell nuclei. At this stage, only two zones were identified in the medial wall: the proliferative VZ and the neuromesenchyme.
Already at the 21st stage of Carnegie, three zones were revealed in the dorsomedial hemispheric wall (Figure 1): the VZ, PP, and the neuromesenchyme. In the lateral wall, a clear characteristic structure, organized into five tranzional zones (Figure 1) was revealed: the part of the hemispheric wall, bordering the ventricular cavity, formed the VZ, in which the cell bodies were densely located. Above the VZ,there was a sparser SVZ. Next, a cell-poor IZwas revealed. The cytoarchitectonics of the future cortex at this time was quite simple and consisted of two distinct cell zones. Above the IZ, the undifferentiated CP was detected, and above it, the light marginal layer (MZ) was clearly revealed. At this stage of development, the CP was . less than the VZ . The medial wall of the hemisphere was narrower than the lateral one (for more information see Proshchina et al., 2024).
Ganglionic eminence (GE, eminentia ventricularis lateralis)
In humans, the medial GE begins to form at the 14th Carnegie stage (CRL 5-7 mm). At the 15th stage, a lateral GE begins to form, but it is not expressed macroscopically. By the 18th-20th Carnegie stages (CRL 13-22 mm), the length of GE is ~ 1.0 mm, height — 0.4 mm, and width — 0.3 mm (Proshchina et al., 2024).
Histogenesis of the subpallial structure
Neostriatum
Total volume of neostriatum
Volume of caudate nucleus
Volume of putamen
Ganglionic eminence (GE, eminentia ventricularis lateralis)
In humans, the medial GE begins to form at the 14th Carnegie stage (CRL 5-7 mm). At the 15th stage, a lateral GE begins to form, but it is not expressed macroscopically. By the 18th-20th Carnegie stages (CRL 13-22 mm), the length of GE is ~ 1.0 mm, height — 0.4 mm, and width — 0.3 mm (Proshchina et al., 2024).
Histogenesis of the subpallial structure
Neostriatum
Total volume of neostriatum
Volume of caudate nucleus
Volume of putamen