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48 mm CRL
Telencephalon
Surface of the cerebral hemispheres.
Because brain extraction was not performed, description of the brain surface is based on serial sections.
On the superior (dorsal) surface, the interhemispheric fissure (fissura interhemispherica) is visible, traversing the entire dorsal surface of the brain and separating the hemispheres.
The primary calcarine sulcus (sulcus calcarinus) and parietooccipital sulcus (sulcus parietooccipitalis) emerge as early as the 12th gestational week. These primary sulci appeared as folds in the entire medial hemispheric wall. This arrangement of sulci on the medial brain surface was observed until 17 gw (Godovalova et al., 2024).
Transient zones, histogenesis of the neocortex.
At the 12th week of gestational development, the formation of transient zones continues. At this time, a clear characteristic structure can already be distinguished in the lateral and medial hemispheric walls, organized into five transient zones (Fig. 1):
Ventricular zone;
Subventricular zone. During this period, the division of the subventricular zone into two subzones is already visible in the lateral wall.
Intermediate zone;
Cortical plate;
Marginal zone
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)
According to our data, the average GE width at the level of the interventricular foramina at the 11th-12th gestational week (CRL 48 mm) increases to 1.7 mm and remains approximately at this level until the 17th week. GE volume - 3.94 mm3 (Proshchina et al., 2024).
Histogenesis of the subpallial structure
Neostriatum
Total volume of neostriatum 3,06 mm3
Volume of caudate nucleus 0,99 mm3
Volume of putamen 2,07 mm3
48 mm CRL
Telencephalon
Surface of the cerebral hemispheres.
Because brain extraction was not performed, description of the brain surface is based on serial sections.
On the superior (dorsal) surface, the interhemispheric fissure (fissura interhemispherica) is visible, traversing the entire dorsal surface of the brain and separating the hemispheres.
The primary calcarine sulcus (sulcus calcarinus) and parietooccipital sulcus (sulcus parietooccipitalis) emerge as early as the 12th gestational week. These primary sulci appeared as folds in the entire medial hemispheric wall. This arrangement of sulci on the medial brain surface was observed until 17 gw (Godovalova et al., 2024).
Transient zones, histogenesis of the neocortex.
At the 12th week of gestational development, the formation of transient zones continues. At this time, a clear characteristic structure can already be distinguished in the lateral and medial hemispheric walls, organized into five transient zones (Fig. 1):
Ventricular zone;
Subventricular zone. During this period, the division of the subventricular zone into two subzones is already visible in the lateral wall.
Intermediate zone;
Cortical plate;
Marginal zone
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)
According to our data, the average GE width at the level of the interventricular foramina at the 11th-12th gestational week (CRL 48 mm) increases to 1.7 mm and remains approximately at this level until the 17th week. GE volume - 3.94 mm3 (Proshchina et al., 2024).
Histogenesis of the subpallial structure
Neostriatum
Total volume of neostriatum 3,06 mm3
Volume of caudate nucleus 0,99 mm3
Volume of putamen 2,07 mm3