Methacrylate-embedded E18 embryo (lateral sagittal)
Figure 83. This lateral sagittal slice, from the same specimen in Figure 82, tangentially cuts through the olfactory bulb NEP and SVZ. The NEP and SVZ of the anterolateral and posteromedial basal ganglionic fuse, forming a bridge over the basal telencephalic NEP and SVZ in the large lumen of the lateral ventricle. The AOB and MOB can be easily distinguished in the expanding olfactory bulb. The AOB layering is like that in Figure 82, except the beginnings of a granule cell layer can be identified at the deep border of the internal plexiform layer. The mitral cell layer in the MOB is more indistinct (a tangential cut) and consists of clusters of cells with densely-staining cytoplasm adjacent to the cell-sparse external plexiform layer. Compared to the medial slice in Figure 82, more spindle-shaped cells appear to be migrating into the ventral MOB near the pial surface in the region of the postulated anterior olfactory nucleus. Coalesced fiber bundles of the olfactory nerve surround the bulb and form a thick ventral bundle. Individual bundles of the olfactory nerve are growing in between the undulations of the olfactory epithelium in the superior nasal cavity.