Methacrylate-embedded E20 embryo in the horizontal-coronal plane (posterior)
Figure 120. This is a posterior and ventral slice through olfactory bulb in the same E20 specimen shown in Figure 119. In this slice, the AOB forms a more prominent hump with a fairly large accumulation of medium-sized output neurons. The AOB granule cells are tentatively distinguished beneath the AOB part of the internal plexiform layer. Some displaced output neurons reside in the external plexiform layer, and whorls of vomeronasal nerve fibers are in the outermost layer. In the MOB, the cells shed into the olfactory recess are prominent, surrounded by the NEP, SVZ, and presumptive granule cell layer. As in Figure 119, spindle-shaped cells dominate in the internal plexiform layer, most of which will end up in or superficial to the mitral cell layer. The olfactory nerve forms large medial and lateral clumps on the ventral surface of the bulb. The most medial fibers may be part of the vomeronasal nerve heading toward the AOB.