Methacrylate-embedded E20 embryo in the coronal plane (posterior)
Figure 122. This is a slice from the same specimen in Figure 122 cut farther back into the olfactory peduncle where the accessory olfactory bulb occupies the dorsal surface. The AOB output neurons—much smaller than mitral cells—form a well-defined clump sandwiched between the external and internal plexiform layers. The granule cells of the AOB are settling deep to the internal plexiform layer. In the MOB, the layers are nearly the same as in Figure 121. The granule cell layer is indistinguishable from the olfactory SVZ, that is just outside the columnar cells of the olfactory NEP. The pars externa of the anterior olfactory nucleus may be on either side of the AOB, but the rest of the nucleus is farther back in the peduncle and not in this slice. Just as in Figure 121, the mitral cell layer forms a continuous U-shaped layer beneath the AOB part of the slice. In this specimen, the right olfactory bulb is missing because it was cut off during dissection.