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Methacrylate-embedded E16 embryo (posterior coronal)

Figure 56.  This is a slice from the same specimen in Figure 55 cut farther back into the olfactory peduncle (left side) and the lumen of the olfactory recess (right side).  Similar laminar features seen in Figure 55 are in the MOB in this slice: the sharp decline in cell density between the olfactory nerve layer and the very thin external plexiform layer, migrating mitral cells in the internal plexiform layer.  The AOB output neurons are tentatively identified on the left side, dorsal to the MOB; the slice cuts posterior to the AOB on the right.  The MOB primordium on the right occupies the part of the olfactory peduncle that is contacted by the olfactory nerve; straight arrows indicate radially migrating cells, while the curved arrow traces the migration route of at least some mitral cells from the basal telencephalic NEP that percolate through cells that may be settling in the primary olfactory cortex.  The olfactory epithelium lines the superior part of the nasal cavity and gradually thins into the nasal mucosa.  Jacobson’s organ is a medial hook in the inferior nasal cavity.  Fascicles of the vomeronasal nerve are on either side of the nasal septum.