Methacrylate-embedded E21 embryo in the horizontal plane (intermediate)
Figure 132 is an intermediate slice through the MOB in the same specimen as Figure 131 that cuts the olfactory recess—note the cells in the ventricular lumen that must have ruptured from the olfactory NEP or SVZ. The migratory stream of mitral cells is prominent on the lateral side of the bulb flowing out of the lateral olfactory tract as it spreads into the internal plexiform layer. Fewer spindle-shaped cells are in the medial internal plexiform layer. The base of the mitral cell layer is easily distinguished from the internal plexiform layer because fewer cells are entering from below. The anterior olfactory nucleus and the primary olfactory cortex are more clearly defined and separate from the MOB than in the E20 embryos.