Neuropathological processes of the olfactory system in neurodegenerative diseases. Gross anatomy of the nose, the olfactory nerve, and the olfactory bulb, and cellular and molecular neuropathology. (OSN: olfactory sensory neurons, DA: dopaminergic, OT: olfactory tract, PC: piriform cortex, AMG: cortical nucleus of the amygdala, EC: entorhinal cortex, OFC: orbitofrontal cortex.)