Vertebrates
Humans have about 40 million olfactory receptors that detect up to 10,000 different odors. In vertebrates, ORNs are bipolar neurons with dendrites facing the interior space of the nasal cavity and an axon that passes through the cribiform plate then travels along the olfactory nerve to the olfactory bulb. The ORNs are located in the olfactory epithelium in the nasal cavity. The cell bodies of the ORNs are distributed among all three of the stratified layers of the olfactory epithelium.
Read more about this topic: Olfactory Receptor Neuron