The olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. The specialize olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity. The olfactory nerves do not form two trunks like the remaining cranial nerves, but consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the Cribriform plate of the Ethmoid bone; a sieve-like structure.