Olfaction is the sensory process that in response to chemical stimuli gives rise to those sensations called odors. The primary olfactory receptive area is that region of the nose subserved by the olfactory nerve. Although the chemoreceptive endings and neural projections of the olfactory nerve are basic to the sensing of odors, other cranial nerves are also involved, namely, the trigeminal, glossopharyngeal, and vagus. These additional cranial nerves possess at least some chemoreceptive endings which line the respiratory tract at different levels (nose, pharynx, larynx) and together define the accessory areas of olfaction. These accessory areas, especially that of the trigeminal nerve, give rise to the pungent or irritating quality often experienced as part of an odor sensation. It is not yet certain, however, that these nociceptive-like qualities are the only contribution that the accessory areas give to the total odor sensation. Nonetheless, the existence of accessory olfactory areas in addition to the primary area requires caution in testing and evaluating olfactory function since, for instance, an odorant might be detected through the trigeminal input even though the olfactory receptors are unresponsive.
KeywordsReceptor Cell Olfactory Nerve Accessory Area Olfactory Mucosa Ethyl Mercaptan
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