Definition of Olfaction

Olfaction: The sense of smell, part of the chemical sensing system, or the chemosenses. Sensory cells in the nose, mouth, and throat have a role in helping interpret smells and taste flavors. Microscopic molecules released by substances (foods, flowers, etc.) stimulate these sensory cells. Once the cells detect the molecules they send messages to the brain, where the smell is identified.

Olfactory, or smell nerve cells, are stimulated by odors such as the fragrance of a gardenia or the smell of bread baking. These nerve cells are found in small patches of tissue (the olfactory membranes) about the size of a postage stamp that are located in a pair of clefts just under the bridge of the nose high inside the nose. Most air breathed in normally flows through the nose but only a small part reaches the olfactory clefts, enough to get a response to an odor. When a person sniffs to detect a smell, air moves faster through the nose, increasing the flow to the olfactory clefts and carrying more odor to these sensory organs.

The sense of smell is also influenced by something called the common chemical sense. This sense involves nerve endings in our eyes, nose, mouth, and throat, especially those on moist surfaces. Beyond smell and taste, these nerve endings help sense the feelings stimulated by different substances, such as the eye-watering onion or the refreshingly cool peppermint.

Flavors are recognized mainly through the sense of smell. Along with texture, temperature, and the sensations from the common chemical sense, the perception of flavor comes from a combination of odors and taste. Without the olfactory cells, familiar flavors like coffee or oranges would be harder to distinguish.