Nasal passage: A channel for airflow through the nose. The walls of the nasal passages are coated with respiratory mucous membranes, which contain innumerable tiny hair-like cells that move waves of mucus toward the throat. Dust, bacteria, and other particles inhaled from the air are trapped by the mucus in the nose, carried back, swallowed, and dropped into the gastric juices so that any potential harm they might do is nullified. The organs of smell are made up of patches of tissue called olfactory membranes. The olfactory membranes are about the size of a postage stamp and are located in a pair of clefts just under the bridge of the nose. Most air breathed in normally flows through the nose, but only a small part reaches the olfactory clefts 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.