The Nose
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 Functions of the nose
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Functions of the nose


As part of the respiratory system, the nose serves several functions. The nose is the organ of smell and a main passageway for air into and out of the lungs. The nose warms, moistens, and cleans the air before it enters the lungs.
 

Smell

Smell is one of the most important functions of the nose. This sense is mediated by specialized sensory cells called olfactory epithelium in the upper part of the nasal cavity (superior nasal turbinates). Molecules of odorants passing through the superior nasal turbinates dissolve in the mucus lining the superior portion of the cavity and are detected by receptors (olfactory receptors) on specialized nerve cells. These nerve cells have hair-like structures called cilia. The cilia of each cell are sensitive to different chemicals and, when stimulated, create a nerve impulse that is sent to the nerve cells of the olfactory bulb, which lies inside the skull just above the nose. The olfactory nerves carry the nerve impulse from the olfactory bulb directly to the brain, where it is perceived as a smell.



Although not fully understood, the sense of smell is much more sophisticated than the sense of taste. Distinct smells are far more numerous than tastes. The subjective sense of taste while eating involves both taste and smell. This is why food seems somewhat tasteless when a person has a decreased sense of smell, as may occur when the person has a cold. Moreover, it is during exhalation that the olfaction contribution to taste occurs in contrast to that of proper smell which occurs during the inhalation phase. Because the smell receptors are located in the upper part of the nose (superior nasal turbinates) normal breathing does not draw much air over them. Sniffing, however, increases the flow of air over the smell receptor cells (olfactory epithelium), greatly increasing their exposure to odors.

Interestingly, the importance of smell is known as a key component for memories, physical attraction and emotional connections.

See also: Other benefits of breathing through the nose