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Nares are the external openings of the nose, better known to many laypeople as the nostrils. The nares connect to the nasal passages, allowing animals to inhale through their noses. In addition to being an opening for the intake of air to breathe, the nostrils are also used for smelling, with odor-sensitive organs located inside the nose to process and interpret olfactory information. This information is used for everything from pursuing prey to identifying milk that has gone off and should not be consumed.
A single nostril is known as a naris. The nose actually has two sets of nostrils, with the second set located inside the nose where they are not visible. The nares are separated by a structure known as the septum. In some people, the septum is crooked or broken down, and this can interfere with breathing. In some cases, the septum is absent or significantly damaged and instead of having two nasal passages, people effectively have one large open cavity inside the nose.
The nares are lined with fine hairs that are designed to trap particulates so that they cannot enter the trachea and the lungs. They are also lined with mucus produced by the cells inside the nasal cavity. The mucus keeps the nostrils lubricated so they do not dry out as air passes by, and it also acts to snag material before it hits the trachea so the lungs are not irritated by pollen, dust, and other materials.
The size and shape of the nares can vary considerably between people and is dependent in part on the overall shape of the nose. Sometimes people choose to have cosmetic surgery on the nose to change the shape of the nose or nostrils for aesthetic reasons. Plastic surgery is also used to reconstruct the nose if it has been injured and to address congenital defects that interfere with the ability to breathe comfortably. Surgical procedures may also be performed on people with sleep disorders related to variations in the structure of the nose to address the disorder and help the patient breathe more easily.
In addition to serving a number of biological functions, the nares can also serve as a handy point for delivering medication. The nose absorbs medications readily through its mucus membranes, and some drugs are prepared as nasal sprays or inhalers that are puffed into the nose. Medications can also be rubbed inside the nose. Delivery through the nose allows drugs to be quickly absorbed into the bloodstream so that they can start working quickly.