Nose

Anatomically, a nose is a protuberance in that houses the nostrils, or nares, which admit and expel air for respiration.

Function

In mammals

In most mammals, it also houses the nosehair, which catch airborne particles and prevent them from reaching the lungs. Within and behind the nose is the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the digestive system, and then into the rest of the respiratory system. In humans, the nose is located centrally on the face; on most other mammals, it is on the upper tip of the snout.

As an interface between the body and the external world, the nose and associated structures frequently perform additional functions concerned with conditioning entering air (for instance, by warming and/or humidifying it) and by reclaiming moisture from the air before it is exhaled (as occurs most efficiently in camels).

In most mammals, the nose is the primary organ for smelling. As the animal sniffs, the air flows through the nose and over structures called turbinates in the nasal cavity. The turbulence caused by this disruption slows the air and directs it toward the olfactory epithelium. At the surface of the olfactory epithelium, odor molecules carried by the air contact olfactory receptor neurons which transduce the features of the molecule into electrical impulses in the brain.

Associated health risks

Because of the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain. For this reason, the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla, is known to doctors as the danger triangle of the face.

Direction finding

All humans have a trace amount of magnetite in their noses, found in the ethmoid bone (between the eyes), possibly part of a rudimentary compass to allow direction finding relative to the earth's magnetic field. The human magnetoception is still very controversial, but some studies show that some people have the ability to orient themselves-even when blindfolded and removed from such external clues as sunlight-to within a few degrees of the North Pole, exactly as a compass does.^{[citation needed]}

References

Physical Manual: Univ. of Tennessee at Martin

External links

WebMD: The Sinuses and The Nose
From the Nose to the Eustachian Tube: Information, videos, tips for diving
Your Nose: The Guardian Of Your Lungs
Asian Noses This website discusses the differences in Asian noses.