Nose

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From Wikipedia, the free encyclopedia
For other uses, see Nose (disambiguation).
For the article about noses in humans, see human nose.
Nose

Dogs have very sensitive noses
Latin 'Nasus'
Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. Behind the nose are the olfactory mucosaand 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.[citation needed]
Contents [hide]
1 Air conditioning
2 Sense of direction
3 Structure in air-breathing forms
4 In fish5 See also
6 References
7 External links
[edit]Air conditioning

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, also for flicking if moving and by mostly reclaiming moisture from the air before it is exhaled (as occursmost efficiently in camels). The nose often has inner hairs whose function is to stop unwanted particles from entering the lungs.
[edit]Sense of direction

The wet nose of dogs is useful for the perception of direction. The sensitive cold receptors in the skin detect the place where the nose is cooled the most and this is the direction a particular smell that the animal just picked up comesfrom.[1]
[edit]Structure in air-breathing forms



The nose of a tapir.
In amphibians and lungfish, the nostrils open into small sacs that, in turn, open into the forward roof of the mouth through the choanae. These sacs contain a small amount of olfactory epithelium, which, in the case of caecilians, also lines a number of neighbouring tentacles. Despite the general similarity in structure tothose of amphibians, the nostrils of lungfish are not used in respiration, since these animals breathe through their mouths. Amphibians also have a vomeronasal organ, lined by olfactory epithelium, but, unlike those of amniotes, this is generally a simple sac that, except in salamanders, has little connection with the rest of the nasal system.[2]
In reptiles, the nasal chamber is generallylarger, with the choanae being located much further back in the roof of the mouth. In crocodilians, the chamber is exceptionally long, helping the animal to breathe while partially submerged. The reptilian nasal chamber is divided into three parts: an anterior vestibule, the main olfactory chamber, and a posterior nasopharynx. The olfactory chamber is lined by olfactory epithelium on its upper surfaceand possesses a number of turbinates to increase the sensory area. The vomeronasal organ is well-developed in lizards and snakes, in which it no longer connects with the nasal cavity, opening directly into the roof of the mouth. It is smaller in turtles, in which it retains its original nasal connection, and is absent in adult crocodilians.[2]
Birds have a similar nose to reptiles, with thenostrils being located at the upper rear part of the beak. Since they generally have a poor sense of smell, the olfactory chamber is small, although it does contain three turbinates, which sometimes have a complex structure similar to that of mammals. In many birds, including doves and fowls, the nostrils are covered by a horny protective shield. The vomeronasal organ of birds is either under-developedor altogether absent, depending on the species.[2]


Elephants have prehensile noses.
The nasal cavities are exceptionally large in most mammals, typically occupying up to half the length of the skull. In some groups, however, including primates, bats, and cetaceans, the nose has been secondarily reduced, and these animals consequently have a relatively poor sense of smell. The nasal cavity...
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