Nose

The nose is an external protrusion of the human respiratory and olfactory systems, allowing the intake and outgo of air and the ability to expel mucus. It's shape is formed by the ethmoid bone and the nasal septum, which is made primarily of cartilage. 
Humans prefer to breathe through their noses rather than their mouths as air going through the nose is heated, humidified and filtered by the surfaces and hairs therein. The interior of the nostrils also contain special cells which are responsible for the sense of smell. 
The interior of the nose is sensitive and irritation will cause sneezing. It is also susceptible to bleeding due to the capillaries in the nose being very close to the surface. It is also vulnerable to infection, which can cause congestion and often results in passing off infections to others. 
Human nose at WikipediaCategory:Anatomy