The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the septal cartilage (which separates the nostrils) and the upper and lower lateral cartilages. On average the nose of a male is larger than that of a female.
The nose has an area of specialised cells which are responsible for smelling (part of the olfactory system). Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from entering the lungs. Sneezing is usually caused by foreign particles irritating the nasal mucosa, but can more rarely be caused by sudden exposure to bright light (called the photic sneeze reflex) or touching the external auditory canal. Sneezing can transmit infections, because it creates aerosols in which the droplets can harbour microbes.
