Form the main external opening and are a structure of bone, cartilage, skin and muscle that extends from the face and form two openings called nostrils, or napes. The nostrils lead to two cavities called navel cavities separated by the septum, a cartilage wall. On the roof of the nasal cavity is a special type of tissue called the olfactory epithelium, which specialises in producing a sense of smell. The olfactory epithelium is a sheet of cells that cover the underlying tissue of the nasal cavity. It is unique, as it contains many sensory cells that protrude from its surface and are embedded in mucus secreted by goblet cells in the epithelium. Within the sheet of the olfactory epithelium, there are several distinct cells. The cell that is responsible for sending sensory signals to the brain is the olfactory receptor neuron.
The nose is also the first line of defence against sickness. As air moves over the mucous, the air is warmed and humidified not to shock the delicate lungs. The Motile cilia or Moving cilia have a rhythmic waving or breathing motion that help to keep the airway clear of mucus and dirt so that breathing is easy and without irritation.
Nose breathing brings a focus to the brain.