Anatomy and Physiology of the nose:

Nasal Cavity function: Olfaction, filtration, heating and humidification:

The nose has two primary functions. The first is olfaction – the sense of smell. However, the second function is of primary interest to this discussion – filtration heating and humidification of the inhaled airTo accomplish the second task, the nasal cavity contains a convoluted set of passageways called the turbinates on the lateral wall of each nasal cavity (see cross-sectional CT scan of turbinates to right). These turbinates interrupt the flow of air into the nasal passage, forcing it through narrow passages that are covered with moist nasal respiratory mucosa. The total surface area available in the nasal mucosa is estimated to be about 180 cm2, of which 10 cm2 is olfactory mucosa and 170 cm2 is the richly vascularized respiratory mucosa. During the passage across this broad mucosal surface, the air is warmed and humidified by a rich vascular capillary bed that is directly beneath the surface see diagram to left). These capillaries are specifically designed for rapid passage of fluids through the vascular wall and out into the dry air.[1-3] The amount of blood flow to this area is considerable – it is higher per unit of tissue than the blood flow to the brain, liver or muscle.