Nasal anatomy and the sense of smell.

As a result of the relative sizes of the various compartments in the nasal cavity, the bulk of the airflow is along the floor of the nasal cavity. The percent of airflow directed to the olfactory region (the superior region of the nasal cavity) is about 10%. Structural changes in the nasal cavity can alter airflow pathways and the characteristics of the airflow (e.g. laminar, mixed or turbulent) within nasal compartments. The relationship between the olfactory response and the stimulus is complex and may vary depending on the physiochemical properties of the odor and the rate at which odorants are delivered to the olfactory receptors. Changes in nasal airflow may impact the various olfactory functions (e.g. identification, differentiation) differently. When there is a nasal obstruction, a decline in olfactory ability may not simply be an access problem, since nasal disease can affect olfactory processing at many levels.