The nose also reabsorbs heat and vapor from expired air. In cold day, the breath from mouth is warmer and more whitish than that from nose. The body's need for oxygen varies considerably and depends on many factors. Internal and external factors decide the extent and nature of nasal respiration. On the one hand is varying need for oxygen for cellular respiration, and on the other is the necessity to react to climate and environmental situations.
Outer environment changes the oxygen demand.
Nasal cavity changes the resistance physiologically. In nasal cavity there are swellings from lateral wall. Turbinates make the surface of nasal mucosa wide and inspiratory air is humidified and thermalized effectively. Increase of nasal blood flow enlarges the turbinate's volume, and changes the resistance of nasal cavity. For pathological nasal stop, we take operation to the lateral wall of nasal cavity.