Final answer:
The nose contributes roughly two-thirds, or 2/3, of the resistance to breathing, which helps in filtering, warming, and moistening inhaled air and allows more efficient oxygen extraction during exhalation.
Step-by-step explanation:
The nose provides approximately two-thirds, or 2/3, of the total airway resistance to breathing. When you breathe in, or during inspiration, the nasal passages help to filter, warm, and moisten the air, which is advantageous especially in cold and dry conditions. The smaller diameter of the nasal passages compared to the mouth plays a significant role in creating this resistance and heightens the pressure in the lungs during exhalation, or expiration. This process allows the lungs more time to extract oxygen from the air.
Different factors can influence the amount of resistance provided by the nasal passages, such as congestion from allergies or a cold, which can increase resistance and make it more difficult to breathe through the nose.