One of the functions of the nose is responsible for breathing, that is, inhaling oxygen and exhaling carbon dioxide. The idiom "spit out the old and bring in the new" is the most incisive summary. Although most people know that people have two lungs, that is, the left lung and the right lung, it is little known that each lung is controlled by its corresponding nostril on the same side. If the left nostril is temporarily blocked, the left lung will have to compete with the right lung and exchange gas with the help of the right nostril. In other words, when one nostril is blocked and unable to ventilate, as an accurate protection mechanism of nasal reflex of human respiratory system, the breathing process will completely transfer to the other nostril-one of them.

Secondly, two nostrils can make breathing exercise more effective, thus promoting the metabolism of the whole human body.

Third, breathing through two nostrils can take turns to rest, while working through one nostril is extremely tiring. Research data show that if you breathe through only one nostril, you will feel tired after working for 3 hours.

fourthly, two nostrils help you sleep. If you stay in a sleeping position for more than 8 hours, it will change compared with standing because of gravity, and one nostril will usually be blocked. Therefore, the nostrils can sleep more relaxed in pairs, and even if one nostril is temporarily blocked, the human body can easily cope.

these four reasons are enough to show the physiological advantages of two nostrils. Obviously, the creator complied with this physiological need of human beings and made such a clever design, which can be described as the blessing of human body.