What's the difference between breathing through your mouth and breathing through your nose?

I am a medical student. Let me explain something to you. Textbook knowledge is for reference only:

The pharynx is divided into three parts: nasopharynx, oropharynx and larynx. The first two parts have the same channel, which is the larynx. In view of the different anatomical structures of nasopharynx and oropharynx, the distribution of lymphoid tissue is different, but the treatment of external air is different. Under normal circumstances, we breathe through our noses. From the structure of the nose, we can know that it handles the air, avoids body infection, and has a stronger protective function for the body. Breathing through the mouth can cause discomfort such as dry mouth. Smoking, whether you use your nose or not. Feeling upset in the stomach is also the same result, because smoking will excite the vagus nerve, leading to corresponding clinical symptoms, such as increased gastrointestinal smooth muscle movement and slow heart rate. Smoking is harmful to health, so it is recommended to smoke less or not. ! Not much to say, I'm getting off, haha!