Answer:
1) This happens in the nasal cavity or nostrils. The cilia (nasal hairs) are the ones responsible for this in which the particles are filtered. Then in the back of the throat is where the nasal cavity and mouth meet is the pharynx.
2) This is the correct function. There are four stages of gas exchange that occur when oxygen is breathed into the body: ventilation, pulmonary gas exchange, gas transport, and peripheral gas exchange. The processes of gas inhalation, exhalation, exchange at the alveoli, transportation to the blood, and subsequent diffusion through different cellular membranes situated in body tissues are described. The lungs contain millions of alveoli, which are surrounded by capillaries. Each bronchiole ends with a collection of tiny air sacs known as alveoli. Capillaries, which are very small blood arteries, surround alveoli. These air sacs are filled with oxygen-rich air from the air you breathe in. The exchange of gases takes place here.
3) It travels down both, not just one. The air travels passed the larynx and into the trachea. The trachea is divided into two tubes which are known as the bronchial tubes. The left one leads to the left lung and the other to the right lung. From here the air is brought to even smaller tubes known as bronchioles.
4) Air enters from the outside during inhalation to either these two openings: nostrils or external nares. The cilia serve the purpose of capturing large inhalation particles. The internal nares are the openings between the nasal cavity and the pharynx. Hence, air enters into the nasal cavity.
5) From the pharynx, air flows through the glottis to the trachea and the cycle continues. The glottis and two or three other cartilages form the larynx, a simple tubular structure in most reptiles.
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