Question

(a) Explain how, the air we breathe in gets cleaned while passing through the nasal passage.
(b) Why do the walls of trachea not collapse when there is less air in it?
(c) How are oxygen and carbon dioxide exchanged in our body during respiration?
(d) How are lungs designed in human beings to maximise the exchange of gases?

Answer 1

(a) The nasal passage is lined with fine hair and mucus. When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by the nasal hair and mucus. Due to this, only clean air reaches the lungs.

(b) The walls of trachea do not collapse when there is less air in it because trachea is supported by rings of soft bones called cartilage.

(c) Gaseous exchange in our body takes place in the alveoli of lungs. The oxygen of air diffuses out from the alveoli walls into the blood. As the blood passes through the tissues of the body, the oxygen present in it diffuses into the cells. This oxygen combines with the digested food present in the cells, to release energy. Carbon dioxide gas, which is produced as a waste product during respiration in the cells of the body tissues, diffuses into the blood. Blood carries the carbon dioxide back to the lungs, where it diffuses into the alveoli.

(d) The human lungs have been designed to maximise the exchange of gases.
There are millions of alveoli in the lungs. The presence of millions of alveoli in the lungs provide a very large area for the exchange of gases. The availability of large surface area maximises the exchange of gases.