Draw the human respiratory system and label the following parts:
(a) Trachea
(b) Alveoli
(C ) Respiratory bronchioles
(d) Larynx.
Describe in brief the role of lungs in the exchange of gases.

Explanation

Human respiratory system:

Role of lungs:
(i) When we breathe in air, the diaphagram contracts which results in the increase of chest cavity. Due to this expansion of chest cavity, the air pressure in the lungs decreases. Thus, air from outside rushes into the lungs through nostrils, trachea and bronchi. Thus sacs of lungs get filled with air when we breathe in. The exchange of gases between alveoli and blood takes place by the process of diffusion.
(ii) Now the air present in air sacs of the lungs is rich in `CO_(2)`. When we breathe out air, the diaphagram relaxes which result in the decrease of chest cavity. This contraction pushes the air from the lungs into the traches, nostrils and then out of the body into air. Breathing in of air is called inhabitation and breathing out of air is called exhalation.