Answer:
Human respiratory
system: The human respiratory system begins from nose cavities called nostrils.
The air from cavity enters into the pharynx and then into the trachea (or wind
pipe). The trachea runs down the neck and divides into two tubes called
bronchi. Each bronchi is connected to a lung. In the lungs each bronchi divides
into a large number of thin tubes called bronchioles. The bronchioles have a
tiny air sac at their ends called alveoli. It is in the alveoli where exchange
of gases takes place.
Mechanism of breathing:
(i) When we breathe in air, the diaphragm contracts which
results in the increase in volume 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. Therefore, air
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 CO2. When we breathe out air, the diaphragm relaxes which results
in the decrease in volume of chest cavity. This contraction pushes the air from
the lungs into the trachea, nostrils and then out of the body into air.
Breathing in air is called inhalation and breathing out air
is called exhalation.
Mechanism of gaseous exchange during respiration: The
oxygen is carried by blood to all the parts of the body. As the blood passes
through the tissues of the body, the oxygen from the blood diffuses into the
cell, whereas the CO2 which is produced during respiration diffuses
into the blood and is carried to the lungs.
You need to login to perform this action.
You will be redirected in
3 sec