What Is Breathing?
The process in which air moves in and out of the lungs is known as breathing. This is carried out through various respiratory organs. In other words, breathing is a simple give and take process.
When we breathe, we take in air rich in oxygen from the atmosphere, in return of which, we give out carbon dioxide-rich in the atmosphere which is utilized by the plants for photosynthesis.
This is a continuous process and goes on throughout the life of an organism.
The process of taking in oxygen-rich air is called inhalation. On the contrary, the process of giving out air that is rich in carbon dioxide is known as exhalation.
In a day, a person breathes several times. One breath comprises one inhalation and one exhalation. In a minute, the number of times a person breathes is termed as his/her breathing rate. By calculating the breathing rate, we can know the number of times we breathed in a day.
However, the breathing rate varies which is dependant upon a person’s activity. It raises when a person is brisk walking, running or after a heavy exercise; similarly, decreases when a person is calm.
The breathing rate of an adult is 15-18 times per minute. However, during heavy exercise, breathing rate exceeds 25 times per minute.
Mechanism Of Breathing
The air which we breathe in and out of the lungs varies in its pressure. So basically when there is a fall in air pressure the alveolar spaces falls and the air enters the lungs (inspiration) and as the pressure of the alveoli within exceeds the atmospheric pressure, the air is blown from the lungs (expiration). The flow rate of air is in proportion to the magnitude of the pressure difference.
The breathing mechanism involves two processes:
Inspiration
Expiration
Inspiration
In the process of inspiration, there would be a contraction of muscles attached to the ribs on the outer side which pulls out the ribs and results in the expansion of the chest cavity.
Later, the diaphragm, contracts, moves downwards and expands the chest cavity resulting in the contraction of the abdominal muscles.
The expansion of the chest cavity produces a partial vacuum which sucks air into the lungs and fills the expanded alveoli.
Mechanism Of Inspiration
The process of intake of atmospheric air is known as inspiration. It is an active process.
When the volume of the thoracic cavity increases and the air pressure decreases, inspiration takes place.
Contraction of external intercostal muscles increases the volume of the thoracic cavity.
Contraction of the diaphragm further increases the size of the thoracic activity. Simultaneously, the lungs expand.
With the expansion of the lungs, the air pressure inside the lungs decreases.
The pressure equalizes and the atmospheric air rushes inside the lungs.
Expiration
The expiration process is considered once after the gaseous exchange occurs in the lungs and the air is expelled out. This expulsion of air is called expiration.
During this process, muscles attached to the ribs contract, the muscles of the diaphragm and the abdomen relax which leads to a decrease in the volume of the chest cavity and increases the pressure of the lungs, causing the air in the lungs to be pushed out through the nose.
Mechanism Of Expiration
The process of exhaling carbon dioxide is called expiration. It is a passive process.
It occurs when the size of the thoracic activity decreases and the air pressure outside increases.
Now the external intercostal muscles relax and the internal intercostal muscles contract.
As a result, the ribs are pulled inwards and the size of the thoracic cavity is reduced.
The diaphragm is relaxed and the lungs get compressed.
Consequently, the pressure increases and the air is forced outside.
Mechanism of Respiration
Mechanism of respiration involves the breathing mechanism and exchange of gases.
The gaseous exchange occurs by diffusion in the alveoli. It depends upon the pressure differences between blood and tissues, or atmospheric air and blood. The exchange of gases takes place at the surface of the alveolus.
The mechanism of breathing has already been explained above. Let us have a look at the steps involved in the exchange of gases.
