Breathing is the process of letting in oxygen from the air into the lungs and CO2 out of the lungs.
Mechanism: Involuntary, rate controlled by the brain. outward and inward movement of ribs increases or decreases the space of thoracic cavity, action assisted by diaphragm continuous inhalation and exhalation of the air.
Detailed Answer:
A physical process by which oxygen is taken in and carbon dioxide is given out is called breathing.
Breathing in humans involves three steps :
(i) Inspiration: When we breathe in, ribs move up and flatten the diaphragm due to which the chest cavity becomes larger. As a result, air is sucked into the lungs and fills the expanded alveoli.
(ii) Gaseous exchange: Haemoglobin binds with the oxygen and carries it along the blood in the body. As blood passes through the tissues of the body, oxygen from the blood diffuses into the cell, whereas carbon dioxide which is produced during respiration diffuses into the blood and is carried to the lungs for expiration.
(iii) Expiration: Itibs move down and diaphragm becomes dome-shaped decreasing the chest cavity. Thus, pushing the air out from lungs.
