Question

Explain the process of breathing in humans.

Answer 1

Breathing is the process by which humans and other living beings take in oxygen from its environment and release carbon dioxide.

The main organ used by humans for breathing is lungs. There is a pair of lungs located in the chest. Each lung contains millions of small air sacks called alveoli.

The lung sucks the air from the environment through the process of inhalation (breathing in) by the action of contraction of diaphragm and chest muscles. This causes the lungs to expand and the air is sucked in. The air enters the lungs through the nose and the mouth and passes through the windpipe (trachea). This air which contains about $20\%$ oxygen and $0.3\%$ carbon dioxide, comes in contact with blood capillaries in alveoli, causing blood to absorb oxygen from the air inhaled and release carbon dioxide.

The process of inhalation is followed by the process of exhalation (breathing out) in which the diaphragm and chest muscles relax. With this, the air in the lungs is forced out of the lungs. This exhaled air contains about $17\%$ oxygen and $5\%$ carbon dioxide. This completes one cycle of breathing.

These cycles of inhalation and exhalation continue one after the other.