Mechanism of Breathing in Humans

Breathing is the process of inhaling and exhaling air from the lungs. The mechanism of breathing in humans involves the following steps:

Inhalation:
- The process of inhalation begins when the diaphragm, a dome-shaped muscle located at the bottom of the chest, contracts and moves downward.
- This creates more space in the chest cavity, causing the lungs to expand and fill with air.
- At the same time, the muscles between the ribs contract, pulling the ribs up and outwards and further increasing the space in the chest cavity.
- As a result of these actions, the air pressure inside the lungs decreases, causing air to rush in through the nose and mouth and down the trachea, or windpipe, into the lungs.

Exhalation:
- The process of exhalation begins when the diaphragm and rib muscles relax, causing the chest cavity to decrease in size.
- This decreases the space in the lungs, forcing air out of the lungs and up the trachea and out through the nose and mouth.
- During normal exhalation, the diaphragm and rib muscles relax passively, allowing air to be pushed out of the lungs by the elastic recoil of the lung tissue.

Control of Breathing:
- The process of breathing is controlled by the respiratory center, located in the brainstem.
- The respiratory center receives information about the levels of oxygen and carbon dioxide in the blood and adjusts breathing rate and depth accordingly.
- When the levels of carbon dioxide in the blood rise, the respiratory center signals the diaphragm and rib muscles to increase the rate and depth of breathing in order to remove excess carbon dioxide from the body.
- Conversely, when the levels of oxygen in the blood rise, the respiratory center signals the diaphragm and rib muscles to decrease the rate and depth of breathing to conserve oxygen.

In conclusion, the mechanism of breathing in humans involves the diaphragm and rib muscles working together to create changes in the space within the chest cavity, allowing air to flow in and out of the lungs. This process is controlled by the respiratory center in the brainstem, which adjusts breathing rate and depth based on the levels of oxygen and carbon dioxide in the blood.