The mechanism of respiration primarily involves the coordinated movement of muscles that facilitate the intake of air into the lungs (inhalation) and the expulsion of air out of the lungs (exhalation).
How Breathing Works: The Process of Respiration
Respiration, specifically breathing or ventilation, is a mechanical process that relies on pressure changes to move air in and out of the lungs. This process can be broken down into two main phases: inhalation and exhalation. The key players in this process are the diaphragm and the intercostal muscles, which are located between the ribs.
Inhalation (Breathing In)
- Muscle Contraction: During inhalation, the diaphragm, a large, dome-shaped muscle located beneath the lungs, contracts and pulls downward. Simultaneously, the muscles between the ribs contract and pull upward.
- Chest Cavity Expansion: These muscle movements cause the chest cavity (thoracic cavity) to expand in size.
- Pressure Reduction: The increase in the size of the thoracic cavity leads to a decrease in the pressure within the lungs.
- Air Intake: Because the pressure inside the lungs is now lower than the atmospheric pressure outside, air rushes into the lungs to equalize the pressure. This is the process of taking a breath in.
Exhalation (Breathing Out)
- Muscle Relaxation: During exhalation, the diaphragm and intercostal muscles relax.
- Chest Cavity Contraction: The thoracic cavity decreases in size.
- Pressure Increase: This decrease in volume leads to an increase in pressure within the lungs.
- Air Expulsion: Because the pressure inside the lungs is now higher than the atmospheric pressure, air is forced out of the lungs. This is the process of breathing out.
A Summary of the Process
The following table outlines the mechanics of inhalation and exhalation
| Process | Muscle Action | Thoracic Cavity Volume | Pressure in Lungs | Air Movement |
|---|---|---|---|---|
| Inhalation | Diaphragm contracts, intercostal muscles contract | Increases | Decreases | Inward |
| Exhalation | Diaphragm relaxes, intercostal muscles relax | Decreases | Increases | Outward |
In essence, the act of respiration is a continuous cycle of these two phases, ensuring that the body receives the necessary oxygen and expels carbon dioxide. The rhythmic movement of the diaphragm and the intercostal muscles is involuntary, controlled by the respiratory center in the brainstem.
