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How do the diaphragm and intercostal muscles help people breathe in?
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human respiratory system
The lungs serve as the gas-exchanging organ for the process of respiration.
In the human respiratory system, the diaphragm and external intercostal muscles act as the primary muscles of inspiration, functioning as an aspiration pump to draw air into the lungs.1
- The Diaphragm: This dome-shaped muscle separates the chest and abdominal cavities. When it contracts, it moves downward, which increases the vertical height of the thoracic cavity and depresses the abdominal organs.12
- The Intercostal Muscles: As the external intercostal muscles contract, they cause the ribs to rotate upward and laterally. This movement increases the overall circumference of the chest.1
Together, these actions expand the chest cavity, which lowers the pressure between the lungs and the chest wall, as well as the pressure within the lungs themselves. By increasing the volume of the thoracic cavity, these muscles create a pressure gradient that causes atmospheric air to flow into the lungs. This process relies on the physical principle that, at a constant temperature, the pressure of a gas varies inversely with its volume, a relationship known as Boyle’s law.123