Here's how it works:
1. Inhalation:
- The diaphragm, a large muscle beneath the rib cage, contracts and flattens downward.
- The intercostal muscles (between the ribs) also contract, pulling the ribs upwards and outwards.
- This combined action increases the volume of the chest cavity.
- This increase in volume creates a lower pressure inside the lungs compared to the atmosphere, causing air to flow into the lungs through the trachea and bronchi.
2. Exhalation:
- The diaphragm relaxes, returning to its dome shape.
- The intercostal muscles relax, allowing the ribs to move downwards and inwards.
- These movements decrease the volume of the chest cavity, increasing the pressure inside the lungs.
- This higher pressure forces the air out of the lungs through the same pathways.
The rib cage's role is essential because:
* Provides structural support for the lungs: The rib cage acts as a protective cage, preventing the lungs from collapsing.
* Allows for volume changes: The flexible nature of the rib cage, coupled with the movements of the diaphragm and intercostal muscles, allows for efficient changes in chest cavity volume, which drives the flow of air into and out of the lungs.
Gas exchange itself occurs in the alveoli, tiny air sacs within the lungs. The oxygen from inhaled air diffuses across the thin walls of the alveoli into the bloodstream, while carbon dioxide from the blood diffuses into the alveoli to be exhaled.
In summary, the rib cage, in conjunction with the diaphragm and intercostal muscles, creates the necessary pressure gradients and volume changes for breathing, which ultimately allows for efficient gas exchange in the lungs.
