The movement of the diaphragm causes air to go in and out of the lungs by changing the volume and pressure inside the chest cavity. When the diaphragm contracts, it flattens and moves downward, increasing the volume of the chest cavity and creating a negative pressure (vacuum) inside the lungs. This lower pressure compared to the outside air causes air to flow into the lungs (inhalation). When the diaphragm relaxes, it moves back to its dome shape, decreasing the chest cavity volume, increasing the pressure inside the lungs, and pushing air out (exhalation). This cycle of diaphragm contraction and relaxation drives the flow of air in and out of the lungs during breathing.
How the diaphragm causes air to enter lungs (inhalation)
- Diaphragm contracts and flattens downwards.
- This expands the chest cavity, lowering internal pressure.
- Air moves from outside (higher pressure) into lungs (lower pressure).
How the diaphragm causes air to leave lungs (exhalation)
- Diaphragm relaxes and moves upward into dome shape.
- Chest cavity volume decreases, increasing pressure in lungs.
- Air is pushed out from lungs to the outside (higher pressure inside than outside).
This process is the main mechanism of normal, quiet breathing and is assisted by other muscles for deeper breaths or forced exhalation.
