Breathing Mechanics
Explore the diaphragm, chest muscles, and pressure changes that move air in and out of the lungs.
What drives airflow
Air moves in and out of the lungs because of pressure differences created by the diaphragm and the muscles between the ribs, known as the intercostal muscles.
The diaphragm during inhalation and exhalation
As the diaphragm contracts and flattens, the chest cavity expands and pulls air into the lungs.
The main muscle
The diaphragm is a dome-shaped muscle beneath the lungs that flattens and contracts during inhalation.
Rib movement
These muscles lift and expand the rib cage, helping increase the volume of the chest cavity.
Pressure drops
As the chest cavity expands, pressure inside the lungs drops below atmospheric pressure, drawing air in.
Pressure rises
As the diaphragm and rib muscles relax, chest volume decreases and pressure rises, pushing air out.
Breathing follows pressure, not the other way around.
Muscles change the volume of the chest cavity first; the resulting pressure difference is what actually moves air.
Quiet versus forceful breathing
During quiet breathing, the diaphragm does most of the work. During forceful breathing, such as during exercise, additional muscles in the neck, chest, and abdomen assist to move more air more quickly.
Why mechanics matter
Understanding breathing mechanics helps explain conditions that affect how easily the chest can expand, and why muscle weakness or restricted movement can make breathing more difficult.
Breathing is muscular before it is chemical.
Chemical signals in the brain control the muscles of breathing, but it is those muscles that physically move air.