What Is the Role of the Diaphragm During Respiration?

The diaphragm, a large dome-shaped muscle in the chest, plays a major role in both passive and active respiration. Other muscles contribute to more active respiration when oxygen requirements increase.

Passive Inhalation

• When you breathe quietly, the diaphragm rises and falls in a passive manner. When it contracts, it drops lower in your chest, stretching the lungs and chest wall. The pressure in your lungs drops and automatically draws outside air into the respiratory tract.

Passive Exhalation

• When the lungs and chest wall relax, the diaphragm naturally rises to its resting position and pushes air out of the lungs.

Active Inhalation

• When you exercise or exert yourself, your body needs more oxygen than passive breathing can provide. As you take bigger breaths, accessory muscles in your neck, chest, and abdomen push out the ribs and sternum, and the diaphragm drops down further in the chest, allowing your lungs to expand further in volume and suck in more air.

Active Exhalation

• As you exhale during exertion, abdominal muscles become predominant. They contract harder, increasing pressure within the abdominal cavity, which drives the diaphragm upward and pushes air out of the lungs.

Other Considerations

• The lungs have no muscles of their own, which makes the role of the diaphragm and accessory breathing muscles vital in respiration. All these muscles depend on nerves connected to the brain to maintain respiration.