During quiet breathing, what percentage of air flow through the lungs is attributed to the diaphragm?

During quiet breathing, the diaphragm plays a crucial role in the process of inhalation. It is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity and is the primary muscle responsible for respiratory function at rest.

When the diaphragm contracts, it flattens and moves downward, increasing the volume of the thoracic cavity. This increase in volume reduces the pressure inside the lungs, allowing for air to flow in from the higher-pressure environment outside. The diaphragm's contraction accounts for approximately two-thirds of the air volume that is inhaled during quiet breathing. This is why the correct answer reflects that around 66% of airflow through the lungs is attributed to diaphragmatic movement during this state.

Other muscles, such as the intercostal muscles, assist in expanding the chest further, but their contribution is secondary to that of the diaphragm during quiet breathing.