3.8.1: Diaphragm activity and lung volume -1

The diaphragm is an inspiratory muscle.

The red outlines show the lungs and the outer grey line shows the chest wall. The cavity inside the chest wall is the thoracic cavity. The diaphragm is at the bottom of the thoracic cavity. Red indicates that the diaphragm is contracting.

When the diaphragm contracts, the thoracic cavity increases in volume and inflates the lungs. This process is inspiration. The volume of gas inside the lungs is called 'lung volume'. With diaphragm contraction, the lung volume increases.
lung volume (within one quiet respiratory cycle)minmin→maxmax


1 The diaphragm is an expiratory inspiratory  muscle.

2 When expiratory muscles inspiratory muscles  such as the diaphragm contract, the lungs and the thoracic cavity decreases increases  in volume.

3 The lungs and thoracic cavity

increase in volume during inspiration and decrease in volume during expiration
increase in volume during expiration and decrease in volume during inspiration


: Diaphragm activity and lung volume -2

: respiratory cycle in English