Question

To generate pressure gradients in order to facilitate expiration and inspiration, the human body uses the intercostal muscles and

• A. Alveolar sac
• B. Bronchi
• C. Primary, secondary and tertiary bronchioles
• D. Diaphragm
• E. Windpipe

Answer 1

The correct option is D Diaphragm

During inspiration, the diaphragm and a specialised set of intercostal muscles (external and internal) contract. This moves the lateral thoracic wall out ward and upward increasing the capacity of the thoracic cavity and thus generating the pressure gradient between the lungs and atmosphere leading to the movement of air into the lungs. During expiration, the diaphragm and the intercostal muscles relax. This moves the lateral thoracic wall inward and downward decreasing the capacity of the thoracic cavity, this leads to the expiration of air from the lungs.