RLO: Ventilation

School of Nursing and Academic Division of Midwifery

Exhalation (at rest)

Exhalation at rest is a passive process. It commences when the respiratory muscles relax. The diaphragm resumes it’s bell-shape and pushes up on the lower wall of the lungs while the external intercostal muscles relax allowing the ribs and sternum to swing back to their original position.

When the parietal pleura moves inwards with the chest wall during exhalation, it presses on the pleural cavity which creates a rise in intrapleural pressure. This slackens the outward pull on the visceral pleura which enables elastin fibres in the lung tissue to recoil. As a result, the lungs decrease in volume, pushing air out into the atmosphere as they do so.