What happens to the ribcage during passive expiration?

During passive expiration, the ribcage primarily remains stationary as the process is largely driven by the relaxation of the diaphragm and intercostal muscles, rather than active muscular contraction. When you breathe in, these muscles contract to expand the thoracic cavity and allow air to fill the lungs. During passive expiration, after the diaphragm relaxes, the elastic recoil of the lung tissue and the thoracic cavity assist in pushing air out of the lungs. This results in a decrease in thoracic volume and pressure, facilitating airflow out of the lungs without significant movement of the ribcage itself. Thus, the passive action of expiration does not involve the ribcage actively expanding or collapsing, contributing to the understanding of respiratory mechanics.