What causes exhalation?
In respect to this, what happens during exhalation?
The process of breathing (respiration) is divided into two distinct phases, inspiration (inhalation) and expiration (exhalation). During expiration, the diaphragm relaxes, and the volume of the thoracic cavity decreases, while the pressure within it increases. As a result, the lungs contract and air is forced out.
Furthermore, what causes expiration?
Inspiration occurs when intrapulmonary pressure falls below atmospheric pressure, and air moves into the lungs. Expiration occurs when intrapulmonary pressure is increased above atmospheric pressure. After the diaphragm contracts, it relaxes, thus decreasing thoracic volume and increasing intrapulmonary pressure.
In relaxed breathing the ribs are lifted by external intercostal muscles. Lifting the ribs expands the thoracic cavity walls, and lowering the floor also increases the thoracic cavity space. Exhalation in the relaxed state involves the recoil of the tissues to their pre-inhalation position.