AP BIOLOGY

Detailed explanation-1: -During exhalation is alveolar pressure upper than atmospheric (when inspiration muscles relax than elasticity of lungs dominates and the thoracic volume and lungs volume decreases and alveolar pressure becomes positive).

Detailed explanation-2: -Inspiration can occur if the pressure within the lungs (intrapulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. Similarly, expiration takes place when the intrapulmonary pressure is higher than the atmospheric pressure.

Detailed explanation-3: -During exhalation, the diaphragm also relaxes, moving higher into the thoracic cavity. This increases the pressure within the thoracic cavity relative to the environment. Air rushes out of the lungs due to the pressure gradient between the thoracic cavity and the atmosphere.

Detailed explanation-4: -If the pressure is greater in the lungs than outside the lungs, then air rushes out. If the opposite occurs, then air rushes in. Here is a summary of the process: Inspiration occurs when the inspiratory muscles-that is, the diaphragm and the external intercostal muscles-contract.

Detailed explanation-5: -When the lungs exhale, 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.