Final answer:
During inspiration, the diaphragm contracts and lowers while the external intercostals contract, causing the rib cage to expand and elevate, leading to a decrease in intrathoracic pressures and allowing air to flow into the lungs.
Step-by-step explanation:
During the process of inspiration, several physiological changes occur that involve the diaphragm, intercostal muscles, rib cage, and pressures within the thoracic cavity. When breathing in, the diaphragm contracts and descends, while the external intercostal muscles contract, causing the rib cage to move upward and outward.
This action expands the thoracic cavity and thereby decreases the intrapleural pressure and intrathoracic pressures. As a result of this pressure decrease, air flows into the lungs (inflow) due to the creation of a pressure gradient between the atmosphere and the inside of the lungs.
Inhalation and Pressure Changes
The sequence of events during inspiration leads to a series of pressure changes: The diaphragm contraction results in a decreased intrathoracic pressure, and the expansion of the rib cage contributes to this pressure reduction.
Due to Boyle's Law, as the intrathoracic volume increases, the pressure decreases, pulling air into the lungs. The inhalation process continues until the pressure within the lungs equals the outside atmospheric pressure.