HOSA Physical Therapy Practice Test 2025 – Comprehensive Exam Prep

The contraction of the muscles of respiration during the breathing process is known as inspiration. During this phase, the diaphragm and intercostal muscles contract, leading to an increase in the volume of the thoracic cavity. This increase in volume causes a decrease in internal pressure relative to the outside atmosphere, allowing air to flow into the lungs.

Inspiration is critical for bringing fresh air containing oxygen into the alveoli, the tiny air sacs in the lungs where gas exchange occurs. This process is essential for supplying oxygen to the bloodstream and removing carbon dioxide from the body. Understanding inspiration is fundamental for grasping the overall mechanics of respiration, as it directly contributes to the ventilation process, which encompasses both inspiration and expiration.

In contrast, expiration refers to the process of exhaling air and involves the relaxation of the diaphragm and intercostal muscles, leading to a decrease in the thoracic cavity volume. Ventilation is a broader term that includes both inspiration and expiration as the cycle of breathing. Respiration encompasses all processes related to gas exchange, including external respiration (exchange of gases in the lungs) and internal respiration (exchange of gases at the cellular level).