What process encompasses both inspiration and expiration in physiology?

The process that encompasses both inspiration and expiration in physiology is best described by the term "ventilation." Ventilation specifically refers to the mechanical process of moving air into and out of the lungs, which includes inhalation (inspiration) and exhalation (expiration). This process is crucial for the exchange of gases in the respiratory system, allowing oxygen to enter the body and carbon dioxide to be expelled.

While "respiration" might seem accurate since it relates to gas exchange, the term generally involves two components: the actual exchange of gases (external respiration at the alveoli and internal respiration at the cellular level) as well as ventilation. The key distinction is that ventilation focuses purely on the physical movement of air, whereas respiration covers the broader metabolic processes involving gas exchange, making ventilation the more precise term for the process described in the question.

Circulation refers to the movement of blood through the heart and blood vessels, and diffusion describes the passive movement of molecules from an area of higher concentration to one of lower concentration, which is relevant but not synonymous with the mechanical process of air movement. Thus, ventilation is the correct answer as it specifically includes both inspiration and expiration.