What term is defined as "gas exchange" in the context of pulmonary physiology?

• A. Ventilation
• B. Respiration
• C. Olfaction
• D. Diffusion

Answer: (B)

In pulmonary physiology, the term "respiration" refers specifically to the process of gas exchange, which involves the uptake of oxygen and the release of carbon dioxide at the alveolar level in the lungs. This process is essential for maintaining the body's oxygen supply and removing metabolic waste products.

Respiration encompasses two primary components: external respiration (gas exchange in the lungs) and internal respiration (gas exchange at the cellular level). It is vital to the process of supporting cellular metabolism throughout the body.

In contrast, ventilation is the movement of air in and out of the lungs, primarily involving the mechanics of breathing (inhalation and exhalation) rather than the exchange of gases themselves. Olfaction relates to the sense of smell and has no direct connection to gas exchange. Diffusion, while it is a mechanism involved in gas exchange, is a physical process that describes how oxygen and carbon dioxide move across the alveolar-capillary membrane; however, it does not encompass the broader concept of gas exchange as a whole. Thus, respiration is the most appropriate term to describe the overall gas exchange process in pulmonary physiology.