What type of movement describes when air enters and exits the lungs?

Ventilation is the term that specifically refers to the movement of air into and out of the lungs. This process includes two key phases: inhalation (the act of taking air into the lungs) and exhalation (the act of expelling air from the lungs). Understanding ventilation is crucial as it is directly related to the respiratory system's primary function of gas exchange, where oxygen is brought into the body and carbon dioxide is removed.

The other options detail related but distinct processes. Diffusion is primarily the movement of molecules from an area of higher concentration to one of lower concentration, such as how oxygen moves from the alveoli into the blood. Oxygenation involves the process of hemoglobin binding with oxygen, which occurs after ventilation has taken place. Inhalation and exhalation describe specific parts of the ventilation process but do not encompass the entire movement of air, which is why ventilation is the correct and all-encompassing term.