During exhalation, which of the following processes occurs?

During exhalation, the primary process that occurs is the diffusion of carbon dioxide (CO2) from the blood into the lungs. As we breathe out, the muscles involved in respiration relax, allowing the lungs to expel air. This air contains a higher concentration of CO2, which has been produced by the body's metabolic processes.

In the alveoli of the lungs, where gas exchange occurs, the gradient—in which the concentration of CO2 is higher in the blood than in the alveoli—facilitates the diffusion of CO2 from the bloodstream into the airspaces of the lungs. Consequently, exhalation helps to rid the body of excess CO2, a waste product of cellular respiration, and maintain homeostasis in the body's acid-base balance.

Understanding this process highlights the importance of exhalation not only for oxygen exchange but particularly for the removal of carbon dioxide, which is vital for maintaining metabolic balance.