What does external respiration involve?

External respiration specifically refers to the process of gas exchange that occurs in the lungs. This involves taking in oxygen from the air and transferring it to the bloodstream, while simultaneously allowing carbon dioxide, which is a waste product of metabolism, to be expelled from the blood into the lungs to be exhaled. This process is crucial for maintaining the body’s oxygen supply and removing carbon dioxide to maintain acid-base balance and overall respiratory health.

Understanding this concept is essential in the context of physiology and the overall functions of the respiratory system, highlighting its importance in sustaining life and supporting aerobic metabolism. Other options provided do not pertain to the respiratory system and instead relate to different physiological processes, such as digestion, metabolism, and hormonal production, which are irrelevant to the workings of external respiration.