Anatomy and Physiology II Practice Test

The correct choice, external respiration, refers to the gas exchange that takes place in the lungs. This process involves the movement of oxygen from the alveoli (small air sacs in the lungs) into the blood within the pulmonary capillaries. At the same time, carbon dioxide diffuses from the blood into the alveoli to be exhaled. External respiration is crucial for oxygenating the blood and removing carbon dioxide, which is a waste product of metabolism.

Internal respiration, in contrast, occurs at the tissue level where oxygen is delivered to cells and carbon dioxide is collected from them. Pulmonary respiration is a term that may refer to the mechanics of breathing, involving inhalation and exhalation but is not the best terminology to describe gas exchange specifically. Cellular respiration indicates the metabolic processes within cells that use oxygen to convert glucose into energy, producing carbon dioxide as a byproduct. Hence, the process that directly relates to gas exchange within the lungs is identified as external respiration.