What is the main focus of internal respiration?

The correct answer highlights that the primary focus of internal respiration is the gas exchange that occurs between the blood and the tissues of the body. This process is crucial because it is where oxygen, which has been transported by the blood after being inhaled in the lungs, is delivered to the cells for metabolic processes. At the same time, carbon dioxide, which is a byproduct of cellular metabolism, diffuses from the tissues into the blood to be carried back to the lungs for exhalation.

In contrast, other processes such as mechanical air movement and gas exchange in the alveoli pertain to external respiration. Mechanical air movement refers to the physical act of breathing and the movement of air into and out of the lungs, while gas exchange in the alveoli specifically involves the exchange of gases (oxygen and carbon dioxide) between the air and the blood. Oxygen uptake in the lungs also relates to external respiration, as it describes the absorption of oxygen into the blood from the alveoli.

Understanding these distinctions helps clarify the specific role of internal respiration in the overall process of respiration and how it supports cellular metabolism throughout the body.