How does internal respiration function?

Internal respiration is the process by which oxygen from the blood is delivered to body cells, and carbon dioxide, a waste product of cellular metabolism, is taken from the cells back into the blood. This exchange occurs at the level of the tissues, where oxygen diffuses out of the capillaries and into the cells, while carbon dioxide produced by the cells diffuses into the blood for transport back to the lungs.

Understanding this process is essential as it highlights the critical role of internal respiration in maintaining cellular function and overall metabolic activity. Through this mechanism, cells receive the oxygen necessary for energy production while simultaneously removing carbon dioxide, thus contributing to homeostasis.

The other options, while relevant to the broader topic of respiration, do not specifically define internal respiration. Gas exchange at the alveoli refers to external respiration, where oxygen is brought into the blood from the lungs and carbon dioxide is expelled. Air filtration through the nose pertains to the function of the upper respiratory tract in preparing air for the lungs. Lastly, blood being pumped from the heart to the lungs describes the circulatory system's role in external respiration, not the exchange that occurs within the tissues. Each of these processes is part of the overall respiratory system, but option B specifically pertains to the definition and function