Which of the following processes occurs in internal respiration?

The process that occurs in internal respiration is the exchange of gases between blood and body tissues. During internal respiration, oxygen diffuses from the blood into the body cells, where it is used for metabolic processes, while carbon dioxide, a waste product of metabolism, diffuses from the cells into the blood to be transported back to the lungs for exhalation. This process is essential for providing the necessary oxygen to tissues for cellular respiration and removing carbon dioxide to maintain homeostasis.

In contrast, other processes mentioned relate to respiration but do not define internal respiration specifically. For instance, diffusion of carbon dioxide from the blood to the alveoli occurs in external respiration, which involves the exchange of gases between the blood and the lungs. The absorption of oxygen from the lungs into the bloodstream represents the latter part of external respiration, not internal respiration. Lastly, inhalation of air from the atmosphere is also a part of external respiration, focusing on the intake of oxygen before any exchange occurs at the cellular level. Therefore, internal respiration is distinctly characterized by the interaction between blood and tissues, making the choice regarding gas exchange between blood and body tissues the correct answer.