Final answer:
Internal respiration is the gas exchange that occurs at the level of body tissues. It involves the diffusion of gases, specifically oxygen and carbon dioxide, between the blood and the cells of the body.
Step-by-step explanation:
Internal respiration is the gas exchange that occurs at the level of body tissues. It involves the diffusion of gases, specifically oxygen and carbon dioxide, between the blood and the cells of the body. The partial pressure gradients in internal respiration are opposite to those at the respiratory membrane, with oxygen diffusing out of the blood into the tissues, and carbon dioxide diffusing out of the tissues into the blood.