Internal respiration is the process by which oxygen is delivered to the body's cells and carbon dioxide is removed. This occurs at the cellular level, where oxygen is used to produce energy through a process called cellular respiration. The cells take in oxygen from the blood and release carbon dioxide as a waste product. During internal respiration, oxygen diffuses from the blood into the cells, while carbon dioxide moves from the cells into the blood. This exchange is crucial for maintaining the body's energy levels and overall function. Proper internal respiration ensures that cells receive the oxygen they need to perform their vital activities.