Internal respiration is the process by which oxygen is delivered from the blood to the body's cells, and carbon dioxide is removed from the cells to the blood. This exchange occurs in the tissues of the body, where oxygen is used for cellular metabolism, producing energy. The oxygen-rich blood from the lungs travels through the heart and into the capillaries, where it reaches the cells. During internal respiration, cells take in oxygen and release carbon dioxide as a waste product. The carbon dioxide then diffuses into the blood, where it is transported back to the lungs to be exhaled. This process is essential for maintaining the body's energy levels and overall function.