External respiration includes all of these processes EXCEPT _____. release of carbon dioxide by tissue cells gas transport gas diffusion across respiratory membrane breathing Solution External respiration includes all of these processes except release of carbon dioxide by tissue cells. External respiration occurs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses into the alveolar air. Internal respiration occurs in the tissues where the oxygen diffuses out of the blood and carbon dioxide diffuses out of the cells. Gas exchange takes place by the diffusion process where the movement of the substance from higher concentration to lower concentration of that substance occurs. Gas diffusion occurs across respiratory membrane..