Final answer:
External respiration occurs in the alveoli, while internal respiration occurs in the body tissues. External respiration involves gas exchange between the alveoli and the blood in the pulmonary capillaries, while internal respiration involves gas exchange between the capillaries and the cells.
Step-by-step explanation:
External respiration refers to the gas exchange that occurs in the alveoli between the alveolar air and the blood in the pulmonary capillaries. Oxygen diffuses from the alveoli to the capillary, while carbon dioxide diffuses from the capillary to the alveoli. This process is driven by partial pressure differences between oxygen and carbon dioxide in the alveoli and the blood.
Internal respiration, on the other hand, refers to the gas exchange that occurs in the body tissues between the capillaries and the cells. Oxygen diffuses from the capillary to the cells, while carbon dioxide diffuses from the cells to the capillary. Again, this process is driven by partial pressure differences between oxygen and carbon dioxide in the capillaries and the cells.
So, to summarize, external respiration occurs in the alveoli and involves the exchange of gases between the alveoli and the blood in the pulmonary capillaries, while internal respiration occurs in the body tissues and involves the exchange of gases between the capillaries and the cells.