What is the Difference Between Internal and External Respiration?

The difference between internal and external respiration lies in the location where gas exchange occurs and the direction of the partial pressure gradients.

• External Respiration: This occurs in the lungs or gills, where the body takes in oxygen from the atmosphere and releases carbon dioxide. In the lungs, oxygen diffuses into the blood, and carbon dioxide diffuses into the alveolar air down their respective partial pressure gradients. External respiration involves both inhalation and exhalation, bringing air into the lungs and releasing it to the atmosphere.
• Internal Respitation: This occurs in the body tissues, where cells release carbon dioxide and take in oxygen from the blood. In contrast to external respiration, the gases move in the opposite direction, with oxygen diffusing out of the blood into the tissues, and carbon dioxide diffusing out of the tissues into the blood. Internal respiration also occurs as simple diffusion due to a partial pressure gradient.

In summary, external respiration involves gas exchange with the external environment in the lungs, while internal respiration involves gas exchange with the internal environment in the body tissues.

Comparative Table: Internal vs External Respiration

The difference between internal and external respiration can be summarized in the following table:

In internal respiration, oxygen diffuses out of the blood and into the body's tissues, while carbon dioxide diffuses from the tissues into the blood. On the other hand, in external respiration, oxygen is inhaled into the lungs and diffuses into the blood, and carbon dioxide is exhaled from the blood and into the lungs. Both processes are essential for the proper functioning of living organisms.