Final answer:
Both internal and external respiration depend on the diffusion of oxygen and carbon dioxide across the alveoli and capillaries. Adequate ventilation and perfusion are key for effective gas exchange, and hemoglobin is crucial for oxygen transport in the blood. The body adapts to insufficient ventilation or perfusion by redirecting blood to areas with sufficient oxygen.
Step-by-step explanation:
Both internal and external respiration depend on the process of diffusion to transfer oxygen and carbon dioxide between the alveoli in the lungs and the capillaries in the bloodstream. In external respiration, there is an exchange of gases between the alveoli and the pulmonary capillaries due to partial pressure differences; oxygen diffuses into the blood, while carbon dioxide diffuses out to be expelled from the body. By contrast, internal respiration involves the exchange of gases between the capillaries and body tissues, driven again by differences in partial pressures, with oxygen moving from blood to tissues and carbon dioxide making the reverse journey.
For efficient gas exchange, sufficient ventilation and perfusion are crucial. Ventilation ensures a high partial pressure of oxygen in the alveoli, while perfusion affects the blood flow in the capillaries. If either is insufficient, the body adapts by redirecting blood flow to areas with better ventilation. Hemoglobin plays a pivotal role in transporting oxygen, as it binds oxygen molecules making transport through blood possible. In tissues with lower oxygen levels, the oxygen dissociates from hemoglobin and diffuses into the cells, while hemoglobin, now carrying carbon dioxide which increases its acidity, transports it back to the lungs.