External respiration is the process of gas exchange between the lungs' alveoli and the blood in the pulmonary capillaries. This crucial process allows oxygen to enter the bloodstream and carbon dioxide, a waste product, to be removed from the blood and exhaled.
Here's a breakdown of external respiration:
- Location: External respiration occurs specifically in the alveoli of the lungs. Alveoli are tiny air sacs surrounded by capillaries.
- Gases Involved: The primary gases involved are oxygen (O2) and carbon dioxide (CO2).
- Process:
- Oxygen Uptake: Oxygen from the inhaled air diffuses from the alveoli into the blood within the pulmonary capillaries. This happens because the concentration of oxygen is higher in the alveoli than in the deoxygenated blood.
- Carbon Dioxide Release: Carbon dioxide diffuses from the blood in the pulmonary capillaries into the alveoli. This happens because the concentration of carbon dioxide is higher in the deoxygenated blood than in the alveoli.
- Driving Force: The exchange of gases is driven by differences in partial pressures of oxygen and carbon dioxide between the alveoli and the blood. Essentially, gases move from areas of high concentration to areas of low concentration.
Comparison with Internal Respiration
It's important to distinguish external respiration from internal respiration:
| Feature | External Respiration | Internal Respiration |
|---|---|---|
| Location | Alveoli of the lungs | Tissues throughout the body |
| Process | Exchange of gases between alveoli and pulmonary blood | Exchange of gases between systemic blood and body cells |
| Primary Purpose | Oxygenating the blood; removing CO2 from blood | Delivering O2 to cells; removing CO2 from cells |
In summary, external respiration is the vital process happening in the lungs where oxygen is taken into the blood, and carbon dioxide is released to be exhaled, setting the stage for oxygen transport to the body's tissues and cells via internal respiration.
