Question:
What makes the alveolus adapted for efficient gas exchange?
Answer:
The alveolus is the terminal component of the lung. The efficiency of gas exchange across its wall and into the blood is dependent on several factors including; adequate ventilation, adequate blood supply and the structure of the alveolus. Through breathing in and out, we remove carbon dioxide and maintain the partial pressure of oxygen. This maintains the diffusion gradient across the alveolar wall of carbon dioxide out of, and oxygen into, the blood. The blood is continuously replenished, therefore also maintaining the gradient. When breathing or blood flow is obstructed, this reduces the speed at which the CO2 and O2 diffuse out and into the blood and therefore can lead to carbon dioxide retention and/or hypoxia. The efficiency of this diffusion is also dependent on the structure of the alveolus. Gas exchange takes place over a very thin surface, only 1 cell thickness of the epithelial wall of the alveolus and 1 cell thickness of the endothelial wall of the blood vessel. This maintains a short diffusion distance, therefore reducing the time it takes for gas exchange to occur.
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