The essential features of alveolar epithelium as a gas exchange surface
Alveoli are tiny air sacs in the lungs. Their walls have special features that allow oxygen and carbon dioxide to diffuse rapidly between air and blood.
Formula
Rate of diffusion ∝ (Surface Area × Concentration Gradient) ÷ Thickness (Fick's Law)
Real World
Premature babies often lack sufficient surfactant — the fluid lining alveoli — causing them to collapse; hospital CPAP machines compensate by maintaining pressure, keeping the gas exchange surface functional.
Exam Focus
Apply Fick's Law explicitly: name surface area, concentration gradient, and thickness as separate points rather than giving a vague 'thin walls' answer.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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